Engine Controls - Tests W/codes: Other Pontiac Bonneville IX

HARD FAILURES

Most hard failures cause SERVICE ENGINE SOON light to glow and remain on until malfunction is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. If a sensor fails, control module will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional, but it will most likely display degraded driveability.

INTERMITTENT FAILURES

Intermittent failures cause SERVICE ENGINE SOON light to flicker or glow and go out about 10 seconds after intermittent fault goes away. Corresponding trouble code, however, will be retained in control module memory. If related fault does not reoccur within 50 engine starts, trouble code will be erased from control module memory. Intermittent failures may be caused by sensor, connector or wiring related problems. See INTERMITTENTS in TESTS W/O CODES article in this section.

Field Service Mode Check (If Available)

Note. Vehicles utilizing a 16-terminal DLC or 12-terminal DLC with terminal "B" not used, must use a scan tester for retrieving codes or enter Field Service Mode.

SCAN TESTER USAGE

Note. Before connecting scan tester to vehicle, diagnostic system should be checked to determine if system is operating properly and if information received will be accurate. This is done by performing DIAGNOSTIC CIRCUIT CHECK or ON-BOARD DIAGNOSTIC SYSTEM CHECK located in BASIC TESTING article in this section. If vehicle does not pass diagnostic check, information received may be invalid.

Scan tester is a specialized tester which, when plugged into DLC, can be used to diagnose on-board computer control systems by providing instant access to circuit voltage information without need to crawl under dash or hood to backprobe sensors and connectors.

Scan tester cuts down diagnostic time dramatically by furnishing input data (voltage signals) which can be compared to specification parameters. See SCAN DATA. They may also furnish information on output device (solenoids and motors) status. However, status parameters only indicate output signals have been sent to devices by control module; they do not indicate whether devices have responded properly to signal. Verify proper response at output device using a voltmeter or test light.

A problem may exist even if trouble codes are not present. About 80 percent of driveability problems occur without trouble codes. Sensors that are out of calibration will not set a trouble code but will cause driveability problems.

Using a scan tester is the easiest method of checking sensor specifications and other data parameters. Tester is also useful in finding intermittent wiring problems by wiggling wiring harnesses and connections (key on, engine off) while observing data parameters. See SCAN DATA.

Note. If erroneous voltage signals are suspected, verify tester information using a digital voltmeter and wiring schematic. If non-existent codes are displayed, DO NOT use scan tester for diagnosis. Contact tester manufacturer for additional information.

SCAN DATA

Note. Information contained in SCAN DATA is typical of readings taken on vehicle with engine idling, upper radiator hose hot, closed throttle, transmission in Park or Neutral, "closed loop" status achieved and all accessories off (except as noted in tables). Data parameters are updated a minimum of every 1 1/4 seconds, more often on most models. Not all devices and systems are used on all models; following lists only represent most commonly used parameters. For additional information, refer to owner manual furnished with tester.

SCAN DATA

ECM/PCM CODE CHARTS

Note. In following diagnostic tests, schematics and illustrations

Set Condition

Code P0101 will set when the following conditions are present.

1. Engine is running.
2. No MAF signal for over 4 seconds.

Code P0112 will set when the following conditions are present.

1. Engine coolant temperature is greater than 140°F (60°C).
2. Mass airflow is less than 12 grams per second.
3. Vehicle speed is less than 25 MPH.
4. IAT signal voltage indicates an intake air temperature less than about -29°F (-34°C) for 5 seconds.

Code P0113 will set when the following conditions are present.

1. Signal voltage indicates an intake air temperature greater than 284°F (140°C).
2. Vehicle speed is greater than 35 MPH.
3. Conditions are met for at least for 5 seconds.

Code P0122 will set when the following conditions are present.

1. Ignition on.
2. TP sensor signal voltage is less than about .2 volt for a precalibrated time.

Code P0123 will set when the following conditions are present.

1. TP sensor voltage is greater than 4.8 volts at any time, or engine is running and airflow is less than 17 grams per second.
2. Engine speed is greater than 600 RPM.
3. TP sensor signal voltage is greater than 1.06 volts.
4. Code P0101 is not present.
5. All conditions are met for 5 seconds.

Code P0131 will set when the following conditions are present.

1. Sensor signal voltage remains low (less than closed throttle voltage) for a predetermined amount of time.
2. System is operating in closed loop.

Action Taken

Code P0131 will cause system to operate in open loop.

Code P0132 will set when the following conditions are present.

1. Sensor voltage on signal circuit remains greater than .75 volt for at least 2 minutes while in closed loop.
2. Throttle angle is 2-40 percent.
3. Codes P0122 or P0123 are not set.

Code P0134 will set when the following conditions are present.

1. Engine coolant temperature is greater than 110°F (43°C).
2. Engine run time is more than 40 seconds.
3. Sensor signal voltage is steady at .35-.56 volt.
4. Throttle angle is greater than 3 percent.
5. All conditions are met for about 30 or more seconds.

Code P0171 will set when the following conditions are present.

1. Codes P0101, P0117, P0118, P0122, P0123, P0134, P0501 and P0502 are not set.
2. Engine coolant temperature is between 176°F (80°C) and 230°F (110°C).
3. Steady throttle less than 91 percent.
4. Vehicle speed is less than 70 MPH.
5. On VIN L, engine RPM is between 1000-4000 RPM, or on VIN 1, engine RPM is 0-4000 RPM.
6. EVAP canister purge duty cycle is less than 80 percent.
7. Long term fuel trim is greater than 158.
8. Short term fuel trim is 180.
9. All conditions exist for more than 25 seconds.

Code P0172 will set when the following conditions are present.

1. Codes P0101, P0117, P0118, P0122, P0123, P0501 and P0502 are not set.
2. Engine coolant temperature is between 176°F (80°C) and 230°F (110°C).
3. Steady throttle less than 91 percent.
4. Vehicle speed is less than 70 MPH.
5. On VIN L, engine RPM is 1000-4000 RPM, or on VIN 1, engine RPM is 0-4000 RPM.
6. EVAP canister purge duty cycle is less than 80 percent.
7. Long term fuel trim is less than 100.
8. Short term fuel trim is less than 94.
9. All conditions exist for more than 25 seconds.

Code P0321 will set when the following conditions are present.

1. PCM detects 150 fuel control reference pulses (50 crank revolutions) and no spark reference pulses.
2. Engine speed is less than 1200 RPM.
3. Engine is running.

Fuel reference signal is used by PCM to control ignition timing advance when conditions for setting Code P0321 are present. This condition will cause module mode to be used for ignition timing less than 400 RPM and PCM controlled ignition timing to be degraded less than 1200 RPM.

Code P0325 will set when the following conditions are present.

1. Voltage on signal circuit becomes greater than 3.5 volts or less than 1.5 volts.
2. Either condition is present for 20 seconds.

Code P0325 will set when the following conditions are present.

1. Voltage on signal circuit becomes greater than 3.5 volts or less than 1.5 volts.
2. Either condition is present for 20 seconds.

Code P0341 will set when ratio of fuel control pulses to cam pulses does not equal 6 for 10 occurrences during key cycle.

Monitor Condition

PCM will run EGR test when the following conditions are present.

1. Codes P0122, P0123 or P0501 are not set.
2. Brake has been applied.
3. Engine coolant temperature is greater than 185°F (85°C).
4. Throttle angle is less than one percent.
5. Vehicle speed is greater than 25 MPH.
6. Engine speed is 900-1100 RPM.

Code P0401 will set when PCM does not detect a decrease in engine speed of at least 50 RPM for 6 out of 8 tests. Once 3 tests are run during an ignition cycle, PCM will not run any further flow tests until next ignition cycle. Thus, 3 or more ignition cycles will be necessary to set Code P0401.

Set Condition P0501

Code P0501 will set when the following conditions are present.

1. Engine is running.
2. Code P0703 is not set.
3. Transmission is out of Park or Neutral for more than 4 seconds.
4. Vehicle speed is greater than 18 MPH.
5. Brake is not applied.
6. All conditions are met for 2 seconds.

Set Condition P0502

Code P0502 will set when the following conditions are present.

1. Vehicle speed goes from less than 3 to zero MPH in less than 2 seconds, brake not applied.
2. Engine is running.
3. Engine speed is greater than 3000 RPM.
4. Transmission is out of Park or Neutral for more than 4 seconds.

Code P0703 will set when the following conditions are present.

1. Code P0501 is not present.
2. Vehicle speed has been greater than 35 MPH for 10 seconds and back to zero MPH 5 times.
3. TCC brake switch input status has not changed from released to applied, or applied to released as displayed on scan tester.

Code P0703 Schematic (3.8L) TCC Brake Switch Input. Scheme 71

Code P0703 Diagnostic Flow Chart (3.8L) TCC Brake Switch Input. Scheme 72

Code P0705 will set when the following conditions are present.

1. Ignition is on and engine off.
2. Vehicle speed is zero MPH.
3. PRNDL inputs indicate a gear other than Park and Neutral.
4. All conditions are met for a predetermined time for 3 consecutive start-ups.

or

1. PRNDL inputs status indicators ("P", "A", "B"and "C") indicate an incorrect combination of low and high. PCM will also command stepper motor cruise control to be inhibited.

Code P0712 will set when the following conditions are present.

1. Engine run time is over 2 minutes.
2. Transaxle temperature sensor signal indicates a temperature less than about -40°F (-40°C).
3. Above conditions for over 1.6 second.

Code P0713 will set when the following conditions are present.

1. Engine run time is over one minute.
2. Transaxle temperature sensor signal indicates a temperature greater than 284°F (140°C).
3. All conditions exist for over 1.6 seconds.

Code P0740 will set when the following conditions are present.

1. TP sensor throttle angle greater than 10 percent.
2. Vehicle is in 3rd or 4th gear.
3. VSS signal greater than 35 MPH for a 10 second minimum.
4. TCC is commanded on by PCM.
5. Engine RPM/vehicle speed ratio indicates TCC is not locked.
6. All conditions exist for over 10 seconds.

Code P0755 will set when the following conditions are present.

1. Shift "B" is failed in off position, causing transaxle to be in 4th gear and: - Desired gear is 1st. - Throttle angle is greater than 3 percent. - VSS is greater than 5 MPH. - Codes P0122, P0123, P0501 or P0502 are not set. - Engine speed-to-vehicle speed does not indicate 1st gear. - Conditions exist for 3.5 seconds.

or

1. Shift "B" is failed in on position, causing transaxle to be in 1st gear and: - Desired gear is 4th. - PRNDL is in 3rd 0r 4th. - Throttle angle is greater than 10 percent. - Codes P0122, P0123 or P0705 are not set. - Engine speed-to-vehicle speed does not indicate 4th gear (LV8 less than 80). - Conditions exist for 2 seconds.

Code P0755 Diagnostic Flow Chart "B" (3.8L) Transmission Shift Solenoid. Scheme 73

Code P1257 will set when the following conditions are present.

1. Intake air temperature is greater than 0°F (-18°C).
2. Boost duty cycle less than 100 percent.
3. Engine torque exceeds a calibrated maximum torque value. This value varies depending on commanded gear and engine RPM.
4. Conditions exist for at least 6 seconds.

Code P1350 will set when the following condition is present.

1. IC circuit opens during engine run mode.

Code P1361 will set when following condition is present.

1. IC circuit grounded during start-up.

or

1. PCM not commanding IC mode (open or grounded by-pass circuit) when engine is started.

Code P1406 will set when the following conditions are present.

1. EGR pintle position signal indicates a voltage out of normal range of pintle position sensor, or a signal that is 10 percent greater or less than PCM commanded position.
2. Either condition for up to 20 seconds.

Code will set if switch indicates and open for 3 consecutive start-up cycles or if input circuit is grounded, Code P0703 is not set, transaxle is in 3rd or 4th gear, TCC is locked and conditions exist for one second.

Code P1530 will set when the following conditions are present.

1. Fan request circuit is grounded during first 6 seconds of engine run time.
2. Engine coolant temperature is less than 88°F (31°C).
3. Ambient air temperature is less than 82°F (28°C).
4. RPM is less than 1800.
5. Codes P0101, P0112, P0113, P0117 or P0118 are not set.
6. All conditions must be met at same time.

Code P1530 Schematic (3.8L) A/C Head Pressure Switch. Scheme 74

Code P1530 Diagnostic Flow Chart (3.8L) A/C Head Pressure Switch. Scheme 75

PCM will set Code P1558 when actual servo position is too low when maximum servo is commanded.

Code P1558 will set when the following conditions are present.

1. Throttle angle less than 50 percent.
2. Desired servo position is 90 percent.
3. Actual servo position is less than 2 percent.
4. Above conditions for 3 seconds.

Code P1561 will set when the following conditions are present.

1. Vent driver circuit is shorted to voltage when vent solenoid is commanded off.
2. Vent driver circuit is open.
3. Vent driver circuit is shorted to ground when vent solenoid is commanded on.
4. One of above conditions are met for more than half of a second.

Code P1561 Diagnostic Flow Chart (3.8L) Cruise Vent Solenoid. Scheme 76

Code P1562 will set when the following conditions are present.

1. Solenoid driver circuit is shorted to voltage when vacuum solenoid is commanded off.
2. Solenoid driver circuit is open.
3. Solenoid driver circuit is shorted to ground when vacuum solenoid is commanded on.
4. One of above conditions are met for more than half of a second.

Code P1562 Diagnostic Flow Chart (3.8L) Cruise Vacuum Solenoid. Scheme 77

Code P1565 will set when the following conditions are present.

1. Servo position signal circuit is open, grounded or shorted to voltage.

or

1. Ground circuit (low) is open.

Code P1565 Diagnostic Flow Chart (3.8L) Cruise Servo Position. Scheme 78

Code P1567 will set when the following conditions are present.

1. ON/OFF switch is open between cruise engage switch and PCM.
2. SET/COAST switch is indicated closed for more than 7 1/2 minutes (switch problem).
3. RESUME/ACCEL switch is indicated closed for more than 7 1/2 minutes (switch problem).
4. Cruise brake signal is open to PCM (no change in status of cruise brake switch) when vehicle makes 5 stops from 35 MPH (for more than 10 seconds) down to zero MPH.
5. Any circuit is shorted to voltage.
6. One of the listed conditions are met.

Code P1567 Schematic (3.8L) Cruise Switches Circuit. Scheme 79

Code P1567 Diagnostic Flow Chart (3.8L) Cruise Switches Circuit. Scheme 80

Code P1568 will set when the following conditions are present.

1. Actual servo position is greater than 15 percent above desired servo position of zero percent for one second.

Code P1568 Diagnostic Flow Chart (3.8L) Cruise System Problem (SPS Indicated High). Scheme 81

When Code P1571 is set, PCM will command EBTCM via serial data circuit to set ABS/TCS DTC 75, turn off traction control, and illuminate TRACTION OFF indicator. P1571 does not illuminate Malfunction Indicator Light (MIL).

Code P1573 will set when the following conditions are present.

1. Code P1630 is not set.
2. PCM has detected communication error for .5 second.

When Code P1573 is set, PCM will not be able to communicate with EBTCM. This will cause EBTCM to set ABS DTC 76, disable traction control, and illuminate TRACTION OFF indicator. P1573 does not illuminate Malfunction Indicator Light (MIL).

Code P1599 will set when vehicle has operated in power management mode.

Code P1619 will set when the following condition is present.

1. Oil life monitor reset input circuit is grounded for more than 60 seconds.

P1619 does not illuminate Malfunction Indicator Light (MIL).

Set Condition Code P1626

Code P1626 will set when the following condition is present.

1. Fuel enable signal is lost after engine has started.

Set Condition Code P1629

Code P1629 will set when the following condition is present.

1. Fuel enable signal is not present during crank.

If fuel enable signal is not seen during crank, injectors will be disabled and PCM will store Code P1629, indicating a problem with theft deterrent system or fuel enable input circuit. Code P1629 will result in a cranks but will not run condition. P1629 does not illuminate Malfunction Indicator Light (MIL).

If fuel enable signal is lost while engine is running, PCM will store Code P1626 and vehicle will run normally. As long as Code P1626 is stored, PCM will ignore any absence of fuel enable signal and vehicle will restart and run as long as problem is isolated to fuel enable circuit only. P1626 does not illuminate Malfunction Indicator Light (MIL).

Code P1630 will set when the following condition is present.

1. PCM detects voltage greater than 17.3 volts or less than 9 volts for more than 10 seconds while engine is running.

Code P1640 will set when the following conditions are present.

1. Engine is running.
2. PCM detects an improper voltage level on a circuit connected to QDM No. 1.
3. Brake not applied.
4. All conditions met for 5 seconds.

PCM will illuminate Malfunction Indicator Light (MIL).

Code P1650 will set when the following conditions are present.

1. Engine is running.
2. PCM detects an improper voltage level on a circuit connected to QDM No. 2.
3. Above conditions met for 5 seconds.

Code P1650 will not illuminate Malfunction Indicator Light (MIL).

Code P1670 will set when the following conditions are present.

1. Engine is running.
2. PCM detects an improper voltage level on a circuit connected to QDM No. 4.
3. Conditions are met for 5 seconds.

Code will set if incorrect voltage level is detected on TCC PWM circuit for over 5 seconds.

SUMMARY

If no hard fault codes are present, driveability symptoms exist or intermittent codes exist, proceed to appropriate TESTS W/O CODES article in this section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

3.8L (VIN K, L & 1) PCM Wiring Diagram (1 Of 3). Scheme 82

3.8L (VIN K, L & 1) PCM Wiring Diagram (2 Of 3). Scheme 83

3.8L (VIN K, L & 1) PCM Wiring Diagram (3 Of 3). Scheme 84