Engine Control System - Self-Diagnostics: Other

Engine Control System - Self-Diagnostics: Other Pontiac Vibe I

Code Types

There are 3 types of DTC categories

Type "A" Emissions related. The control module illuminates the MIL when the diagnostic runs and fails. The control module records operating conditions at the time the diagnostic fails. The control module stores this information in the freeze frame/failure records.
Type "B" Emissions related. The control module illuminates the MIL on the second consecutive ignition cycle that the diagnostic runs and fails. The control module records operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the failure records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records operating conditions at the time of the failure. The control module writes the operating conditions to the freeze frame and updates the failure records.
Type "C" Non-emissions related. The control module stores the DTC information into memory when the diagnostic runs and fails. The MIL will not illuminate. The driver information center, if equipped, may display a message. The control module records operating conditions at the time the diagnostic fails. The control module stores this information in the failure records.

Hard Failures

Hard failures cause Malfunction Indicator Light (MIL) to illuminate and remain on until problem is repaired. If light illuminates and remains on (light may flash) during vehicle operation. Cause of malfunction must be determined using diagnostic (code) charts. If a sensor fails, PCM will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, the vehicle runs but driveability will not be optimum.

Intermittent Failures

Intermittent failures may cause Malfunction Indicator Light (MIL) to flicker or illuminate and go out after the intermittent fault goes away. However, the corresponding trouble code will be retained in PCM memory. If related fault does not reoccur within a certain time frame, related trouble code will be erased from PCM memory. Intermittent failures may be caused by a sensor connector or wiring related problems. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.

Freeze Frame/Failure Records

The freeze frame/failure records are stored when certain DTCs set. They typically include information to aid in reproducing the driving conditions that were present when a DTC is stored. In addition, the engine parameters are also stored. This stored information can be reviewed and compared to the typical scan tool data list values or to data values taken from a similarly equipped known-good vehicle. See SCAN TOOL DATA LIST . The freeze frame/failure records data will be erased when DTC Information is cleared either with the scan tool or by disconnection of the Powertrain Control Module (PCM), or PCM power supply.

Snapshot

The scan tool Snapshot feature can be triggered to capture and store engine parameters when a malfunction occurs. This stored information can be reviewed and compared to the typical scan tool data values or to data values taken from a similarly equipped known-good vehicle.

SERVICE BAY TESTS

The Service Bay Tests are included on the scan tool for some systems depending upon vehicle make and model. Service bay tests initiate operation of certain PCM controlled functions, assisting the technician in system diagnosis.

EVAP Purge/Seal Function

Note. Ensure vehicle underbody temperature is similar to ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. Fuel tank pressure may increase on a hot vehicle due to thermal expansion of vapors in fuel tank. Fuel tank fill levels can affect the results of the diagnostic procedure. Fuel tank pressure may increase on a warm vehicle that has less than one third a tank of fuel.

EVAP purge/seal function is designed to seal the EVAP system with a vacuum applied. The test allows the technician to monitor Fuel Tank Pressure (FTP) sensor, for any vacuum decay. The purge/seal function can also alert the technician of an inoperable purge, vent, or pressure switching solenoid. When the EVAP purge/seal function is enabled, PCM commands vent and pressure switching solenoids ON (closed). The purge solenoid is commanded ON (open) allowing a vacuum to enter EVAP system. After 30 seconds, PCM commands purge solenoid OFF (closed), sealing the system. EVAP system will remain sealed for 150 seconds. FTP sensor reading should be approximately -12.50 in. H2O. To perform EVAP purge/seal test with the scan tool follow the procedures below

Run engine to normal operating conditions.
Install scan tool.
Turn ignition switch to RUN position, engine OFF.
Remove fuel fill cap. FTP sensor should read near 0.0 in. H2O.
Install fuel fill cap and start the engine.
Enable EVAP purge/seal function on the scan tool.
FTP sensor reading should decrease to a -12.50 in. H2O, indicating a vacuum has entered the system.
Observe FTP sensor reading for 2 minutes. If there is no evidence of vacuum decay, FTP sensor reading should remain at -12.50 in. H2O.

Check Mode

Note. DO NOT turn OFF the ignition anytime during or after the operation of the vehicle in CHECK MODE. Observe and capture all CHECK MODE operation DTC and FREEZE FRAME information on scan tool before turning ignition OFF. Any DTC or freeze frame information that occurred during check mode operation will be cleared by the PCM when ignition is turned OFF.

Check mode can be used to increase the ability of the Powertrain Control Module (PCM) to detect engine control system malfunctions. PCM can be requested to operate in CHECK MODE by using OUTPUT CONTROLS feature of the scan tool. While in CHECK MODE operation, PCM will illuminate Malfunction Indicator Light (MIL) and record freeze frame data even on the first failure of a "B" type DTC. Not all engine control system diagnostics will be enhanced by check mode operation. The check mode service bay test can be performed while driving the vehicle to duplicate the customer concern. Those diagnostics most commonly known to benefit from check mode operation will be specified in the diagnostic procedure.

To activate the enhanced diagnostics of check mode operation, perform the following procedure

Capture or save any DTC or freeze frame information on the scan tool before entering CHECK MODE operation. All DTC and freeze frame information will be cleared by PCM when CHECK MODE is entered.
Turn ignition switch to RUN position, engine OFF.
Using scan tool, enter CHECK MODE operation from SPECIAL FUNCTIONS menu. Verify MIL is flashing which indicates check mode request was received and accepted.
Return to DATA LIST selection on the scan tool.
DO NOT turn OFF the ignition after requesting CHECK MODE operation with a scan tool. PCM will return to NORMAL MODE operation when the ignition is cycled from ON to OFF to ON.
Start engine.
Operate vehicle within conditions under which the original concern was noted or within freeze frame conditions that set the DTC.
The DIAGNOSTIC MODE parameter in scan tool data list can be viewed at anytime to verify the vehicle is still operating in CHECK MODE. See «SCAN TOOL DATA LIST»(ref-152429-S11741660572003021000000) .
If MIL illuminates while in check mode, observe and capture all DTC and freeze frame information with the scan tool.
CHECK MODE operation can be terminated by cycling the ignition switch, or commanding NORMAL MODE with the scan tool.

PROGRAMMING

CAUTION

Turn the ignition OFF when installing or removing the PCM connectors and disconnecting or reconnecting the power to the PCM (battery cable, PCM pigtail, PCM fuse, jumper cables, etc.) to prevent internal PCM damage.

Note. Service of the Powertrain Control Module (PCM) consists of a complete replacement of the PCM. There are no serviceable parts, such as programmable read-only memory (PROM) or erasable programmable read-only memory (EPROM) to replace inside the PCM. If PCM is determined to be faulty, the PCM is to be replaced as a complete assembly.

DRIVE CYCLES

Note. See INSPECTION/MAINTENANCE SYSTEM CHECK .

Conditions For Updating I/M System Status

Each system requires at least one, and sometimes several, diagnostic tests. The results of these tests are reported by a Diagnostic Trouble Code (DTC). A system monitor is complete when either all DTCs comprising the monitor have Run and Passed, or any one of the DTCs comprising the monitor have illuminated the MIL. Once all tests are completed, the I/M System Status display will indicate YES in the COMPLETED column. For example, when HO2S Heater Test indicates YES, all oxygen sensor heaters have been diagnosed. If vehicle has 4 heated oxygen sensors, all 4 heater circuits have been diagnosed. I/M SYSTEM STATUS will indicate NO under the COMPLETED column when any required tests for that system have not run. The following is a list of conditions that would set the I/M SYSTEM STATUS indicator to NO

Vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.
Battery has been disconnected or discharged below operating voltage.
Control module power or ground has been interrupted.
Control module has been reprogrammed.
Control module DTCs have been cleared as part of a service procedure.

Monitored Emission Control Systems

The OBD-II system monitors all emission control systems that are on-board. Not all vehicles have a full complement of emission control systems. For example, a vehicle may not be equipped with AIR or EGR. The OBD-II regulations require monitoring of the following

Air conditioning system.
Catalytic converter efficiency.
Comprehensive component monitoring - emission related inputs and outputs.
Evaporative Emissions (EVAP) system.
Exhaust Gas Recirculation (EGR) system.
Fuel Delivery system.
Heated catalyst monitoring.
Misfire monitoring.
Oxygen Sensor (O2S or HO2S) system.
Oxygen Sensor Heater (HO2S Heater) system.
Secondary Air Injection (AIR) system.

For the specific DTCs required for each system, refer to INSPECTION/MAINTENANCE SYSTEM DTCS . Systems such as fuel delivery, misfire, and comprehensive components may not be listed in a system status list. These tests run continuously on some vehicles and may not require an indicator.

SUMMARY

If no Diagnostic Trouble Codes (DTC) are present and a no-start condition exists, proceed to NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 1.8L VIBE article. If no DTCs are present and a driveability condition exists, proceed to TROUBLE SHOOTING - NO CODES - 1.8L VIBE article for diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).

MIL INOPERATIVE

Note. For circuit reference, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .