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

Test Description

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks to see if PCM recognizes a problem.
2. Voltage reading at sensor harness terminal "A" of less than 4 volts or greater than 6 volts indicates a fault in Mass Airflow (MAF) sensor circuit, or poor connection.
3. Verifies both ignition feed voltage and a good ground circuit are available.

Code P0101 Schematic (3.8L) Mass Air Flow (MAF) Sensor Circuit. Scheme 8

Code P0101 Diagnostic Flow Chart (3.8L) Mass Air Flow (MAF) Sensor Circuit. Scheme 9

Note. Test numbers refer to numbers on diagnostic chart.

1. An open sensor, wire or connection will cause Code P0112 to set. An open circuit would cause scan tester to display about -40°C. This test determines if wiring and PCM are okay.

Code P0112 Schematic (3.8L) IAT Sensor Circuit Low Temperature Indicated. Scheme 10

Code P0112 Flow Chart (3.8L) IAT Sensor Circuit Low Temperature Indicated. Scheme 11

Note. Test numbers refer to numbers on diagnostic chart.

1. Scan tester may be used to diagnose this fault since PCM transmits actual values when fault is present. A grounded circuit will cause tester to display a temperature of about 147°C.
2. If scan tester displays about -40°C with IAT sensor disconnected, PCM and wiring are okay. Replace IAT sensor.

Code P0113 Flow Chart (3.8L) IAT Sensor Circuit High Temperature Indicated. Scheme 12

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0117 exist.
2. Determines if sensor signal circuit is shorted to ground.

Code P0117 Schematic (3.8L) Coolant Temperature Sensor Low Temperature Indicated. Scheme 13

Code P0117 Flow Chart (3.8L) Coolant Temperature Sensor Low Temperature Indicated. Scheme 14

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set code exist.
2. This test will determine if signal circuit is shorted to ground which will cause conditions for Code P0118.
3. This test will determine if sensor circuits are open. If circuits are okay, check connections at PCM and ECT sensor.

Code P0118 Flow Chart (3.8L) Coolant Temperature Sensor High Temperature Indicated. Scheme 15

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0122 exist.
2. Simulates Code P0123 (high voltage). If PCM recognizes high signal voltage and sets Code P0123, PCM and wiring are okay.
3. Simulates a high signal voltage. Checks signal circuit for an open.

Code P0122 Flow Chart (3.8L) Throttle Position Sensor Signal Voltage Low. Scheme 16

Note. Test numbers refer to numbers on diagnostic chart.

1. With closed throttle, ignition on or idling, voltage at PCM TP sensor signal circuit should be about .20-.74 volt.
2. With TP sensor disconnected, TP sensor voltage should decrease and Code P0122 will set. This test verifies that PCM and wiring are okay.
3. Probing ground circuit with a test light check sensor ground circuit. A faulty sensor ground circuit will cause Code P0123 to set.

Code P0123 Flow Chart (3.8L) Throttle Position Sensor Signal Voltage High. Scheme 17

Note. Test numbers refer to numbers on diagnostic chart.

1. Running engine at 1200 RPM keeps oxygen sensor hot to ensure oxygen sensor remains active and can read exhaust oxygen content accurately.
2. Opening sensor signal circuit and grounding sensor low circuit should result in a displayed voltage of .35-.55 volt. If display is still fixed less than .35 volt, fault is a short to ground in signal circuit, or faulty PCM.

Code P0131 Schematic (3.8L) Heated Oxygen Sensor Low Signal Voltage (Lean). Scheme 18

Code P0131 Flow Chart (3.8L) Heated Oxygen Sensor Low Signal Voltage (Lean). Scheme 19

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0132 exist
2. When grounding circuits, scan tester should read less than .35 volt. If display is not as specified, check for short to voltage in signal circuit.

Code P0132 Flow Chart (3.8L) Heated Oxygen Sensor High Signal Voltage (Rich). Scheme 20

Note. Test numbers refer to numbers on diagnostic chart.

1. If conditions necessary to set Code P0132 exist, system will not go into closed loop.
2. This will determine if sensor or wiring is cause of Code P0134.
3. This test checks continuity in reference circuit.

Code P0134 Flow Chart (3.8L) Heated Oxygen Sensor Open Circuit. Scheme 21

Note. Test numbers refer to numbers on diagnostic chart.

1. Visually/physically checking components/systems which may cause a lean condition may determine cause of Code P0171.
2. MAF sensor which causes PCM to read a lower than actual airflow can cause a lean condition, and Code P0171 to set.
3. Check for faults in EVAP purge system that may cause Code P0171 to set.

Code P0171 Diagnostic Flow Chart - 1 Of 2 (3.8L) Fuel Trim Lean. Scheme 22

Code P0171 Diagnostic Flow Chart - 2 Of 2 (3.8L) Fuel Trim Lean. Scheme 23

Note. Test numbers refer to numbers on diagnostic chart.

1. Visually/physically checking components/systems which may cause a rich condition may determine cause of Code P0172.
2. MAF sensor which causes PCM to read a higher then actual airflow can cause a rich condition, and Code P0172 to set.
3. Silicone contamination of Heated Oxygen Sensor (HO2S) can cause a false rich indication that will be sensed by PCM. PCM will then reduce amount of fuel delivered, possibly causing severe driveability symptoms.

Code P0172 Diagnostic Flow Chart - 1 Of 2 (3.8L) Fuel Trim Rich. Scheme 24

Code P0172 Diagnostic Flow Chart - 2 Of 2 (3.8L) Fuel Trim Rich. Scheme 25

Note. Test numbers refer to numbers on diagnostic chart.

1. Verifies short to ground is not present in spark reference circuit, or an open is not present in ignition jumper harness.
2. Ignition control module will ground spark reference signal if a window on harmonic balancer is interfacing with 18X Hall Effect switch. Starter may have to be bumped several times to obtain a voltage reading.
3. Voltage reading should be lower than that obtained with engine not running, indicating a pulsed reference signal.

Code P0321 Schematic (3.8L) Spark Reference Circuit. Scheme 26

Code P0321 Diagnostic Flow Chart (3.8L) Spark Reference Circuit. Scheme 27

Note. Test numbers refer to numbers on diagnostic chart.

1. If Code P0325 is detected, PCM will retard spark timing. If an audible knock is heard from engine, repair internal engine problem. Normally no knock should be detected at idle.
2. PCM applies 5 volts through a pull-up resistor which should be present at knock sensor terminal.
3. Determines if knock sensor is faulty or if knock sensor portion of PROM is faulty.

Code P0325 Schematic (3.8L) Knock Sensor Error (Single Sensor). Scheme 28

Code P0325 Diagnostic Flow Chart (3.8L) Knock Sensor Error (Single Sensor). Scheme 29

Note. Test numbers refer to numbers on diagnostic chart.

1. If Code P0325 is detected, PCM will retard spark timing. If an audible knock is heard from engine, repair internal engine problem. Normally no knock should be detected at idle.
2. PCM applies 5 volts through a pull-up resistor which should be present at both knock sensor terminals.
3. Determines if knock sensor is faulty or if knock sensor portion of PROM is faulty.
4. Check knock sensor circuit for an intermittent open or short to ground. Also check for proper PROM installation.

Code P0325 Schematic (3.8L) Knock Sensor Error (Dual Sensors). Scheme 30

Code P0325 Diagnostic Flow Chart (3.8L) Knock Sensor Error (Dual Sensors). Scheme 31

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0341 exist.
2. If 5 volts are not present at PCM harness connector terminal cam signal circuit, camshaft position senor may be interfacing with magnet in camshaft sprocket. Bumping starter should correct this condition.
3. If a failure is induced in fuel control reference circuit, 5 volts on circuit should change when faulty wiring or connection is manipulated.

Code P0341 Diagnostic Flow Chart (3.8L) Cam/Crank Error. Scheme 32

Note. Test numbers refer to numbers on diagnostic chart.

1. This step verifies integrity of sensor circuits.
2. This step verifies integrity of circuit between ICM and PCM.
3. Voltage reading will be zero if camshaft gear magnet is interfacing with camshaft position sensor.
4. If voltage reading of cam signal circuit is constantly varying and connection to PCM is good, PCM is faulty.

Code P0342 Diagnostic Flow Chart (3.8L) Cam Signal Circuit. Scheme 33

Note. Test numbers refer to numbers on diagnostic chart.

1. Ensures EGR valve is allowing EGR flow and PCM is capable of controlling EGR valve.
2. Ensures control circuit is not shorted to ground.
3. Ensures control circuit is not open and that PCM quad-driver for circuit is properly functioning.

Code P0401 Schematic (3.8L) (EGR) Flow Test Failure. Scheme 34

Code P0401 Diagnostic Flow Chart (3.8L) (EGR) Flow Test Failure. Scheme 35

Note. Test numbers refer to numbers on diagnostic chart.

1. VSS signal generator only produces a signal if drive wheels are turning greater than 3 MPH.
2. Check PROM for correct application before replacing PCM.

Codes P0501/P0502 Schematic (3.8L) VSS Circuit. Scheme 36

Codes P0501/P0502 Diagnostic Flow Chart (3.8L) VSS Circuit. Scheme 37

Note. Test numbers refer to numbers on diagnostic chart.

1. & 2) Checks for proper operation of transmission range switch.
2. This test checks for an open or grounded circuit. When Code P0705 is present, PCM assumes drive-4 position until a correct combination is received by PCM. Some gear select positions may not be possible until fault is repaired.

Code P0705 Schematic (3.8L) Transaxle Range Switch. Scheme 38

Code P0705 Diagnostic Flow Chart (3.8L) Transaxle Range Switch. Scheme 39

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0712 exist.
2. Simulates conditions to set Code P0713. If PCM recognizes low signal voltage and sets Code P0713, wiring and PCM are okay.
3. Determines if transaxle fluid temperature sensor signal circuit is open. There should be 5 volts present at sensor connector.

Code P0712 Diagnostic Flow Chart (3.8L) Transaxle Temperature Sensor Low Temperature Indicated. Scheme 40

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0713 exist.
2. This test determines if input circuit is shorted to ground which will cause conditions necessary for Code P0713.

Code P0713 Diagnostic Flow Chart (3.8L) Transaxle Temperature Sensor High Temperature Indicated. Scheme 41

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines whether fault is caused by a bad solenoid or control circuit.
2. Checks availability of battery voltage.
3. Checks PCM's ability to pulse PWM solenoid on and off.

Code P0740 Diagnostic Flow Chart (3.8L) Torque Converter Clutch. Scheme 42

Note. Test numbers refer to numbers on diagnostic chart.

1. Ensures no faults exist in injector control and ignition feed wiring.
2. Checks for open or grounded injector feed circuit.
3. Checks for grounded injector drive circuit.
4. Checks for an open injector drive circuit.

Code P1200 Diagnostic Flow Chart (3.8L) Injector Circuit Fault. Scheme 43

Note. Test numbers refer to numbers on diagnostic chart.

1. Circuit shorted to ground will keep by-pass valve closed when PCM is commanding it open, possibly causing an overboost condition during high engine load situations.
2. No inlet vacuum to by-pass valve actuator may cause by-pass valve to remain closed during deceleration. This condition may be perceived as a sail-on, possibly accompanied by a rough idle.

Code P1257 Schematic (3.8L (VIN 1)) Boost Control Problem. Scheme 44

Code P1257 Diagnostic Flow Chart (3.8L (VIN 1)) Boost Control Problem. Scheme 45

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks if PCM recognizes a problem. If Codes P1350/P1361 are not set, problem is intermittent and could be caused by a loose connection.
2. With PCM disconnected, ohmmeter reading should be less than 2000 ohms, which is normal resistance of IC circuit through ICM. A higher resistance indicates a fault in IC circuit, a poor ignition module connection, or a faulty ICM.
3. If test light lights when connected between 12 volts and PCM by-pass circuit terminal, then either by-pass circuit is shorted to ground, or ICM is faulty.
4. Checks if ICM switches when by-pass circuit is energized by 12 volts through test light. If ICM switches, ohmmeter reading should shift to greater than 6000 ohms.
5. Disconnecting ICM should make ohmmeter read as if an open circuit was being monitored (infinite reading). Otherwise, IC circuit is shorted to ground.

Codes P1350/P1361 Schematic (3.8L) IC Circuit. Scheme 46

Codes P1350/P1361 Diagnostic Flow Chart (3.8L) IC Circuit. Scheme 47

Note. Test numbers refer to numbers on diagnostic flow chart (1 Of 2). see scheme 60: Code P1406 Schematic (3.8L) EGR Valve Pintle Position see scheme 61: Code P1406 Diagnostic Flow Chart - 1 Of 2 (3.8L) EGR Valve Pintle Position

1. Checks for an EGR valve sticking partially open or an incorrect pintle position sensor feedback signal.
2. Ensures PCM is capable of controlling EGR pintle position and is reading pintle position feedback signal properly.
3. Checks EGR valve driver in circuit and PCM.

Note. Test numbers refer to numbers on diagnostic chart (2 Of 2).

Code P1406 Diagnostic Flow Chart - 2 Of 2 (3.8L) EGR Valve Pintle Position. Scheme 48

1. Checks will diagnose an incorrect EGR pintle position sensor input signal. This test verifies a 5-volt reference at EGR valve.
2. Ensures position signal circuit is not shorted to ground.
3. Checks position signal circuit for an open.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks for closed switch in Park.
2. Checks for on open switch in Drive.
3. Ensure scan tester does not indicate P/N "actual" as yes even when wiggling shifter. This tests for an intermittent or misadjusted switch.

Code P1520 Schematic (3.8L) Park/Neutral Switch. Scheme 49

Code P1520 Diagnostic Flow Chart (3.8L) Park/Neutral Switch. Scheme 50

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks servo position sensor. If signal is not being received at PCM, use Code P1565 to diagnose problem.
2. Verifies vacuum portion of cruise system is operational.
3. Checks for faulty brake switch.

Code P1558 Schematic (3.8L) Cruise System Problem SPS Indicated Low. Scheme 51

Code P1558 Diagnostic Flow Chart (3.8L) Cruise System Problem SPS Indicated Low. Scheme 52

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks circuit for an open or short to ground.
2. Ensures EBTCM is proving a proper PWM signal to PCM.

Code P1571 Schematic (3.8L) Traction Control Desired Torque Out Of Range. Scheme 53

Code P1571 Diagnostic Flow Chart (3.8L) Traction Control Desired Torque Out Of Range. Scheme 54

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks if EBTCM is able to transmit data and ensures serial data circuit to EBTCM is not open.

Code P1573 Diagnostic Flow Chart (3.8L) Traction Control Fault Loss Of ABS/TCS Serial Data. Scheme 55

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks circuit for a short to ground.
2. Checks for a faulty PCM or an intermittent condition.

Code P1619 Schematic (3.8L) Engine Oil Life Monitor Reset Circuit. Scheme 56

Code P1619 Diagnostic Flow Chart (3.8L) Engine Oil Life Monitor Reset Circuit. Scheme 57

Note. Test numbers refer to numbers on diagnostic chart.

1. If vehicle does not crank with Code P1626 or P1629 stored, problem affects entire theft deterrent system and is not isolated to fuel enable circuit.
2. PCM supplies 5 volts to fuel enable input circuit which theft deterrent module pulses to ground when correct key resistance is recognized. This test ensures PCM is supplying 5 volts and circuit is not open or shorted to ground.
3. Checks signal from theft deterrent module. DC frequency on circuit should measure approximately 50 hertz.
4. Checks for a faulty PCM or intermittent condition by clearing Code P1626 or P1629. Since PCM ignores absence of a fuel enable signal only when Code P1626 or P1629 is stored, vehicle should not start if problem is present and Code P1626 or P1629 has been cleared.

Codes P1626/1629 Schematic (3.8L) Pass-Key II Fuel Enable Circuit. Scheme 58

Codes P1626/1629 Diagnostic Flow Chart (3.8L) Pass-Key II Fuel Enable Circuit. Scheme 59

Note. Test numbers refer to numbers on diagnostic chart.

1. Test generator output to determine proper operation of voltage regulator. Run engine at moderate speed and measure voltage across battery. If reading is less than 9 volts or greater than 17.3 volts, repair generator.

Code P1630 Schematic (3.8L) System Voltage High/Low. Scheme 60

Code P1630 Diagnostic Flow Chart (3.8L) System Voltage High/Low. Scheme 61

Note. Test numbers refer to numbers on diagnostic chart.

1. If QDM related code is stored, diagnose that code first. Repair made to related code will repair Code P1640 also.
2. If QDM No. 1 symptoms are present, checks on Code P1640 (2 Of 2) chart should isolate cause of fault.
3. This test will determine which circuit is out of specification.
4. Determines if problem is circuit or component.
5. As factory installed PCM is protected with an internal circuit breaker, it is highly unlikely that PCM needs to be replaced.

Code P1640 Schematic (3.8L) QDM No. 1 Circuit. Scheme 62

Code P1640 Diagnostic Flow Chart (3.8L) QDM No. 1 Circuit. Scheme 63

Note. Test numbers refer to numbers on diagnostic chart.

1. If QDM related code is stored, diagnose that code first. Repair made to related code will repair Code P1650 also.
2. This test will determine which circuit is out of specification.
3. Determines if problem is circuit or component.
4. As factory installed PCM is protected with an internal circuit breaker, it is highly unlikely that PCM needs to be replaced.

Code P1650 Schematic (3.8L) QDM No. 2. Scheme 64

Code P1650 Diagnostic Flow Chart (3.8L) QDM No. 2. Scheme 65

Note. Test numbers refer to numbers on diagnostic chart.

1. If QDM No. 4 related symptoms are present, checks on Code P1670 (2 OF 2) chart should isolate cause of fault.
2. Determines which circuit is out of specification.
3. Determines if problem is circuit or component.
4. As factory installed PCM is protected with an internal circuit breaker, it is highly unlikely that PCM needs to be replaced.

Code P1670 Schematic (3.8L) QDM No. 4. Scheme 66

Code P1670 Diagnostic Flow Chart (3.8L) QDM No. 4. Scheme 67

Note. Test numbers refer to numbers on diagnostic chart.

1. Ensures PCM is capable of controlling solenoid.
2. Checks TCC PWM driver circuit for short to ground.

Code 1860 Schematic (3.8L) TCC PWM Solenoid. Scheme 68

Code 1860 Diagnostic Flow Chart (3.8L) TCC PWM Solenoid. Scheme 69