Ford Escape: Electronic Engine Controls / Description and Operation - Electronic Engine Controls - System Operation and Component Description

System Operation

Comprehensive Component Monitor (CCM)

The comprehensive component monitor (CCM) checks for concerns in any powertrain electronic component or circuit that provides input or output signals to the PCM that can affect emissions and is not monitored by another OBD monitor. Inputs and outputs are, at a minimum, monitored for circuit continuity or correct range of values. Where feasible, inputs are checked for rationality and outputs are checked for correct functionality.

The CCM covers many components and circuits and tests them in various ways depending on the hardware, function, and type of signal. For example, analog inputs such as throttle position or engine coolant temperature are typically checked for opens, shorts, and out of range values. This type of monitoring is carried out continuously. Some digital inputs like brake switch or crankshaft position rely on rationality checks that are checking to see if the input value makes sense at the current engine operating conditions. These types of tests may require monitoring several components and can only be carried out under the appropriate test conditions.

Outputs such as coil drivers are checked for opens and shorts by monitoring a feedback circuit or smart driver associated with the output. Other outputs, such as relays, require additional feedback circuits to monitor the secondary side of the relay. Some outputs are also monitored for correct function by observing the reaction of the control system to a given change in the output command. An idle air control solenoid can be functionally tested by monitoring the idle RPM relative to the target idle RPM . Some tests can only be carried out under the appropriate test conditions. For example, the transmission shift solenoids can only be tested when the PCM commands a shift.

The following is an example of some of the input and output components monitored by the CCM. The component monitor may belong to the engine, ignition, transmission, air conditioning, or any other PCM supported subsystem.

• Inputs: Air conditioning pressure (ACP) transducer sensor, CMP sensor, CKP sensor, ECT sensor, fuel tank pressure (FTP) sensor, IAT sensor, MAF sensor, TP sensor.
• Outputs: EVAP purge valve, EVAP canister vent valve, fuel injector, fuel pump (FP), shift solenoid, TCC solenoid, VCT actuator, wide open throttle A/C cutout (WAC).
• The CCM is enabled after the engine starts and is running. A DTC is stored in KAM and the MIL is illuminated after 2 driving cycles when a concern is detected. Many of the CCM tests are also carried out during an on demand self-test.

Computer Controlled Shutdown

The PCM controls the PCM power relay when the ignition is turned to the ON or START position, by grounding the PCMRC circuit. After the ignition is turned to the OFF, ACC or LOCK position, the PCM stays powered up until the correct engine shutdown occurs.

The ISP-R and the INJPWRM circuits provide the ignition state input to the PCM . Based on the ISP-R and INJPWRM signals the PCM determines when to power down the PCM power relay.

Engine Off Timer Monitor

The engine off time is obtained from the PCM or the BCM . If the engine off time is obtained from the BCM , the PCM expects to receive a message with the engine off time from the BCM shortly after engine start up. If the message is not available on the CAN or a battery disconnect has occurred, a communication DTC sets.

There are two parts to this test.

The first part determines if the timer is incrementing during engine OFF. The PCM determines the timer is incrementing during engine OFF by comparing the engine coolant temperature value prior to shut down, to the engine coolant temperature value at ignition ON to determine if an engine OFF soak has occurred. For an engine OFF soak to occur, the engine coolant temperature value must be greater than 71°C (160°F) while the engine is running. The timer starts at ignition OFF and the engine coolant temperature value must decrease by greater than 17°C (30°F) before the next ignition ON signal. If the engine off timer indicates a value less than 30 seconds, a DTC sets.

The second part checks the accuracy of the engine off timer. The PCM determines the accuracy of the engine off timer by comparing time in the BCM with the time in the PCM . The timer in the BCM is allowed to count up for 5 minutes and compared to a different clock in the PCM . If the two timers differ by more than 15 seconds, a DTC sets.

Engine RPM Limiter

The PCM disables some or all of the fuel injectors whenever an engine RPM over speed condition is detected. The purpose of the engine RPM limiter is to prevent damage to the powertrain. Once the driver reduces the excessive engine speed, the engine returns to the normal operating mode. No repair is required. However, the technician should clear the diagnostic trouble codes (DTCs) and inform the customer of the reason for the DTC .

Excessive wheel slippage may be caused by sand, gravel, rain, mud, snow, ice, or excessive and sudden increase in RPM while in NEUTRAL or while driving.

Failure Mode Effects Management (FMEM)

The failure mode effects management (FMEM) is an alternate system strategy in the PCM designed to maintain engine operation if one or more sensor inputs fail.

When a sensor input is determined to be out of limits by the PCM , an alternative strategy is initiated. The PCM substitutes a fixed value for the incorrect input and continues to monitor the suspect sensor input. If the suspect sensor begins to operate within limits, the PCM returns to the normal engine operational strategy.

Flash Electrically Erasable Programmable Read Only Memory (EEPROM)

The flash EEPROM is an integrated circuit within the PCM . This integrated circuit contains the software code required by the PCM to control the powertrain. One feature of the EEPROM is that it can be electrically erased and then reprogrammed through the DLC without removing the PCM from the vehicle.

Hybrid Diagnostic Modes

Engine Running Diagnostic Mode

The engine running diagnostic mode is a PCM strategy which is separate from the normal operating strategy. When in this mode, the engine is running and does not turn off, as it does during normal operation. The engine RPM may be increased to the desired speed as the vehicle is in the pedal follower mode. To activate the engine running diagnostic mode the gear selector must be in the PARK position, and the ignition cycled to the START position. The engine is allowed to idle as long as the powertrain and hybrid electric systems operate within the calibrated limits. This mode is helpful whenever the engine must stay running for diagnostics and repairs that require the engine to be idling for extended time. Carry out the following sequence to activate this mode:

• apply the parking brake
• place the gear selector in the PARK position
• ignition in the OFF position

• NOTE: Do not start the engine.

• ignition in the ON position with the engine OFF
• within 5 seconds of the ignition in the ON position, fully apply the accelerator pedal and hold for 10 seconds
• within 5 seconds, release the accelerator pedal, cycle the ignition to the ON/RUN position, fully apply the accelerator pedal and hold the engine RPM at the REV limiter, approximately 4,000 RPM , for 10 seconds until the green READY indicator turns OFF, then release the accelerator pedal
• within 5 seconds release the accelerator pedal, shift the gear selector to the DRIVE position and fully apply the accelerator pedal
• hold the accelerator pedal fully applied for 10 seconds
• release the accelerator pedal and shift the gear selector to the PARK position

If the sequence is correctly executed the powertrain malfunction indicator (wrench) flashes once per second when the gear selector is shifted to the PARK position. The engine may be started by cycling the ignition to the START position. The PCM exits the engine running mode when the gear selector is shifted to any gear other than PARK, when the ignition is turned to the OFF or ACC position, or the powertrain or hybrid electric system exceeds calibrated limits.

Engine Cranking Diagnostic Mode

NOTE: Access the BECM and monitor the high voltage traction battery state of charge PID . If the monitored PID displays the state of charge below 45%, run the vehicle in the Engine Running Diagnostic Mode to raise the BECM state of charge. When the high voltage traction battery state of charge exceeds 45%, the engine cranking diagnostic mode can be activated.

The engine cranking diagnostic mode is a PCM strategy which is separate from the normal operating strategy. It allows the engine to crank in a similar fashion as a conventional vehicle with the fuel disabled. When in this mode, the PCM commands the TCM to spin the generator which cranks the engine with the speed between 900 and 1,200 RPM . To activate the engine cranking diagnostic mode the gear selector must be in the PARK position, the high voltage traction battery state of charge must be greater than 45%, and the ignition must be cycled to the START position. The engine cranks as long as the high voltage traction battery state of charge stays greater than 35%. The hazard indicator (red triangle) flashing once per second indicates the vehicle is in the engine cranking diagnostic mode. In this mode the throttle plates can be moved from closed to open by applying and holding the brake pedal before applying the accelerator pedal. After moving the throttle plate position twice, function may be disabled and DTC P2111 may set. To carry out this function again, clear the DTC s and enter this mode again. This mode is helpful whenever the engine must be cranked but not started. Carry out the following sequence to activate this mode:

• apply the parking brake
• place the gear selector in the PARK position
• ignition in the OFF position

• NOTE: Do not start the engine.

• ignition in the ON position with the engine OFF
• within 5 seconds of the ignition in the ON position, fully apply the accelerator pedal and hold for 10 seconds
• within 5 seconds release the accelerator pedal, shift the gear selector to the REVERSE position and fully apply the accelerator pedal
• hold the accelerator pedal fully applied for 10 seconds
• release the accelerator pedal and shift the gear selector to the PARK position

If the sequence is correctly executed the hazard indicator (red triangle) flashes once per second when the gear selector is shifted to the PARK position. The engine may be cranked by cycling the ignition to the START position. If the ignition stays in the START position for 15 seconds or longer, the PCM may set the DTC P2535. The PCM exits the engine cranking diagnostic mode when the high voltage traction battery state of charge drops below 35%, the gear selector is shifted to any gear other than PARK, or when the ignition is turned to the OFF or ACC position.

Intermittent Diagnostic Techniques

Intermittent diagnostic techniques help find and isolate the root cause of intermittent concerns associated with the EEC ) system. The information is organized to help find the concern and carry out the repair. The process of finding and isolating an intermittent concern starts with recreating a fault symptom, accumulating PCM data, and comparing that data to typical values, then analyzing the results. Refer to the scan tool manufacturer's instruction manual for the functions described below.

Before proceeding, be sure that:

• Customary mechanical system tests and inspections do not reveal a concern. Mechanical component conditions can make a PCM system react abnormally.
• TSB and OASIS messages, if available, are reviewed.
• Quick Test and associated diagnostic subroutines have been completed without finding a concern, and the symptom is still present.

Recreating the Fault

Recreating the concern is the first step in isolating the cause of the intermittent symptom. If freeze frame data is available, it may help in recreating the conditions at the time of a MIL DTC . Listed below are some of the conditions for recreating the concern:

  CONDITIONS TO RECREATE FAULT

Accumulating PCM Data

PCM data can be accumulated in a number of ways. This includes circuit measurements with a DMM or scan tool PID data. Acquisition of PCM PID data using a scan tool is one of the easiest ways to gather information. Gather as much data as possible when the concern is occurring to prevent improper diagnosis. Data should be accumulated during different operating conditions and based on the customer description of the intermittent concern. Compare this data with the known good data values.

Peripheral Inputs

Some signals may require certain peripherals or auxiliary tools for diagnosis. In some cases, these devices can be inserted into the measurement jacks of the scan tool or DMM . For example, connecting an electronic fuel pressure gauge to monitor and record the fuel pressure voltage reading and capturing the data would help find the fault.

Comparing PCM Data

After the PCM values are acquired, it is necessary to determine the concern area. This typically requires the comparison of the actual values from the vehicle to known good data values.

Analyzing PCM Data

Look for abnormal events or values that are clearly incorrect. Inspect the signals for abrupt or unexpected changes. For example, during a steady cruise most of the sensor values should be relatively stable. Sensors such as TP , as well as an RPM that changes abruptly when the vehicle is traveling at a constant speed, are clues to a possible concern area.

Look for an agreement in related signals. For example, if the APP1 or APP2 changes during acceleration, a corresponding change should occur in RPM and SPARK ADV PID .

Make sure the signals act in proper sequence. An increase in RPM after the TP1 and TP2 increases is expected. If the RPM increases without a TP1 and TP2 change, a concern may exist.

The PID values are not always captured from the same execution loop. Depending on the number of PID s acquired, the sample rate may be 60 ms or longer. For example, the ETC_ACT reading will always lag behind the ETC_DSD reading due to the physical time to move the throttle plate. This is an expected difference between ETC_ACT and ETC_DSD during these events.

Scroll through the PID data while analyzing the information. Look for sudden drops or spikes in the values.

International Standards Organization (ISO) 14229 Diagnostic Trouble Code (DTC) Descriptions

The ISO 14229 is a global, diagnostic communication standard. The ISO 14229 is a set of standard diagnostic messages that can be used to diagnose any vehicle module in use and at the assembly plant. The ISO 14229 is similar to the Society of Automotive Engineers (SAE) J2190 diagnostic communication standard that was used by all Original Equipment Manufacturers (OEMs) for previous communication protocols.

The ISO 14229 changes the way PIDs, DTCs, and OSC is processed internally in the PCM and in the scan tool software. Most of the changes are to make data transfer between electronic modules more efficient, and the amount and type of information that is available for each DTC . This information may be helpful in diagnosing driveability concerns.

Historical Diagnostic Trouble Codes (DTCs)

Historical DTCs use bit 5 (the DTC test failed at least once since last code clear) to indicate that a DTC is no longer confirmed or pending, but has failed at least once since the last time the DTCs were cleared. The bit 5 is designed to eventually age out and clear in 80 drive cycles (255 in the future). The scan tool does not allow a technician to retrieve historical DTCs unless there are no active DTCs present. This information, in conjunction with manufacturer freeze frame and snapshot data, may be useful in diagnosing a noticeable fault that did not progress to MIL status, or an extended amount of time has occurred before diagnosis, and the confirmed DTC has cleared.

DTC Structure

Like all digital signals, DTCs are sent to the scan tool as a series of 1s and 0s. Each DTC is made up of 2 data bytes, each consisting of 8 bits that can be set to 1 or 0. In order to display the DTCs in the conventional format, the data is decoded by the scan tool to display each set of 4 bits as a hexadecimal number (0 to F). For example, P0420 Catalyst System Efficiency Below Threshold (Bank 1).

The table below shows how to decode the bits into hex digits.

The first 4 bits of a DTC do not convert directly into hex digits. The conversion into different types of DTCs (P, B, C and U) is defined by SAE J2012. This standard contains DTC definitions and formats.

ISO 14229 sends 2 additional bytes of information with each DTC , a failure type byte and a status byte.

All ISO 14229 DTCs are 4 bytes long instead of 3 or 2 bytes long. Additionally, the status byte for ISO 14229 DTCs is defined differently than the status byte for previous applications with 3 byte DTCs.

Failure Type Byte

The failure type byte is designed to describe the specific failure associated with the basic DTC . For example, a failure type byte of 1C means circuit voltage out of range, 73 means actuator stuck closed. When combined with a basic component DTC , it allows one basic DTC to describe many types of failures.

For example, P0110:1C-AF means intake air temperature (IAT) sensor circuit voltage out of range. The base DTC , P0110, means IAT sensor circuit, while the failure type byte 1C means circuit voltage out of range. This DTC structure was designed to allow manufacturers to more precisely identify different kinds of faults without always having to define new DTC numbers.

The PCM does not use failure type bytes and always sends a failure type byte of 00 (no sub type information). This is because OBD II regulations require manufacturers to use 2 byte DTCs for generic scan tool communications. Additionally, the OBD II regulations require the 2 byte DTCs to be very specific, so there is no additional information that the failure type byte could provide.

A list of failure type bytes is defined by SAE J2012 but is not described here because the PCM does not use the failure type byte.

Status Byte

The status byte is designed to provide additional information about the DTC , such as when the DTC failed, when the DTC was last evaluated, and if any warning indication has been requested. Each of the 8 bits in the status byte has a precise meaning that is defined in ISO 14229.

The protocol is that bit 7 is the most significant and left most bit, while bit 0 is the least significant and right most bit.

DTC Status Bit Definitions

Refer to the following status bit descriptions:

Bit 7

• 0 - The ECU is not requesting warning indicator to be active
• 1 - The ECU is requesting warning indicator to be active

Bit 6

• 0 - The DTC test completed this monitoring cycle
• 1 - The DTC test has not completed this monitoring cycle

Bit 5

• 0 - The DTC test has not failed since last code clear
• 1 - The DTC test failed at least once since last code clear

Bit 4

• 0 - The DTC test completed since the last code clear
• 1 - The DTC test has not completed since the last code clear

Bit 3

• 0 - The DTC is not confirmed at the time of the request
• 1 - The DTC is confirmed at the time of the request

Bit 2

• The DTC test completed and was not failed on the current or previous monitoring cycle
• 1 - The DTC test failed on the current or previous monitoring cycle

Bit 1

• 0 - The DTC test has not failed on the current monitoring cycle
• 1 - The DTC test failed on the current monitoring cycle

Bit 0

• 0 - The DTC is not failed at the time of request
• 1 - The DTC is failed at the time of request

For DTCs that illuminate the MIL, a confirmed DTC means the PCM has stored a DTC and has illuminated the MIL. If the fault has corrected itself, the MIL may no longer be illuminated but the DTC still shows a confirmed status for 40 warm up cycles at which time the DTC is erased.

For DTCs that do not illuminate the MIL, a confirmed DTC means the PCM has stored a DTC . If the fault has corrected itself, the DTC still shows a confirmed status for 40 warm up cycles at which time the DTC is erased.

To determine if a test has completed and passed, such as after a repair, information can be combined from 2 bits as follows:

If bit 6 is 0 (the DTC test completed this monitoring cycle), and bit 1 is 0 (the DTC test has not failed on the current monitoring cycle), then the DTC has been evaluated at least once this drive cycle and was a pass.

If bit 6 is 0 (the DTC test completed this monitoring cycle) and bit 0 is 0 (the DTC test is not failed at the time of request), then the most recent test result for that DTC was a pass.

The status byte bits can be decoded as a 2 digit hexadecimal number, and displayed as the last 2 digits of the DTC , for example for DTC P0110:1C-AF, AF represents the status byte info.

Malfunction Indicator Lamp (MIL)

The MIL notifies the driver the PCM has confirmed an OBD emission related component or system concern. When this occurs, an OBD DTC sets.

• The MIL is located in the IPC and is the international standards organization (ISO) standard engine symbol.
• The MIL is illuminated with the ignition ON, engine OFF, until the engine is cranked for starting. The MIL will turn OFF after engine start if no concerns are present.
• The MIL may flash after 17 seconds with the ignition ON, engine OFF, unless the OBD inspection/maintenance (I/M) readiness indicators indicate all of the OBD monitors have completed since the last KAM reset or since the PCM DTCs have been cleared with a reset command from the scan tool.
• The MIL will remain illuminated after engine start if a confirmed emission related concern or an OBD DTC exists.
• If the MIL flashes at a steady rate, after engine start, a severe misfire condition may exist.
• The MIL will remain OFF with the ignition ON, engine OFF, if a MIL indicator or IPC concern is present.
• To turn OFF the MIL after a repair, a reset command from the scan tool must be sent, or 3 consecutive drive cycles must be completed without a concern.
• If the MIL flashes erratically, a low battery voltage concern may be present causing the PCM to reset during cranking.

On Board Diagnostic (OBD) Drive Cycle

Description of On Board Diagnostic (OBD) Drive Cycle

The following procedure is designed to execute and complete the OBD monitors. To complete a specific monitor for repair verification, follow steps 1 through 4, then continue with the step described by the appropriate monitor found under the OBD Monitor Exercised column.

Federal OBD requires that all vehicles comply with 0.5 mm (0.020 inch) EVAP system requirements in addition to meeting the 1.0 mm (0.040 inch) EVAP system monitoring requirements. Some vehicles will use the engine off 0.5 mm (0.020 inch) EVAP monitor rather than the 1.0 mm (0.040 inch) EVAP monitor to set I/M Readiness.

For the EVAP system monitor to run, the ambient air temperature must be between 4.4 to 37.8°C (40 to 100°F), and the altitude below 2,438 meters (8,000 feet). If the OBD monitors must be completed in these conditions, the PCM must detect them once (twice on some applications) before the EVAP system monitor can be bypassed and OBD monitors readied. The EVAP Monitor Bypass procedure is described in the following drive cycle.

Use a scan tool to carry out the OBD drive cycle. Refer to the scan tool manufacturer's instruction manual for each described function.

Drive Cycle Recommendations

NOTICE: Strict observance of posted speed limits and attention to driving conditions are mandatory when proceeding through the following drive cycles. Failure to follow these instructions may result in personal injury.

• Most OBD monitors complete more readily using a steady foot driving style during cruise or acceleration modes. Operating the throttle in a smooth fashion minimizes the time required for monitor completion.
• The fuel tank level should be between 1/2 and 3/4 full with 3/4 full being the most desirable.
• The EVAP purge flow monitor can operate only during the first 30 minutes of engine operation. When executing the procedure for this monitor, stay in part throttle mode and drive in a smooth fashion to minimize fuel slosh.
• The EVAP 0.508 mm (0.020 inch) leak check monitor runs after the ignition is turned OFF. The vehicle must be driven to complete the EVAP purge flow monitor to increase the temperature of the fuel in the fuel tank.
• When bypassing the EVAP engine soak times, the PCM must remain powered (ignition ON) after clearing the continuous DTC s and relearning emission diagnostic information.

For best results, follow each of the following steps as accurately as possible:

On Board Diagnostics (OBD) Monitors

OBD I, OBD II And Engine Manufacturer Diagnostics (EMD) Overview

The California Air Resources Board (CARB) began regulating OBD systems for vehicles sold in California beginning with the 1988 model year. The initial requirements, known as OBD I, required identifying the likely area of concern with regard to the fuel metering system, exhaust gas recirculation (EGR) system, emission related components and the PCM. A malfunction indicator lamp (MIL) was required to illuminate and alert the driver of the concern and the need to repair the emission control system. A DTC was required to assist in identifying the system or component associated with the concern.

Starting with the 1994 model year, both CARB and the Environmental Protection Agency (EPA) mandated enhanced OBD systems, commonly known as OBD II. The objectives of the OBD II system are to improve air quality by reducing high in use emissions caused by emission related concerns, reducing the time between the occurrence of a concern and its detection and repair, and assisting in the diagnosis and repair of emission related problems.

OBD I Systems

OBD I vehicles use the same PCM, controller area network (CAN) serial data communication link, J1962 Data Link Connector, and PCM software as the corresponding OBD II vehicle. The only difference is the possible removal of the rear oxygen sensors, fuel tank pressure (FTP) sensor, EVAP canister vent valve, and a different PCM calibration. Starting in the 2006 model year, all Federal vehicles from 8,500 to 14,000 lbs. Gross Vehicle Weight Rating (GVWR) will have been phased into OBD II and OBD I systems will no longer be utilized in vehicles up to 14,000 lbs. GVWR.

OBD II Systems

The OBD II system monitors virtually all emission control systems and components that can affect tailpipe or evaporative emissions. In most cases, concerns must be detected before emissions exceed 1.5 times the applicable 120,000 or 150,000 mile emission standards. Partial zero emission vehicles (PZEV) and super ultra low emission vehicles (SULEV-II) can use 2.5 times the standard in place of the 1.5 times the standard. If a system or component exceeds emission thresholds or does not operate within a manufacturer's specifications, a DTC is stored and the MIL is illuminated within 2 drive cycles.

The OBD II system monitors for concerns either continuously (regardless of driving mode) or non-continuously (once per drive cycle during specific drive modes). A pending DTC is stored in the PCM keep alive memory (KAM) when a concern is initially detected. Pending DTCs are displayed as long as the concern is present. OBD regulations require a complete concern free monitoring cycle to occur before erasing a pending DTC . This means that a pending DTC is erased on the next power up after a concern free monitoring cycle. However, if the concern is still present after 2 consecutive drive cycles, the MIL is illuminated. Once the MIL is illuminated, 3 consecutive drive cycles without a concern being detected are required to extinguish the MIL. The DTC is erased after 40 engine warm up cycles once the MIL is extinguished.

In addition to specifying and standardizing much of the diagnostics and MIL operation, OBD requires the use of a standard data link connector (DLC), standard communication links and messages, standardized DTCs and terminology. Examples of standard diagnostic information are freeze frame data and inspection/maintenance (I/M) readiness indicators.

Freeze frame data describes data stored in KAM at the point the concern is initially detected and the pending DTC is stored. Freeze frame data consists of parameters such as engine RPM, engine load, vehicle speed or throttle position. Freeze frame data is updated when the concern is detected again on a subsequent drive cycle and a confirmed DTC is stored; however, a previously stored freeze frame is overwritten if a higher priority fuel or misfire concern is detected. This data is accessible with the scan tool to allow duplicating the conditions when the concern occurred in order to assist in repairing the vehicle.

OBD I/M readiness indicators show whether all of the OBD monitors have been completed since the last time the KAM or the PCM DTCs have been cleared. Ford vehicles blink the MIL after 15 seconds of ignition ON engine OFF time to indicate that some monitors have not completed. In some states, it may be necessary to carry out an OBD check in order to renew a vehicle registration. The I/M readiness indicators must show that all monitors have been completed prior to the OBD check.

Starting in the 1996 model year, OBD II was required on all California and California State gasoline engine vehicles up to 14,000 lbs. GVWR. Starting in the 1997 model year, diesel engine vehicles up to 14,000 lbs. GVWR required OBD II.

California states are ones that have adopted California emission regulations, starting in the 1998 model year. For example, Delaware, Connecticut, Maine, Massachusetts, New Mexico, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont and Washington have adopted California's emission regulations. These states receive California certified vehicles for passenger cars, light trucks, and medium duty vehicles up to 14,000 lbs GVWR.

Starting in the 1996 model year, OBD II was also required on all Federal gasoline engine vehicles up to 8,500 lbs. GVWR. Starting in the 1997 model year, diesel engine vehicles up to 8,500 lbs. GVWR required OBD II.

Starting in the 2004 model year, Federal vehicles over 8,500 lbs. are required to phase in OBD II. Starting in the 2004 model year, gasoline fueled medium duty passenger vehicles (MDPVs) are required to have OBD II. By the 2006 model year, all Federal vehicles from 8,500 to 14,000 lbs. GVWR will have been phased into OBD II.

Variable Camshaft Timing (VCT) Monitor

The VCT output driver in the PCM is checked electrically for opens or shorts. The VCT system is checked functionally by monitoring the closed loop camshaft position error correction. If the correct camshaft position cannot be maintained and the system has an advance or retard error greater than the calibrated threshold, a VCT control concern is indicated.

Component Description

Camshaft Position (CMP) Sensor

The CMP sensor detects the position of the camshaft. The CMP sensor identifies when piston number 1 is on its compression stroke. A signal is then sent to the PCM and used for synchronizing the sequential firing of the fuel injectors. Coil on plug (COP) ignition applications use the CMP sensor signal to select the correct ignition coil to fire.

Engines with 1 camshaft and VCT are equipped with 1 CMP sensor. The sensor identifies the camshaft position.

The 1 sensor system on engines with 1 camshaft and with VCT use the following CMP sensor signal circuit names: CMP11 - bank 1, sensor 1.

Crankshaft Position (CKP) Sensor

The CKP sensor is a magnetic transducer mounted on the engine block adjacent to a pulse wheel located on the crankshaft. By monitoring the crankshaft mounted pulse wheel, the CKP sensor is the primary sensor for ignition information to the PCM . The pulse wheel for some V8 engines have a total of 35 teeth spaced 10 degrees apart with 1 empty space for a missing tooth. By monitoring the pulse wheel, the CKP sensor signal indicates crankshaft position and speed information to the PCM . By monitoring the missing tooth, the CKP sensor is able to identify piston travel in order to synchronize the ignition system and provide a way of tracking the angular position of the crankshaft relative to a fixed reference for the CKP sensor configuration. The PCM also uses the CKP sensor signal to determine if a misfire has occurred by measuring rapid decelerations between teeth.

Powertrain Control Module (PCM)

The center of the engine control (EC) system is a microprocessor called the PCM . The PCM receives input from sensors and other electronic components (switches, relays). Based on the information received and programmed into its memory, the PCM generates output signals to control various relays, solenoids and actuators.