Engine Control System - 3.6l (ly7) - DTC p0135 to DTC p0430 Buick LaCrosse I

Circuit Description

The heated oxygen sensor (HO2S) heater reduces the time required for the oxygen sensor (O2S) to reach operating temperature and maintains the operating temperature during extended idle periods. When the ignition is turned to the ON position, ignition voltage is supplied directly to the sensor heater. The engine control module (ECM) controls the heater operation by first modulating the control circuit to ground when the sensors are cold. This prevents the possibility of thermal shock to the sensor, from condensation build-up on the sensor, by controlling the sensors rate of heating. After a predetermined amount of time, the ECM commands the heaters ON continuously. Once the sensor reaches operating temperature, the ECM may modulate the heater control circuit to ground, to maintain a desired temperature.

The ECM measures the HO2S sensing cell internal resistance. If the ECM detects that the HO2S sensing cell internal resistance is too high, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC P0135 HO2S Heater Performance Sensor 1

Condition 1

1. Before the ECM can report DTC P0135 failed, DTCs P0030, P0031, P0032, P0101, P0102, P0103, P0121, P0122, P0123, P0130, P0131, P0132, P0221, P0222, P0223, P0335, P0336, P0338, P167A, P2237, P2243 and P2251 must run and pass.
2. The ignition 1 voltage is between 10.5-18 volts.
3. The HO2S is at operating temperature for more than 50 seconds.
4. The time after decel fuel cut-off is more than 53 seconds.
5. The HO2S heater is commanded ON to 100 percent.
6. The calculated exhaust temperature is more than 550°C (1,022°F).
7. The ECM internal sensing element resistance test is enabled.
8. DTC P0135 runs continuously once the above conditions are met for 1 minute.

Condition 2

1. Before the ECM can report DTC P0135 failed, DTCs P0030, P0031, P0032, P0101, P0102, P0103, P0121, P0122, P0123, P0130, P0131, P0132, P0221, P0222, P0223, P0335, P0336, P0338, P167A, P2237, P2243 and P2251 must run and pass.
2. The ignition 1 voltage is between 10.5-18 volts.
3. The ECT is more than -10°C (+14°F) at start up.
4. The HO2S is at operating temperature.
5. The ECM internal sensing element resistance test is enabled.
6. The fuel injectors are not disabled.
7. If the engine is operating and then the ignition is turned OFF, the engine must be OFF for at least 5 minutes before the next start-up for the diagnostic to run.
8. DTC P0135 runs continuously once the above conditions are met for more than 2 minutes.

1. The ECM has determined that the HO2S internal sensing element resistance is less than a predetermined threshold.
2. The condition exists for more than 4 seconds.

1. The ECM detects that the calculated HO2S temperature is less than 600°C (1,112°F).
2. The condition exists for more than 4 seconds.

Action Taken When the DTC Sets

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

The following table illustrates the ECM connector locations

DTC P0135

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The front wide band sensors do not toggle or switch like a switching HO2S. The front HO2S signals will be relatively stable for an idling engine.
3. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .
4. The following table illustrates the typical voltages for the HO2S circuits

HO2S Voltages

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if the condition exists. If there is an HO2S circuit condition, the ECM commands open loop for the applicable sensor.
2. 4: This step tests for a bias voltage across the reference voltage circuit and the low reference circuit of the HO2S. The bias voltage that you are measuring, is the voltage difference between the reference voltage circuit and the low reference circuit. If there is a condition with the reference voltage circuit or the low reference circuit of the HO2S, the bias voltage will be more than or less than the specified value.
3. 5: This step tests the ignition 1 voltage circuit of the HO2S for high resistance. If the voltage at the test lamp probe is not B+, there is a high resistance condition with the circuit.
4. 10: This step inspects the harness connector for water intrusion, corrosion and bent or damaged pins.
5. 11: This step inspects the harness connector for water intrusion, corrosion and bent or damaged pins.

DTC P0135

The engine control module (ECM) supplies a voltage near 450 mV between the heated oxygen sensor (HO2S) high signal circuit and the low reference circuit. The HO2S varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.

The ECM monitors and stores the HO2S voltage information. The ECM evaluates the HO2S voltage samples in order to determine the amount of time that the HO2S voltage was out of range. The ECM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range.

The ECM monitors the HO2S voltage for being fixed below a predetermined voltage. If the ECM detects the voltage is too low, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0137 HO2S Circuit Low Voltage Sensor 2

Conditions for Running the DTC

1. DTCs P0117, P0118, P0125 and P0128 are not set.
2. The engine is operating for more than 1 second.
3. The HO2S heater is at operating temperature for more than 10 seconds.
4. The ignition 1 voltage is more than 10.5 volts.
5. The engine coolant temperature (ECT) is less than 40°C (104°F) at start-up and the ECT was more than 60°C (140°F) when the ignition was turned OFF last ignition cycle.
6. The calculated exhaust temperature is between 250-800°C (482-1,472°F).
7. DTC P0137 runs continuously once the above conditions are met for more than 90 seconds.

Conditions for Setting the DTC

1. The ECM detects that the HO2S signal voltage is less than 60 mV.
2. The condition exists for less than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0137

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The rear HO2S will not go into closed loop when the engine is idling. Once the HO2S are at operating temperature and the vehicle is moving, the rear HO2S will go into closed loop.
3. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

DTC P0137

The engine control module (ECM) supplies a voltage near 450 mV between the heated oxygen sensor (HO2S) high signal circuit and the low reference circuit. The HO2S varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.

The ECM monitors and stores the HO2S voltage information. The ECM evaluates the HO2S voltage samples in order to determine the amount of time that the HO2S voltage was out of range. The ECM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range.

The ECM monitors the HO2S voltage for being fixed above a predetermined voltage. If the ECM detects the voltage is too high, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0138 HO2S Circuit High Voltage Sensor 2

1. The engine is operating.
2. The ignition 1 voltage is more than 10.5 volts.
3. The HO2S heater is at operating temperature for more than 10 seconds.
4. The calculated exhaust temperature is between 250-800°C (482-1,472°F).
5. DTC P0138 runs continuously once the above conditions are met for more than 90 seconds.

1. The ECM detects that the HO2S signal voltage is more than 1,050 mV.
2. The condition exists for more than 5.1 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0138

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The rear HO2S will not go into closed loop when the engine is idling. Once the HO2S is at operating temperature and the vehicle is moving, the rear HO2S will go into closed loop.
3. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if the condition exists. If there is an HO2S circuit condition, the HO2S voltage will be more than the specified value.
2. 4: This step isolates the condition. If the voltage is more than the specified with the engine OFF, this indicates there is a circuit condition.
3. 5: This step isolates if the condition is with the signal circuit or the low reference circuit of the HO2S. If the signal circuit voltage is within the specified range, the low reference circuit is short to a voltage.
4. 8: This step test for a fuel system that is operating rich.
5. 9: This step inspects the harness connector for water intrusion. Moisture in a connector may cause voltage to bleed to other circuits.
6. 10: This step inspects the harness connector for water intrusion. Moisture in a connector may cause voltage to bleed to other circuits.

DTC P0138

The engine control module (ECM) supplies a voltage near 450 mV between the heated oxygen sensor (HO2S) high signal circuit and the low reference circuit. The HO2S varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.

The ECM monitors and stores the HO2S voltage information. The ECM evaluates the HO2S voltage samples in order to determine the amount of time that the HO2S voltage was out of range. The ECM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range.

The ECM monitors the HO2S voltage and detects if the voltage goes out of the bias range. If the ECM does not detect the voltage went out of the bias range, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0140 HO2S Circuit Insufficient Activity Sensor 2

1. The engine is operating.
2. The HO2S heater is at operating temperature for more than 10 seconds.
3. The ignition 1 voltage is more than 10.5 volts.
4. The calculated exhaust temperature is between 250-800°C (482-1,472°F).
5. DTC P0140 runs continuously once the above conditions are met for more than 90 seconds.

The ECM detects that the HO2S voltage is between 400-520 mV for more than 10 minutes.

OR

The ECM detects that the measured internal resistance of the HO2S is more than 40,000 ohms, when the calculated exhaust temperature is more than 600°C (1,112°F).

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0140

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The rear HO2S will not go into Closed Loop when the engine is idling. Once the HO2S are at operating temperature and the vehicle is moving, the rear HO2S will go into Closed Loop.
3. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if the condition exists. The HO2S voltage parameter should react immediately to the changes in throttle position when performing this test.
2. 4: This step tests the HO2S signal circuit for an open. If a bias voltage is not available, there is a condition with the circuit.
3. 5: This step tests the HO2S low reference circuit for an open. If the HO2S voltage does not go below the specified value, there is a condition with the circuit.

DTC P0140

The heated oxygen sensor (HO2S) heater reduces the time required for the oxygen sensor (O2S) to reach operating temperature and maintains the operating temperature during extended idle periods. When the ignition is turned to the ON position, ignition voltage is supplied directly to the sensor heater. The engine control module (ECM) controls the heater operation by first modulating the control circuit to ground when the sensors are cold. This prevents the possibility of thermal shock to the sensor, from condensation build-up on the sensor, by controlling the sensors rate of heating. After a predetermined amount of time, the ECM commands the heaters ON continuously. Once the sensor reaches operating temperature, the ECM may modulate the heater control circuit to ground, to maintain a desired temperature.

The ECM controls the heater by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to voltage. The ECM can determine if the control circuit is open, shorted to ground or shorted to a voltage by monitoring the feedback voltage.

The ECM calculates the HO2S heater element resistance based on the internal HO2S sensing element. If the ECM detects that the HO2S heater element resistance is too high, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0141 HO2S Heater Performance Sensor 2

1. Before the ECM can report DTC P0141 failed, DTCs P0036, P0037 and P0038 must run and pass.
2. DTCs P0137, P0138, P0140, P2232, P2270 and P2271 are not set.
3. The engine is operating.
4. The ignition 1 voltage is between 10.5-18 volts.
5. The ECM internal sensing element resistance test is enabled.
6. The fuel system is not in a decel fuel shut-off.
7. The intake air temperature (IAT) is more than -7°C (20°F).
8. If the engine is operating and then the ignition is turned OFF, the engine must be OFF for at least 2 minutes before the next start-up for the diagnostic to run.
9. The calculated exhaust temperature is between 360-500°C (680-932°F).
10. DTC P0141 runs continuously once the above conditions are met for more than 100 seconds.

1. The ECM detects that the HO2S internal resistance is not within the expected range.
2. The condition exists for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0141

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The rear HO2S will not go into closed loop when the engine is idling. Once the HO2S are at operating temperature and the vehicle is moving, the rear HO2S will go into closed loop.
3. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if the condition exists.
2. 4: This step tests the signal circuit of the HO2S for high resistance.

DTC P0141

The control module enables the appropriate fuel injector on the intake stroke for each cylinder. Ignition voltage is supplied directly to the fuel injectors. The control module controls each fuel injector by grounding the control circuit with a solid state device called a driver. The control module monitors the status of each driver. Each driver has a feedback voltage circuit which the engine control module (ECM) monitors. The injector control circuits are pulled-up to voltage within the ECM. The ECM can determine if a control circuit is open, shorted to ground or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is between a predetermined range when the circuit is commanded OFF, this DTC sets.

DTC Descriptors

This diagnostic procedure supports the following DTCs

1. DTC P0201 Injector 1 Control Circuit
2. DTC P0202 Injector 2 Control Circuit
3. DTC P0203 Injector 3 Control Circuit
4. DTC P0204 Injector 4 Control Circuit
5. DTC P0205 Injector 5 Control Circuit
6. DTC P0206 Injector 6 Control Circuit

1. The engine speed is more than 80 RPM.
2. The ignition 1 voltage is between 10-18 volts.
3. DTC P0201-P0206 runs continuously once the above conditions are met.

1. The ECM detects an open in the fuel injector circuits.
2. The condition exists for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0201-P0206

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. Performing the fuel injector coil test may help isolate an intermittent condition. Refer to «Fuel Injector Coil Test»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting) .
3. If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the circuit status for the component with a scan tool. The circuit status parameter changes from OK or Indeterminate to Fault if there is a condition with the circuit or a connection. The ODM information is in the output driver module (ODM) data list.
4. If the condition is intermittent, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step verifies that the condition is present.
2. 3: This step determines if there is condition with the ignition 1 voltage supply circuit. The fuel injectors for each bank of the engine are fused separately. If all the fuel injector open DTCs set for one bank of the engine, there is a condition with one of the ignition 1 voltage supply circuits.
3. 5: This step verifies that the ECM is able to control the fuel injector.
4. 6: This step tests if the feedback voltage circuit within the ECM is providing the correct voltage. This feedback voltage is used for determining if the fuel injector control circuit is open, shorted to a ground or shorted to a voltage.

DTC P0201-P0206

The throttle body assembly contains 2 throttle position (TP) sensors. The TP sensors are mounted to the throttle body assembly and are not serviceable. The TP sensors provide a signal voltage that changes relative to throttle blade angle. The engine control module (ECM) supplies the TP sensors with a common 5-volt reference circuit, a common low reference circuit and 2 independent signal circuits.

The TP sensors have opposite functionality. TP sensor 1 signal voltage increases from below 1 volt at idle to above 4 volts at wide open throttle. TP sensor 2 signal voltage decreases from above 4 volts at idle to below 1 volt at wide open throttle.

The ECM compares the signal of the TP sensor 1 and TP sensor 2 through the entire range. If the ECM detects a predetermined difference between sensor 1 and sensor 2 or a predetermined difference from the predicted range, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0221 Throttle Position (TP) Sensor 2 Performance

1. The ignition 1 voltage is more than 7 volts.
2. The TP 2 voltage is between 0.15-4.8 volts.
3. DTC P0221 runs continuously once the above conditions are met.

1. The TP sensor 1 disagrees more than 9 percent from TP sensor 2.
2. The TP sensor 2 disagrees more than 9 percent from the predicted value.
3. The above conditions are met for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0221

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. If there is a condition with the TP sensors the ECM defaults to reduced power mode for the entire ignition cycle, even if the condition is corrected and the DTC is cleared.
3. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step verifies that a condition exists. If there is a condition with a TP sensor circuit, the scan tool displays, Disagree.
2. 5: This step tests for high resistance in the 5-volt reference circuit of the TP sensors. If the DMM does not display more than the specified voltage there is high resistance in the circuit.
3. 8: This step tests for high resistance in the low reference circuit of the TP sensor. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM fuse or the PCM/ETC fuse, allows the ECM to power down completely.

DTC P0221

The throttle body assembly contains 2 throttle position (TP) sensors. The TP sensors are mounted to the throttle body assembly and are not serviceable. The TP sensors provide a signal voltage that changes relative to throttle blade angle. The engine control module (ECM) supplies the TP sensors with a common 5-volt reference circuit, a common low reference circuit and 2 independent signal circuits.

The TP sensors have opposite functionality. TP sensor 1 signal voltage increases from below 1 volt at idle to above 4 volts at wide open throttle. TP sensor 2 signal voltage decreases from above 4 volts at idle to below 1 volt at wide open throttle.

If the ECM detects TP sensor 2 signal voltage is too low, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0222 Throttle Position (TP) Sensor 2 Circuit Low Voltage

1. The ignition is ON, with the engine OFF or the engine is operating.
2. The ignition 1 voltage is more than 7 volts.
3. DTC P0222 runs continuously once the above conditions are met.

The ECM detects the TP sensor 2 signal voltage is less than 0.16 volts for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0222

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. If there is a condition with the TP sensors the ECM defaults to reduced power mode for the entire ignition cycle, even if the condition is corrected.
3. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step verifies that a condition exists.
2. 4: The TP sensors share a 5-volt reference circuit. If both DTCs P0122 and P0222 set, test for a condition in the 5-volt reference circuit.
3. 5: This step tests for a condition in the 5-volt reference circuit of the TP sensor. If the DMM displays less 4.8 volts test for a high resistance, an open or a short to ground in the circuit.
4. 6: This step tests the signal 2 circuit of the TP sensor. If the TP sensor 2 voltage parameter is not 4.8-5.2 volts, test for a condition in the signal 2 circuit.

DTC P0222

The throttle body assembly contains 2 throttle position (TP) sensors. The TP sensors are mounted to the throttle body assembly and are not serviceable. The TP sensors provide a signal voltage that changes relative to throttle blade angle. The engine control module (ECM) supplies the TP sensors with a common 5-volt reference circuit, a common low reference circuit and 2 independent signal circuits.

The TP sensors have opposite functionality. TP sensor 1 signal voltage increases from below 1 volt at idle to above 4 volts at wide open throttle. TP sensor 2 signal voltage decreases from above 4 volts at idle to below 1 volt at wide open throttle.

If the ECM detects TP sensor 2 signal voltage is too high, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0223 Throttle Position (TP) Sensor 2 Circuit High Voltage

1. The ignition is ON, with the engine OFF or the engine is operating.
2. The ignition 1 voltage is more than 7 volts.
3. DTC P0223 runs continuously once the above conditions are met.

The ECM detects the TP sensor 2 signal voltage is more than 4.8 volts for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0223

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. If there is a condition with the TP sensors the ECM defaults to reduced power mode for the entire ignition cycle, even if the condition is corrected.
3. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if a condition exists.
2. 4: This step tests the signal circuit for a short to voltage. If the scan tool displays a voltage after the TP sensor is disconnected, the circuit is shorted to a voltage.
3. 6: This step tests for high resistance in the low reference circuit of the TP sensor. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM fuse or the PCM/ETC fuse, allows the ECM to power down completely.
4. 7: This step tests the low reference circuit for a short to voltage.

DTC P0223

The control module enables the appropriate fuel injector on the intake stroke for each cylinder. Ignition voltage is supplied directly to the fuel injectors. The control module controls each fuel injector by grounding the control circuit with a solid state device called a driver. The control module monitors the status of each driver. Each driver has a feedback voltage circuit which the engine control module (ECM) monitors. The injector control circuits are pulled-up to voltage within the ECM. The ECM can determine if a control circuit is open, shorted to ground or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is too low when the circuit is commanded OFF, this DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P0261 Injector 1 Control Circuit Low Voltage
2. DTC P0264 Injector 2 Control Circuit Low Voltage
3. DTC P0267 Injector 3 Control Circuit Low Voltage
4. DTC P0270 Injector 4 Control Circuit Low Voltage
5. DTC P0273 Injector 5 Control Circuit Low Voltage
6. DTC P0276 Injector 6 Control Circuit Low Voltage

1. The engine speed is more than 80 RPM.
2. The ignition 1 voltage is between 10-18 volts.
3. DTCs P0261, P0264, P0267, P0270, P0273 and P0276 run continuously once the above conditions are met.

1. The ECM detects a grounded fuel injector circuit.
2. The condition exists for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0261, P0264, P0267, P0270, P0273 or P0276

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. Performing the fuel injector coil test may help isolate an intermittent condition. Refer to «Fuel Injector Coil Test»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting) .
3. If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the circuit status for the component with a scan tool. The circuit status parameter changes from OK or Indeterminate to Fault if there is a condition with the circuit or a connection. The ODM information is in the output driver module (ODM) data list.
4. If the condition is intermittent, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if the condition is current.
2. 3: This step determines if the ignition 1 voltage supply circuit is shorted to ground. The fuel injectors for each bank of the engine are fused separately. If the circuit is shorted to ground, all the injector low voltage DTCs will set for one bank of the engine.
3. 5: This step isolates if the short to ground condition is on the injector side of the multi-way harness connector or the ECM side of the multi-way harness connector. If a low voltage DTC sets, the short to ground condition is between the multi-way harness connector and the ECM.
4. 7: This step isolates the condition. If the test lamp illuminates the injector control circuit is shorted to ground between the multi-way harness connector and the fuel injectors.

DTC P0261, P0264, P0267, P0270, P0273 or P0276

The control module enables the appropriate fuel injector on the intake stroke for each cylinder. Ignition voltage is supplied directly to the fuel injectors. The control module controls each fuel injector by grounding the control circuit with a solid state device called a driver. The control module monitors the status of each driver. Each driver has a feedback voltage circuit which the engine control module (ECM) monitors. The injector control circuits are pulled-up to a voltage within the ECM. The ECM can determine if a control circuit is open, shorted to ground or shorted to a voltage by monitoring the feedback voltage. If the ECM detects the control circuit voltage is too high when the circuit is commanded ON, this DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P0262 Injector 1 Control Circuit High Voltage
2. DTC P0265 Injector 2 Control Circuit High Voltage
3. DTC P0268 Injector 3 Control Circuit High Voltage
4. DTC P0271 Injector 4 Control Circuit High Voltage
5. DTC P0274 Injector 5 Control Circuit High Voltage
6. DTC P0277 Injector 6 Control Circuit High Voltage

1. The engine speed is more than 80 RPM.
2. The ignition 1 voltage is between 10-18 volts.
3. DTCs P0262, P0265, P0268, P0271, P0274 and P0277 run continuously once the above conditions are met.

1. The ECM detects a short to voltage on the fuel injector circuits.
2. The condition exists for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0262, P0265, P0268, P0271, P0274 or P0277

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. Performing the fuel injector coil test may help isolate an intermittent condition. Refer to «Fuel Injector Coil Test»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting) .
3. If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the circuit status for the component with a scan tool. The circuit status parameter changes from OK or Indeterminate to Fault if there is a condition with the circuit or a connection. The ODM information is in the output driver module (ODM) data list.
4. If the condition is intermittent, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if the condition is current.
2. 4: This step tests for a short to voltage on the fuel injector control circuit. If the voltage is more than the specified value, the circuit is shorted to a voltage or there is an internal ECM condition.
3. 6: This step tests if the ignition 1 voltage supply circuit is shorted to the fuel injector control circuit.

DTC P0262, P0265, P0268, P0271, P0274 or P0277

Description

The engine control module (ECM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensors in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM is able to detect individual misfire events. A misfire rate that is high enough can cause 3-way catalytic converter (TWC) damage. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for catalytic converter damage are present. DTCs P0301 through P0306 correspond to cylinders 1 through 6. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder will set. If the misfire rate is sufficient to cause emission levels to exceed a predetermined value, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0300 Engine Misfire Detected

1. DTCs P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336 and P0338 are not set.
2. The engine speed is between 400-7,000 RPM and steady.
3. The delivered torque signal is more than 10 percent at idle.
4. The delivered torque signal is between 9-30 percent with the transmission in drive.
5. The intake air temperature (IAT) is more than -30°C (-22°F).
6. The fuel level is more than 12 percent.
7. The torque management is not active.
8. The antilock brake system (ABS)/traction control system (TCS) is not active.
9. The ECM is not receiving a rough road signal.
10. The fuel cut-off is not active, including the traction control, the deceleration, the high vehicle speed and the high engine speed.
11. DTC P0300 runs continuously when the above conditions exist for at least 1000 engine revolutions.

1. The ECM detects a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed mandated standards.
2. The condition above exists for more than 4 seconds.

1. The control module illuminates the MIL on the second ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail within similar conditions.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. A misfire DTC could be caused by an excessive vibration from sources other than the engine. Inspect for the following possible sources: A tire or wheel that is out of round or out of balance Variable thickness brake rotors An unbalanced drive shaft Certain rough road conditions A damaged accessory drive component or belt
2. A misfire DTC could be caused by a camshaft actuator stuck in the full advance or retard position.
3. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if there is a current condition.
2. 4: If the Misfire Current Counters are incrementing, but the engine is NOT misfiring, this indicates a mechanical condition. For example, an accessory drive belt could cause this condition.

DTC P0300 - Engine Misfire Detected

The engine control module (ECM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensors in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM is able to detect individual misfire events. A misfire rate that is high enough can cause 3-way catalytic converter (TWC) damage. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for catalytic converter damage are preset. DTCs P0301-P0306 correspond to cylinders 1-6. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder sets.

This diagnostic procedure supports the following DTCs

1. DTC P0301 Cylinder 1 Misfire Detected
2. DTC P0302 Cylinder 2 Misfire Detected
3. DTC P0303 Cylinder 3 Misfire Detected
4. DTC P0304 Cylinder 4 Misfire Detected
5. DTC P0305 Cylinder 5 Misfire Detected
6. DTC P0306 Cylinder 6 Misfire Detected

1. DTCs P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336 and P0338 are not set.
2. The engine speed is between 400-7,000 RPM and steady.
3. The delivered torque signal is more than 10 percent at idle.
4. The delivered torque signal is between 9-30 percent with the transmission in drive.
5. The intake air temperature (IAT) is more than -30°C (-22°F).
6. The fuel level is more than 12 percent.
7. The torque management is not active.
8. The antilock brake system (ABS)/traction control system (TCS) is not active.
9. The ECM is not receiving a rough road signal.
10. The fuel cut-off is not active, including the traction control, the deceleration, the high vehicle speed and the high engine speed.
11. DTCs P0301 - P0306 run continuously when the above conditions exist for at least 1000 engine revolutions.

1. The ECM detects a crankshaft rotation speed variation indicating a single cylinder misfire rate sufficient to cause emissions levels to exceed mandated standard.
2. The condition above exists for more than 4 seconds.

1. The control module illuminates the MIL on the second ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail within similar conditions.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. A misfire DTC could be caused by an excessive vibration from sources other than the engine. Inspect for the following possible sources: A tire or wheel that is out of round or out of balance Variable thickness brake rotors An unbalanced drive shaft Certain rough road conditions A damaged accessory drive component or belt
2. A misfire DTC could be caused by a camshaft actuator stuck in the full advance or retard position.
3. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

DTC P0301 - P0306 Cylinder Misfire Detected

Correct engine misfire detection is dependent on whether or not the vehicle is experiencing a rough road condition. A rough road condition causes unexpected crankshaft fluctuations. In order to detect a rough road condition, the electronic brake control module (EBCM) communicates a wheel speed signal over the serial data circuit to the engine control module (ECM). The wheel speed sensor information allows the ECM to distinguish if the crankshaft speed variations are caused by a rough road condition or are caused by a true misfire. If the EBCM reports a wheel speed sensor failure or the ECM does not receive the rough road information, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0318 Rough Road Sensor Circuit

1. The ignition is ON or the engine is operating.
2. DTC P0318 runs continuously once the above conditions are met.

1. The EBCM reports a wheel speed sensor failure to the ECM. OR
2. The ECM does not receive communication of a rough road signal from the EBCM for more than 5 seconds.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

1. A condition with a wheel speed sensor will cause this DTC to set.
2. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: A condition with the wheel speed sensors or the serial data circuits between the EBCM and ECM can cause this DTC.

DTC P0318

The knock sensor (KS) system monitors the KS in order to determine if detonation is present. If the KS system determines that excessive knock is present, the engine control module (ECM) retards the spark timing based on the signal from the KS system. The KS produces an AC signal when specific frequencies are detected. The ECM then retards the timing until no knock is present.

The ECM tests the functionality of the internal KS signal evaluation circuitry. The KS circuitry within the ECM is responsible for receiving, amplifying, filtering and evaluating the AC voltage and frequency from the KS. The ECM performs 2 tests that determine if the internal circuitry within the ECM is functioning correctly.

Test One

The ECM internally turns OFF the KS signal circuits. The ECM then applies different test signals to the internal KS circuitry to verify that each test signal output response is within range. If the ECM detects that any of the test signals are not within range, this DTC sets.

Test Two

The ECM internally turns OFF the KS signal circuits. The ECM then tests for any output response when no test signals are applied. If the ECM detects an output response, this DTC sets.

Test Three

The ECM internally turns OFF the KS signal circuits. The ECM generates an internal test pulse and monitors the return signal. If the return test pulse is less than a calibrated threshold, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0324 Knock Sensor (KS) Module Performance

Conditions 1

1. Before the ECM can report DTC P0324 failed, DTC P0335, P0336 and P0338 must run and pass.
2. The ECM is controlling spark.
3. The increase in engine speed is less than 2,300 RPM per second.
4. The volumetric efficiency is steady.
5. DTC P0324 runs continuously every 510 engine revolutions, once the above conditions are met for a total 50 seconds.

Conditions 2

1. Before the ECM can report DTC P0324 failed, DTC P0335, P0336 and P0338 must run and pass.
2. The ECM is controlling spark.
3. The engine speed is between 1,000-4,000 RPM and steady.
4. The volumetric efficiency is steady.
5. DTC P0324 runs continuously every 510 engine revolutions, once the above conditions are met for a total 50 seconds.

Conditions 3

1. Before the ECM can report DTC P0324 failed, DTC P0335, P0336 and P0338 must run and pass.
2. The ECM is controlling spark.
3. The engine coolant temperature is more than 60°C (140°F).
4. The increase in engine speed is less than 2,300 RPM per second.
5. The volumetric efficiency is steady.
6. DTC P0324 runs continuously every 510 engine revolutions, once the above conditions are met for a total 50 seconds.

1. The ECM detects an incorrect response to the self tests performed on the internal KS circuitry.
2. The condition exists for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if a condition exists.
2. 3: A crankshaft sensor DTC could cause this DTC to set.

DTC P0324

The knock sensor (KS) is a piezoelectric device that produces an AC voltage of different amplitude and frequency depending on the level of engine mechanical vibration. The KS system monitors the KS in order to determine if detonation is present. If the KS system determines that excessive knock is present, the engine control module (ECM) retards the spark timing based on the signal from the KS system. The KS produces an AC signal when specific frequencies are detected. The ECM then retards the timing until no knock is present.

In order to differentiate between normal engine noise and spark knock, the ECM samples the KS signal. The ECM samples the KS signal for a certain length of time under different engine speeds and loads during cylinder firing events. This sampling is used to determine a range of acceptable normal engine noise. If the ECM does not detect sufficient normal engine noise from the KS, this DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P0327 Knock Sensor (KS) Circuit Low Voltage Bank 1
2. DTC P0332 Knock Sensor (KS) Circuit Low Voltage Bank 2

1. Before the ECM can report DTC P0327 or P0332 failed, DTCs P0324, P0335, P0336 and P0338, must run and pass.
2. DTCs P0341, P0342, P0343, P0346, P0347, P0348, P0366, P0367, P0368, P0391, P0392 and P0393 are not set.
3. The ECM is controlling spark.
4. The engine coolant temperature (ECT) sensor is more than 60°C (140°F).
5. The engine speed is more than 2,000 RPM and steady.
6. The volumetric efficiency is steady.
7. DTC P0327 and P0332 run continuously once the above conditions are met for approximately 20 seconds.

The ECM detects a KS signal voltage that is less than the typical engine noise level for at least 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0327 or P0332

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The KS must be torqued correctly. Refer «Fastener Tightening Specifications»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction-2-of-2__fastener-tightening-specifications) .
3. The mounting between the sensor and engine must be free of burrs, casting flash and foreign material.
4. The KS is clear from hoses, brackets and engine wiring.
5. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step verifies a condition is present.
2. 4: This step determines if there is a condition with the KS circuit. If the voltage increases when the circuit is grounded, this indicates that there is no condition with the KS circuit. If there is a condition with either circuit, the voltage will not increase when the circuits are connected to ground.

P0327 or P0332 Knock Sensor (KS) Circuit Low Voltage Bank 1 or Bank 2

The knock sensor (KS) is a piezoelectric device that produces an AC voltage of different amplitude and frequency depending on the level of engine mechanical vibration. The KS system monitors the KS in order to determine if detonation or spark knock is present. If the KS system determines that excessive knock is present, the engine control module (ECM) retards the spark timing based on the signal from the KS system. The KS produces an AC signal when specific frequencies are detected. The ECM then retards the timing until no knock is present.

In order to differentiate between normal engine noise and spark knock, the ECM samples the KS signal. The ECM samples the KS signal for a certain length of time under different engine speeds and loads during non-cylinder knock events. This sampling is used to determine a range of acceptable normal engine noise. If the ECM detects too much normal engine noise from a KS, a KS DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P0328 Knock Sensor (KS) Circuit High Voltage Bank 1
2. DTC P0333 Knock Sensor (KS) Circuit High Voltage Bank 2

1. Before the ECM can report DTC P0328 or P0333 failed, DTC P0324, P0335, P0336 and P0338 must run and pass.
2. The engine is operating.
3. The engine speed is more than 2,000 RPM and steady.
4. The ECM is controlling spark.
5. The volumetric efficiency is steady.
6. DTC P0328 and P0333 run continuously once the above conditions are met for approximately 20 seconds.

The ECM detects the KS signal voltage is more than the maximum normal engine noise level for at least 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0328 or P0333

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. The KS must be torqued correctly. Refer «Fastener Tightening Specifications»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction-2-of-2__fastener-tightening-specifications) .
3. The mounting between the sensor and engine must be free of burrs, casting flash and foreign material.
4. The KS is clear from hoses, brackets and engine wiring.
5. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step verifies a condition is present.
2. 4: This step is testing for electromagnetic interference (EMI). If the KS circuits are routed close to high load circuits or components, this DTC may set.
3. 5: This step is testing for a poor connection at the component and for an intermittent condition with the wiring.
4. 6: This step is testing if the KS is installed correctly. A KS that is not fully seated, may cause this DTC to set.

P0328 or P0333 Knock Sensor (KS) Circuit High Voltage Bank 1 or Bank 2

The crankshaft position (CKP) sensor is located on the rear of bank 1 of the engine block. The CKP sensor produces an AC voltage of different amplitude and frequency depending on the velocity of the crankshaft. The CKP sensor works in conjunction with a 58X reluctor wheel that is attached to the crankshaft. Each tooth on the reluctor wheel are spaced 6 degrees apart with one span having a 12-degree space. The engine control module (ECM) uses the 12-degree space to determine top dead center for cylinders 1 and 4. The ECM determines when cylinder 1 is on the compression stroke by monitoring the CKP sensor and the camshaft position (CMP) sensors. The ECM can synchronize the ignition timing, fuel injector timing and spark knock control based on the CKP sensor and the CMP sensor inputs. If the ECM does not detect a signal from the CKP sensor, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0335 Crankshaft Position (CKP) Sensor Circuit

1. The engine is cranking or operating.
2. The ECM detects more than 8 CMP sensor pulses.
3. DTC P0335 runs continuously once the above conditions are met.

The ECM does not detect a signal from the CKP sensor for 5 seconds.

OR

The ECM does not recognize 3 or more reference pulses after the CKP signal is received.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0335

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector. Using this kit prevents damage to the harness or component terminals.
2. The ECM uses the camshaft position sensors to determine engine speed and position when there is a CKP sensor condition.
3. The engine will operate with a CKP sensor condition only if the ECM has stored the learned reference position of the camshafts in memory. With a crankshaft position sensor condition other than a short to voltage in the signal circuit, the engine will go into a limp home mode after a hard restart. The ECM then calculates engine speed from one of the camshaft position sensors. During a limp home mode the following additional DTCs may set and should be ignored: DTC P0324 Knock Sensor (KS) Module Performance DTC P1011 Intake Camshaft Position Actuator Park Position Bank 1
4. A short to voltage in the signal circuit of the CKP sensor will cause the engine to stall or not start and a DTC will not set.
5. An intermittent condition in the CMP actuator solenoid circuits can cause a CKP DTC to set. Inspect the CMP actuator solenoid harness connections and related wiring, if you suspect this condition.
6. The ECM uses a pull-up voltage of 2.5 volts on each CKP sensor circuit to reduce noise interference from electromagnetic interference (EMI). If the voltage is not present, replace the ECM.
7. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if the condition is current.
2. 4: This step tests the resistance of the CKP sensor and wiring. if the resistance is not within the specified range, test the circuits of the CKP sensor for an open or for a wire to wire short. CKP sensor and circuits that measure within the specified range may still have a condition. Test the signal circuit for a short to voltage or a ground and test the low reference circuit for a short to voltage, if the resistance is within the specified range.
3. 6: This step tests the signal circuit of the CKP sensor for a short to ground.
4. 7: This step tests for a short voltage in the signal and low reference circuits of the CKP sensor. If a voltage is present on either of the CKP circuits repair the short to voltage.
5. 8: This step tests if the CKP sensor is capable of generating a signal. Inspect the CKP sensor for the correct installation and the correct fastener torque or for a faulty sensor, if the CKP sensor output is less than the specified value.

DTC P0335 Crankshaft Position (CKP) Sensor Circuit

The crankshaft position (CKP) sensor is located on the rear of bank 1 of the engine block. The CKP sensor produces an AC voltage of different amplitude and frequency depending on the velocity of the crankshaft. The CKP sensor works in conjunction with a 58X reluctor wheel that is attached to the crankshaft. Each tooth on the reluctor wheel is spaced 6 degrees apart with one span having a 12-degree space. The engine control module (ECM) uses the 12-degree space to determine top dead center for cylinders 1 and 4. The ECM determines when cylinder 1 is on the compression stroke by monitoring the CKP sensor and the camshaft position (CMP) sensors. The ECM can synchronize the ignition timing, fuel injector timing and spark knock control based on the CKP sensor and the CMP sensor inputs. If the ECM loses the cylinder 1 crankshaft reference position and must re-sync the engine position, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0336 Crankshaft Position (CKP) Sensor Performance

1. The engine is cranking or operating.
2. The ECM has detected more than 12 camshaft revolutions.
3. DTC P0336 runs continuously once the above conditions are met.

1. The ECM re-syncs the engine position 6 or more times during an ignition cycle. OR
2. The ECM detects 14 or more interruptions in the engine speed signal during an ignition cycle.
3. Either condition exists for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0336

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector. Using this kit prevents damage to the harness or component terminals.
2. The ECM uses the CMP sensors to determine engine speed and position when there is a CKP sensor condition.
3. The engine will operate with a CKP sensor condition only if the ECM has stored the learned reference position of the camshafts in memory. With a crankshaft position sensor condition other than a short to voltage in the signal circuit, the engine will go into a limp home mode after a hard restart. The ECM then calculates engine speed from one of the camshaft position sensors. During a limp home mode the following additional DTCs may set and should be ignored: DTC P0324 Knock Sensor (KS) Module Performance DTC P1011 Intake Camshaft Position Actuator Park Position Bank 1
4. The following conditions may cause this DTC to set: An intermittent condition in the CMP actuator solenoid circuits can cause a CKP DTC to set. Inspect the CMP actuator solenoid harness connections and related wiring, if you suspect this condition. Intermittent short to ground in the signal circuit Excessive air gap between the CKP sensor and the reluctor wheel CKP sensor damage or improper installation Crankshaft reluctor wheel damage or improper installation Foreign material passing between the CKP sensor and the reluctor wheel
5. Excess crankshaft end play causes the reluctor wheel to move out of alignment with the CKP sensor. This could result in any one of the following conditions: A hard start A start and stall Erratic performance
6. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 5: This step is testing for a poor connection at the components and for an intermittent condition with the wiring. Clearing the DTCs allows the ECM to synchronize the cam and crank reference pulses.
2. 6: This step is testing for electromagnetic interference (EMI). If the CKP sensor circuits are routed close to high load circuits or components, this DTC may set.
3. 7: This step is testing if the CKP sensor is installed correctly. A CKP sensor that is not fully seated, may cause this DTC to set.
4. 8: This step is testing for an ECM condition. The ECM uses a pull-up voltage of 2.5 volts on each CKP sensor circuit to reduce noise interference from EMI. If the voltage is not present, replace the ECM.
5. 9: This step is testing for an ECM condition. The ECM uses a pull-up voltage of 2.5 volts on each CKP sensor circuit to reduce noise interference from EMI. If the voltage is not present, replace the ECM.
6. 10: This step tests for a condition in the CKP sensor ground shield. Normal EMI could effect the out-put signal of the CKP sensor if an open or high resistance exists.
7. 12: Missing, damaged or broken teeth on the reluctor wheel can set this DTC. If the crankshaft was recently replaced or the vehicle/engine is new and this DTC is set, inspect all teeth on the reluctor wheel.

P0336 Crankshaft Position (CKP) Sensor Circuit Performance

The crankshaft position (CKP) sensor is located on the rear of bank 1 of the engine block. The CKP sensor produces an AC voltage of different amplitude and frequency depending on the velocity of the crankshaft. The CKP sensor works in conjunction with a 58X reluctor wheel that is attached to the crankshaft. Each tooth on the reluctor wheel are spaced 6 degrees apart with one span having a 12-degree space. The engine control module (ECM) uses the 12-degree space to determine top dead center for cylinders 1 and 4. The ECM determines when cylinder 1 is on the compression stroke by monitoring the CKP sensor and the camshaft position (CMP) sensors. The ECM can synchronize the ignition timing, fuel injector timing and spark knock control based on the CKP sensor and the CMP sensor inputs. If the ECM detects more or less than 58 reference pulses within a certain number of crankshaft revolutions when the engine is cranking or operating, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P0338 Crankshaft Position (CKP) Sensor Circuit High Duty Cycle

1. The engine is cranking or operating.
2. The ECM has detected more than 12 camshaft revolutions.
3. DTC P0338 runs continuously once the above conditions are met.

1. The ECM detects a difference of more than 8 teeth between reference gap position pulses for 4 consecutive crankshaft revolutions in which the same number of pulses are detected each crankshaft revolution.
2. The condition exists for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0338

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector. Using this kit prevents damage to the harness or component terminals.
2. The ECM uses the camshaft position sensors to determine engine speed and position when there is a CKP sensor condition.
3. The engine will operate with a CKP sensor condition only if the ECM has stored the learned reference position of the camshafts in memory. With a crankshaft position sensor condition other than a short to voltage in the signal circuit, the engine will go into a limp home mode after a hard restart. The ECM then calculates engine speed from one of the CMP sensors. During a limp home mode the following additional DTCs may set and should be ignored: DTC P0324 Knock Sensor (KS) Module Performance DTC P1011 Intake Camshaft Position Actuator Park Position Bank 1
4. The following conditions may cause this DTC to set: An intermittent condition in the CMP actuator solenoid circuits can cause a CKP DTC to set. Inspect the CMP actuator solenoid harness connections and related wiring, if you suspect this condition. Intermittent short to ground in the signal circuit Excessive air gap between the CKP sensor and the reluctor wheel CKP sensor damage or improper installation Crankshaft reluctor wheel damage or improper installation Foreign material passing between the CKP sensor and the reluctor wheel
5. Excess crankshaft end play causes the reluctor wheel to move out of alignment with the CKP sensor. This could result in any one of the following conditions: A hard start A start and stall Erratic performance
6. For an intermittent, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 5: This step is testing for a poor connection at the components and for an intermittent condition with the wiring. Clearing the DTCs allows the ECM to synchronize the cam and crank reference pulses.
2. 6: This step is testing for electromagnetic interference (EMI). If the CKP sensor circuits are routed close to high load circuits or components, this DTC may set.
3. 7: This step is testing if the CKP sensor is installed correctly. A CKP sensor that is not fully seated, may cause this DTC to set.
4. 8: This step is testing for an ECM condition. The ECM uses a pull-up voltage of 2.5 volts on each CKP sensor circuit to reduce noise interference from EMI. If the voltage is not present, replace the ECM.
5. 9: This step is testing for an ECM condition. The ECM uses a pull-up voltage of 2.5 volts on each CKP sensor circuit to reduce noise interference from EMI. If the voltage is not present, replace the ECM.
6. 10: This step tests for a condition in the CKP sensor ground shield. Normal EMI could effect the out-put signal of the CKP sensor if an open or high resistance exists.
7. 12: Missing, damaged or broken teeth on the reluctor wheel can set this DTC. If the crankshaft was recently replaced or the vehicle/engine is new and this DTC is set, inspect all teeth on the reluctor wheel.

P0338 Crankshaft Position (CKP) Sensor Circuit High Duty Cycle

Each camshaft is equipped with a camshaft position (CMP) sensor that the engine control module (ECM) monitors. The CMP sensor is a hall effect switch that works in conjunction with a 4X reluctor wheel. The reluctor wheels are mounted to the camshaft position actuators that are mounted to the end of the camshafts. The ECM uses the CMP sensor signals in order to determine the position of the camshafts.

The ECM supplies 5 volts to the CMP sensors on the 5-volt reference circuits and supplies a ground on the low reference circuits. The CMP sensors provide a signal to the ECM on the signal circuits. If the ECM detects extra or missing CMP sensor signal transitions within a certain number of crankshaft revolutions, this DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P0341 Intake Camshaft Position (CMP) Sensor Performance Bank 1
2. DTC P0346 Intake Camshaft Position (CMP) Sensor Performance Bank 2
3. DTC P0366 Exhaust Camshaft Position (CMP) Sensor Performance Bank 1
4. DTC P0391 Exhaust Camshaft Position (CMP) Sensor Performance Bank 2

DTCs P0341, P0346, P0366 and P0391 run continuously once the engine is operating for more than 1 second.

1. The ECM detects a signal from the CMP sensor, but the number of pulses are at least 5 less than or more than what is expected for one crankshaft revolution. OR
2. The CMP sensor does NOT correlate to the crankshaft position.
3. Either condition exists for more 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0341, P0346, P0366 or P0391

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step verifies that the condition is present.
2. 5: This step inspects for electromagnetic interference (EMI) on the CMP sensor circuits.

DTC P0341, P0346, P0366 or P0391

Each camshaft is equipped with a camshaft position (CMP) sensor that the engine control module (ECM) monitors. The CMP sensor is a hall effect switch that works in conjunction with a 4X reluctor wheel. The reluctor wheels are mounted to the camshaft position actuators that are mounted to the end of the camshafts. The ECM uses the CMP sensor signals in order to determine the position of the camshafts.

The ECM supplies 5 volts to the CMP sensors on the 5-volt reference circuits and supplies a ground on the low reference circuits. The CMP sensors provide a signal to the ECM on the signal circuits. If the ECM detects the CMP signal voltage is less than a predetermined voltage, within a certain number of crankshaft revolutions, this DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P0342 Intake Camshaft Position (CMP) Sensor Circuit Low Voltage Bank 1
2. DTC P0347 Intake Camshaft Position (CMP) Sensor Circuit Low Voltage Bank 2
3. DTC P0367 Exhaust Camshaft Position (CMP) Sensor Circuit Low Voltage Bank 1
4. DTC P0392 Exhaust Camshaft Position (CMP) Sensor Circuit Low Voltage Bank 2

DTCs P0342, P0347, P0367, P0392 run continuously once the engine is operating for more than 1 second.

The CMP sensor signal voltage is always low and the ECM detects no pulses from the CMP sensor for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0342, P0347, P0367 or P0392

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines that the condition is present.
2. 4: This step tests the signal circuit of the CMP sensor. This circuit is pulled-up to about 5 volts.
3. 5: This step tests for high resistance in the low reference circuit of the CMP sensors. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM fuse or the PCM/ETC fuse, allows the ECM to power down completely.

DTC P0342, P0347, P0367 or P0392

Each camshaft is equipped with a camshaft position (CMP) sensor that the engine control module (ECM) monitors. The CMP sensor is a hall effect switch that works in conjunction with a 4X reluctor wheel. The reluctor wheels are mounted to the CMP actuators that are mounted to the end of the camshafts. The ECM uses the CMP sensor signals in order to determine the position of the camshafts.

The ECM supplies 5 volts to the CMP sensors on the 5-volt reference circuits and supplies a ground on the low reference circuits. The CMP sensors provide a signal to the ECM on the signal circuits. If the ECM detects the CMP signal voltage is more than a predetermined voltage, within a certain number of crankshaft revolutions, this DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P0343 Intake Camshaft Position (CMP) Sensor Circuit High Voltage Bank 1
2. DTC P0348 Intake Camshaft Position (CMP) Sensor Circuit High Voltage Bank 2
3. DTC P0368 Exhaust Camshaft Position (CMP) Sensor Circuit High Voltage Bank 1
4. DTC P0393 Exhaust Camshaft Position (CMP) Sensor Circuit High Voltage Bank 2

DTCs P0343, P0348, P0368, P0393 run continuously once the engine is operating for more than 1 second.

The CMP sensor signal voltage is always high and the ECM detects no pulses from the CMP sensor for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0343, P0348, P0368 or P0393

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines that the condition is present.
2. 4: This step tests the signal circuit of the CMP sensor. This circuit is pulled-up to about 5 volts.
3. 5: The ECM produces a measurable steady-state amperage that provides the 5-volt reference to the CMP sensors. If the amperage on the 5-volt reference circuit is less than the specified value, test for a condition in the 5-volt reference circuit.
4. 6: This step tests for high resistance in the low reference circuit of the CMP sensors. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM fuse or the PCM/ETC fuse, allows the ECM to power down completely.

DTC P0343, P0348, P0368 or P0393

The ignition system on this engine uses individual ignition coils and ignition control (IC) circuits for each cylinder. The engine control module (ECM) controls the ignition system operation. The ECM controls each coil using the IC circuits. The ECM commands the IC circuit low when a spark event is requested. Each ignition coil is supplied the following circuits

1. The IC circuit
2. The ignition 1 voltage circuit
3. Two ground circuits

The sequencing and timing are ECM controlled. If the ECM detects the ignition control circuit is open, this DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P0351 Ignition Coil 1 Control Circuit
2. DTC P0352 Ignition Coil 2 Control Circuit
3. DTC P0353 Ignition Coil 3 Control Circuit
4. DTC P0354 Ignition Coil 4 Control Circuit
5. DTC P0355 Ignition Coil 5 Control Circuit
6. DTC P0356 Ignition Coil 6 Control Circuit

1. The engine is operating.
2. The engine speed is between 480-5,000 RPM.
3. The ignition 1 voltage is between 10.5-18 volts.
4. DTCs P0351, P0352, P0353, P0354, P0355 and P0356 run continuously once the above conditions are met.

1. The ECM detects an open in the IC circuit.
2. The condition is present for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The following table illustrates the ECM connector locations

DTC P0351-P0356

1. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
2. Inspect the ignition coils for aftermarket devices. An aftermarket device connected to the ignition coil circuits, may cause this DTC to set.
3. For an intermittent condition, refer to «Intermittent Conditions»(/buick/lacrosse/i-2004-2009/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if there is a condition with an ignition coil.
2. 4: This step tests the ignition control circuit of the ignition coil. If the frequency is not within the specified range, there is a condition with the ignition control circuit or the ECM.
3. 6: This step tests the ignition 1 voltage supply to the ignition coil.
4. 7: This step tests the ground circuits of the ignition coil. A high resistance in one of the ground circuits will cause a condition. Repair the ground circuits if the resistance is more than the specified value.

P0351-P0356 Ignition Coil 1-6 Control Circuit

In order to maintain a reasonably low emission level of hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOx) a 3-way catalytic converter (TWC) is used. The catalyst within the converter promotes a chemical reaction that oxidizes the HC and CO present in the exhaust gas. This reaction converts the gases into harmless water vapor and carbon dioxide. The catalyst also reduces the NOx, converting the NOx into nitrogen. The engine control module (ECM) monitors this process using the post catalyst heated oxygen sensor (HO2S) signal. The post-catalyst HO2S located in the exhaust stream after the TWC, produces an output signal that indicates the oxygen storage capacity of the catalyst. The oxygen storage capacity (OSC) determines the ability of the catalyst to convert the exhaust emissions effectively. If the catalyst is functioning correctly, the post-catalyst HO2S signal will be far less active than the signal produced by the pre-catalyst HO2S.

To determine OSC, the ECM commands a rich air/fuel mixture until all oxygen is removed from the catalyst. The ECM then commands a lean air/fuel mixture and monitors the rear heated oxygen sensors to calculate the oxygen storage capacity. The catalyst is operated in this mode until one of the following conditions occur

1. The oxygen stored in the catalyst exceeds a calibrated threshold, which is determined from the rear HO2S signal.
2. The rear HO2S indicates the catalyst to be completely saturated with oxygen, which is determined from the rear HO2S signal.

If the ECM detects an excessive post-catalyst signal activity outside of an acceptable range for an extended period of time, this DTC sets. This indicates that the TWC oxygen storage capacity is below a threshold considered acceptable.

This diagnostic procedure supports the following DTC

DTC P0420 Catalyst System Low Efficiency

1. Before the ECM can report DTC P0420 failed, DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0101, P0102, P0103, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0135, P0137, P0138, P0140, P0141, P0221, P0222, P0223, P0335, P0336, P0338, P167A, P2096, P2097, P2195, P2196, P2231, P2232, P2237, P2243, P2251, P2270, P2271, P2297 and P2626, must run and pass.
2. DTCs P0010, P0011, P0013, P0014, P0020, P0021, P0023, P0024, P0030, P0031, P0032, P0036, P0037, P0038, P0101, P0102, P0103, P0117, P0118, P0121, P0122, P0123, P0125, P0130, P0131, P0132, P0133, P0135, P0137, P0138, P0140, P0141, P0221, P0222, P0223, P0300, P0443, P0458, P0459, P0496, P2088, P2089, P2090, P2091, P2092, P2093, P2094, P2095, P2096, P2097, P2100, P2101, P2107, P2119, P2122, P2123, P2127, P2128, P2138, P2176, P2177, P2178, P2187, P2188, P2195, P2196, P2232, P2237, P2243, P2251, P2270, P2271, P2297 and P2626, are not set.
3. The air flow into the engine is between 10-42 g/s and not changing more than 8 g/s
4. The engine coolant temperature (ECT) at engine start-up is more than -9°C (-16°F).
5. The engine is operating for more than 320 seconds.
6. The engine is operating in Closed Loop.
7. The calculated TWC temperature is between 465°C (869°F) and 630°C (1,166°F) and steady.
8. DTC P0420 runs once per ignition cycle when the above conditions exist for approximately 17 minutes. The ECM will restart the test up to 4 times per ignition cycle, if the conditions above are interrupted during the test.

1. The ECM determines that the catalyst efficiency has degraded below a calibrated threshold.
2. The condition exists for more than 4 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the 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 the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

P0420 or P0430 Catalyst System Low Efficiency Bank 1 or 2

See also:
• Intermittent Conditions
• Engine Controls Schematics
• Engine Control Module (ECM) Connector End Views
• Engine Controls Connector End Views
• Diagnostic System Check - Vehicle
• Measuring Voltage Drop
• Circuit Testing
• Wiring Repairs
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Control Module References
• Diagnostic Trouble Code (DTC) List - Vehicle
• Fuel Injector Balance Test with Special Tool
• Symptoms - Engine Exhaust
• Intake Manifold Replacement - Upper
• DISENGAGING CONNECTORS NOTICE
• Symptoms - Engine Mechanical
• Spark Plug Inspection
• Restricted Exhaust
• Special Tools
• Diagnostic Starting Point - Antilock Brake System
• Fastener Tightening Specifications
• Lifting and Jacking the Vehicle
• Crankshaft and Bearings Cleaning and Inspection
• DTC P0118
• Measuring Frequency
• DTC P0301-P0306