Engine Control System - 3.6l (ly7) - DTC p2231 to DTC p2626 Buick LaCrosse I

Circuit Description

The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust system and provides more information than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The engine control module (ECM) supplies a voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a constant voltage in the oxygen sensing cell. The ECM monitors the voltage variation in the sensing cell and attempts to keep the voltage constant by increasing or decreasing the amount of current flow or oxygen ion flow, to the pumping cell. By measuring the amount of current required to maintain the voltage in the sensing cell, the ECM can determine the concentration of oxygen in the exhaust. The HO2S voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the fuel system is lean, the oxygen level will be high and the lambda signal will be high or more than 1. When the fuel system is rich, the oxygen level will be low and the lambda signal will be low or less than 1. The ECM uses this information to maintain the correct air/fuel ratio.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC P2231 HO2S Signal Circuit Shorted to Heater Circuit Sensor 1

Conditions for Running the DTC

1. Before the ECM can report DTC P2231 failed, DTCs P0030, P0031, P0032, P0053, P0101, P0102, P0103, P0130, P0135 and P0167A must run and pass.
2. DTCs P0461, P0462 and P0463 are not set.
3. The HO2S heater control is enabled.
4. The HO2S heater duty cycle is more than 5 percent.
5. The HO2S heater is at operating temperature for more than 10 seconds.
6. The ECM does not detect a misfire condition.
7. The fuel injectors are enabled.
8. The ignition 1 voltage is between 10.5-18 volts.
9. The calculated exhaust temperature is less than 800°C (1,472°F).
10. DTC P2231 runs continuously once the above conditions are met for more than 10 seconds.
11. DTC P2231 runs continuously once the above conditions are met for more than 10 minutes if the fuel level is lass than 12 percent.

Conditions for Setting the DTC

1. The ECM detects the internal HO2S voltage signal change is more than 300 mV as the heater control switches.
2. The above condition occurs 18 times within 10 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 P2231

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 sensor does 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 a condition with the HO2S circuits, the ECM commands Open Loop for the applicable sensor.
2. 5: 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 the reference voltage circuit or the low reference circuit of the HO2S is shorted to a voltage, the bias voltage will be more than the specified value, which indicates there is a condition with the circuits.

DTC P2231

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. If the ECM detects that the HO2S signal voltage switches at the same rate that the ECM is commanding the heater, which indicates the signal circuit is shorted to the heater circuit, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P2232 HO2S Signal Circuit Shorted to Heater Circuit 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 P2232 runs continuously once the above conditions are met for more than 90 seconds.

1. The ECM detects that the HO2S signal voltage increases more than 2 volts in less than 1 second of the HO2S heater switching OFF.
2. The above condition occurs 4 times out of 6 as the heater is turned OFF.

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 P2232

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 should be between 350-550 mV with the ignition On. If the voltage is more than the specified value, there is a condition with the HO2S circuits.
2. 4: This step isolates the condition. If the voltage does not change after disconnecting the HO2S, the condition is between the sensor and the ECM. If the voltage is between 350-550 mV after disconnecting the sensor, the condition is with the HO2S.
3. 6: This step inspects the harness connector for water intrusion. Moisture in a connector may cause voltage to bleed to other circuits within the connector.
4. 7: This step inspects the harness connector for water intrusion. Moisture in a connector may cause voltage to bleed to other circuits within the connector.

DTC P2232

The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust system and provides more information than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The engine control module (ECM) supplies a voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a constant voltage in the oxygen sensing cell. The ECM monitors the voltage variation in the sensing cell and attempts to keep the voltage constant by increasing or decreasing the amount of current flow or oxygen ion flow, to the pumping cell. By measuring the amount of current required to maintain the voltage in the sensing cell, the ECM can determine the concentration of oxygen in the exhaust. The HO2S voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the fuel system is lean, the oxygen level will be high and the lambda signal will be high or more than 1. When the fuel system is rich, the oxygen level will be low and the lambda signal will be low or less than 1. The ECM uses this information to maintain the correct air/fuel ratio.

This diagnostic procedure supports the following DTC

DTC P2237 HO2S Pumping Current Control Circuit Sensor 1

Condition 1

1. Before the ECM can report DTC P2237 failed, DTCs P0101, P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336 and P0338 must run and pass.
2. DTCs P0030, P0031, P0032, P0133 and P0135 are not set.
3. The ignition 1 voltage is between 10.7-18 volts.
4. The engine is operating in Closed Loop.
5. The HO2S heater is at operating temperature.
6. The ECM is commanding the lambda more than 1.03 or less than 0.97.
7. More than 200 grams of exhaust gas has passed.
8. DTC P2237 runs continuously once the above conditions are met for approximately 8 seconds.

Condition 2

1. Before the ECM can report DTC P2237 failed, DTCs P0101, P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336 and P0338 must run and pass.
2. The ignition 1 voltage is between 10.7-18 volts.
3. The engine is operating in Closed Loop.
4. The HO2S heater is at operating temperature.
5. The ECM detects the internal HO2S signal voltage is between 1.48-1.52 volts.
6. The ECM is commanding the lambda rich and then lean periodically with a change of more than 2 percent.
7. DTC P2237 runs continuously once the above conditions are met for more than 1.5 seconds.

Condition 3

1. Before the ECM can report DTC P2237 failed, DTCs P0101, P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336 and P0338 must run and pass.
2. The ignition 1 voltage is between 10.7-18 volts.
3. The HO2S heater is at operating temperature.
4. The ECM is commanding decel fuel cut-off for more than 3 seconds.
5. DTC P2237 runs continuously once the above conditions are met for more than 2 seconds.

1. The ECM detects the internal HO2S signal voltage is between 1.48-1.52 volts while the desired lambda is above or below a threshold.
2. The above condition exists for more than 4 seconds.

1. The ECM stores the fuel trim control values after the above conditions are met. The ECM detects that the stored value and the current fuel trim control value deviates more than 10 percent of the lambda value.
2. The above condition exists for more than 4 seconds.

1. The ECM detects the internal HO2S signal voltage after a decel fuel shut-off is less than 1.7 volts.
2. The above 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 P2237

1. 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.
2. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
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

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

1. 2: This step determines if the condition exists. The HO2S lambda parameter should react immediately to the changes in throttle position when performing this test.
2. 4: This step determines if there is a condition with the pumping current circuit. Connecting a jumper wire between the reference voltage and the low reference circuits causes the ECM to command the pumping current and the input pumping current circuits.

DTC P2237

The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust system and provides more information than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The engine control module (ECM) supplies a voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a constant voltage in the oxygen sensing cell. The ECM monitors the voltage variation in the sensing cell and attempts to keep the voltage constant by increasing or decreasing the amount of current flow or oxygen ion flow, to the pumping cell. By measuring the amount of current required to maintain the voltage in the sensing cell, the ECM can determine the concentration of oxygen in the exhaust. The HO2S voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the fuel system is lean, the oxygen level will be high and the lambda signal will be high or more than 1. When the fuel system is rich, the oxygen level will be low and the lambda signal will be low or less than 1. The ECM uses this information to maintain the correct air/fuel ratio.

This diagnostic procedure supports the following DTC

DTC P2243 HO2S Reference Voltage Circuit Sensor 1

1. Before the ECM can report DTC P2243 failed, DTC P0030, P0031, P0032 and P0135 must run and pass.
2. The engine is operating.
3. The ignition 1 voltage is between 10.7-18 volts
4. The internal HO2S sensing element resistance is more than 570 ohms.
5. The HO2S heater is at operating temperature for more than 30 seconds.
6. DTC P2243 runs continuously once the above conditions are met for more than 2 seconds.

The ECM detects the internal HO2S signal voltage is less than 0.2 volts or more than 4.7 volts for more than 1 second.

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 P2243

1. 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.
2. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
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

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

1. 2: This step determines if the condition exists. If there is a condition with the HO2S circuits, the ECM commands Open Loop for the applicable sensor.
2. 5: This step tests for a bias voltage across the reference voltage circuit and the low reference circuit of the HO2S. If the reference voltage circuit of the HO2S is open, the bias voltage will be above 1.5 volts, which indicates there is a condition with the circuit.

DTC P2243

The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust system and provides more information than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The engine control module (ECM) supplies a voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a constant voltage in the oxygen sensing cell. The ECM monitors the voltage variation in the sensing cell and attempts to keep the voltage constant by increasing or decreasing the amount of current flow or oxygen ion flow, to the pumping cell. By measuring the amount of current required to maintain the voltage in the sensing cell, the ECM can determine the concentration of oxygen in the exhaust. The HO2S voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the fuel system is lean, the oxygen level will be high and the lambda signal will be high or more than 1. When the fuel system is rich, the oxygen level will be low and the lambda signal will be low or less than 1. The ECM uses this information to maintain the correct air/fuel ratio.

DTC Descriptors

This diagnostic procedure supports the following DTC

DTC P2251 HO2S Reference Ground Circuit Sensor 1

1. Before the ECM can report DTC P2251 failed, DTC P0030, P0031, P0032 and P0135 must run and pass.
2. The ignition 1 voltage is between 10.7-18.0 volts for more than 30 seconds.
3. The HO2S heater control is enabled.
4. The ECM has not commanded fuel cut-off for more than 2 seconds.
5. The HO2S heater is at operating temperature for more than 20 seconds.
6. The internal HO2S sensing element resistance is more than 570 ohms.
7. The calculated exhaust temperature is less than 900°C (1,652°F).
8. The ECM detects the internal HO2S signal voltage is between 1.47-1.53 volts.
9. DTC P2251 runs continuously once the above conditions are met for more than 10 seconds.

1. The ECM detects the internal HO2S voltage signal change is more than 012 mV as the heater control switches.
2. The above condition occurs 20 times within 10 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 P2251

1. 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.
2. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
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

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

1. 2: This step determines if the condition exists. The HO2S lambda parameter should react immediately to the changes in throttle position when performing this test.
2. 5: 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 the specified value, which indicates there is a condition with the circuits.

DTC P2251

The engine control module (ECM) supplies a voltage near 450 mV between the heated oxygen sensor (HO2S) 2 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.

1. The ECM monitors the HO2S 2 voltage to determine if the signal voltage goes above a predetermined threshold within a certain amount of time. If the ECM determines that the signal voltage remains below a threshold, the ECM commands a rich condition. If the signal voltage does not go above the threshold within a certain amount of time after commanding the system rich, this DTC sets.
2. The ECM monitors the HO2S 2 voltage during power enrichment. If the ECM determines that the signal voltage is less than a predetermined voltage during power enrichment, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P2270 HO2S Signal Stuck Lean Sensor 2

1. Before the ECM can report DTC P2270 failed, DTCs P0036, P0037, P0038, P137, P0138, P0140, P0141, P0341, P0342, P0343, P0346, P0347, P0348, P0366, P0367, P0368, P0391, P0392, P0393, P0443, P0458 and P0459 must run and pass.
2. DTCs P0461, P0462 and P0463 are not set.
3. The engine is operating.
4. The rear heated oxygen sensor is at operating temperature for more than 10 seconds.
5. The long term fuel control is enabled.
6. The mass air flow (MAF) sensor is more than 10 g/s.
7. The MAF sensor is between 8-33 g/s for more than 3 seconds during the intrusive test.
8. DTC P2270 runs continuously once the above conditions are met for approximately 10 minutes.
9. DTC P2270 runs continuously once the above conditions are met for approximately 20 minutes if the fuel level is less than 12 percent.

If the ECM detects that the rear HO2S voltage is less than 740 mV for more than 100 seconds, then an intrusive test is performed. The ECM will enrich the fuel mixture up to 30 percent and then wait for 10 seconds at 30 percent. If the ECM detects that the HO2S voltage is still less than 740 mV, this 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.

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 P2270

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. A fuel delivery condition causes this DTC to set. Thoroughly inspect all items that cause a lean condition.
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. 5: This step is testing for a rear HO2S sensor circuit condition. A circuit condition sets this DTC.
3. 8: This step is testing for an intermittent circuit condition. Thoroughly inspect the HO2S circuits for an intermittent circuit condition.

P2270 HO2S Signal Stuck Lean

The engine control module (ECM) supplies a voltage near 450 mV between the heated oxygen sensor (HO2S) 2 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.

1. The ECM monitors the HO2S voltage to determine if the signal voltage goes below a predetermined threshold within a certain amount of time. If the ECM determines that the signal voltage remains above a threshold, the ECM commands a lean condition. If the signal voltage does not go below the threshold within a certain amount of time after commanding the system lean, this DTC sets.
2. The ECM monitors the HO2S voltage during fuel cut-off. If the ECM determines that the signal voltage is more than a predetermined voltage during fuel cut-off, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P2271 HO2S Signal Stuck Rich Sensor 2

1. Before the ECM can report DTC P2271 failed, DTCs P0341, P0342, P0343, P0346, P0347, P0348, P0366, P0367, P0368, P0391, P0392, P0393, P0443, P0458 and P0459 must run and pass.
2. DTCs P0442, P0455, P0496, P0560, P0562 and P0563 are not set.
3. The engine is operating.
4. The rear HO2S is at operating temperature for more than 10 seconds.
5. The HO2S 2 is in closed loop.
6. The HO2S 2 heating is stable for more than 10 seconds.
7. The HO2S 2 is more than a calculated temperature for at least 30 seconds.
8. The calculated exhaust temperature is more than 350°C (662°F).
9. The mass air flow (MAF) sensor is between 8-33 g/s for more than 3 seconds during the intrusive test.
10. The measured airflow is more than 15 g during the decel fuel cut-off test.
11. DTC P2271 runs continuously once the above conditions are met.

If the ECM detects that the rear HO2S 2 voltage is more than 740 mV for more than 100 seconds, then an intrusive test is performed. The ECM will lean the fuel mixture up to -7 percent and then wait for 10 seconds at -7 percent. If the ECM detects that the HO2S 2 voltage is still more than 740 mV, the ECM then tests the HO2S 2 at the next decel fuel cut-off. If the ECM detects the HO2S 2 voltage is more than 202 mV after 4 seconds in decel fuel cut-off, this 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.

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 P2271

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. A fuel delivery condition causes this DTC to set. Thoroughly inspect all items that cause a rich condition.
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. 5: This step is testing for a rear HO2S sensor circuit condition. A circuit condition sets this DTC.
3. 8: This step is testing for an intermittent circuit condition. Thoroughly inspect the HO2S 2 circuits for an intermittent circuit condition.

P2271 HO2S Signal Stuck Rich

The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust system and provides more information than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The engine control module (ECM) supplies a voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a constant voltage in the oxygen sensing cell. The ECM monitors the voltage variation in the sensing cell and attempts to keep the voltage constant by increasing or decreasing the amount of current flow or oxygen ion flow, to the pumping cell. By measuring the amount of current required to maintain the voltage in the sensing cell, the ECM can determine the concentration of oxygen in the exhaust. The HO2S voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the fuel system is lean, the oxygen level will be high and the lambda signal will be high or more than 1. When the fuel system is rich, the oxygen level will be low and the lambda signal will be low or less than 1. The ECM uses this information to maintain the correct air/fuel ratio.

This diagnostic procedure supports the following DTC.

DTC P2297 HO2S Performance During Decel Fuel Cut-Off (DFCO) Sensor 1

Condition 1

1. Before the ECM can report DTC P2297 failed, DTC P0130 must run and pass.
2. The HO2S 1 is at operating temperature.
3. The desired HO2S 1 is less than 1.6 lambda.
4. The internal ECM HO2S signal voltage is less than 4.81 volts.
5. The fuel injectors are enabled.
6. DTC P2297 runs continuously once the above conditions are met.

Condition 2

1. A decel fuel cut-off has occurred 11 times with successful adjustments.
2. DTC P2297 runs continuously once the above condition is met.

The ECM detects that the internal HO2S signal voltage is more than 3.7 volts for more than 10 seconds.

If the ECM detects that the compensation factor of the HO2S is less than -25 percent or more than 30 percent of the expected value, this 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.

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. 4: An HO2S that is not installed into the exhaust system causes this DTC to set.

DTC P2297

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 shorted to ground, this DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P2300 Ignition Coil 1 Control Circuit Low Voltage
2. DTC P2303 Ignition Coil 2 Control Circuit Low Voltage
3. DTC P2306 Ignition Coil 3 Control Circuit Low Voltage
4. DTC P2309 Ignition Coil 4 Control Circuit Low Voltage
5. DTC P2312 Ignition Coil 5 Control Circuit Low Voltage
6. DTC P2315 Ignition Coil 6 Control Circuit Low Voltage

1. The engine is operating.
2. The engine speed is between 480-5,000 RPM.
3. The ignition voltage is between 10.5-18 volts.
4. This DTC runs continuously once the above conditions are met.

1. The ECM detects the ignition control circuit is shorted to ground.
2. The above condition is present 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 P2300, P2303, P2306, P2309, P2312 or P2315

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 number below refers to the step number on the diagnostic table.

1. 4: This step tests that the ECM is commanding the ignition coil ON and OFF via the ignition control circuit. If the frequency is not between 3-20 Hz, test the ignition control circuit for a short to ground.

P2300, P2303, P2306, P2309, P2312 or P2315 Ignition Coil Control Circuit Low Voltage

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 IC circuit is shorted to voltage, this DTC sets.

This diagnostic procedure supports the following DTCs

1. DTC P2301 Ignition Coil 1 Control Circuit High Voltage
2. DTC P2304 Ignition Coil 2 Control Circuit High Voltage
3. DTC P2307 Ignition Coil 3 Control Circuit High Voltage
4. DTC P2310 Ignition Coil 4 Control Circuit High Voltage
5. DTC P2313 Ignition Coil 5 Control Circuit High Voltage
6. DTC P2316 Ignition Coil 6 Control Circuit High Voltage

1. The engine is operating.
2. The engine speed is between 480-5,000 RPM.
3. The ignition voltage is between 10.5-18 volts.
4. This DTC runs continuously once the above conditions are met.

1. The ECM detects the IC circuit is shorted to voltage.
2. The above condition is present 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 P2301, P2304, P2307, P2310, P2313 or P2316

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 number below refers to the step number on the diagnostic table.

1. 4: This step tests that the ECM is commanding the ignition coil ON and OFF via the IC circuit. If the frequency is not between 3-20 Hz, test the ignition control circuit for a short to voltage.

P2301, P2304, P2307, P2310, P2313 or P2316 Ignition Coil Control Circuit High Voltage

The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust system and provides more information than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The engine control module (ECM) supplies a voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a constant voltage in the oxygen sensing cell. The ECM monitors the voltage variation in the sensing cell and attempts to keep the voltage constant by increasing or decreasing the amount of current flow or oxygen ion flow, to the pumping cell. By measuring the amount of current required to maintain the voltage in the sensing cell, the ECM can determine the concentration of oxygen in the exhaust. The HO2S voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the fuel system is lean, the oxygen level will be high and the lambda signal will be high or more than 1. When the fuel system is rich, the oxygen level will be low and the lambda signal will be low or less than 1. The ECM uses this information to maintain the correct air/fuel ratio.

This diagnostic procedure supports the following DTC

DTC P2626 HO2S Pumping Current Trim Circuit Sensor 1

1. Before the ECM can report DTC P2626 failed, DTCs P0101, P0121, P0122, P0123, P0221, P0222, P0223, P0336 and P0338 must run and pass.
2. The engine is operating.
3. The ignition 1 voltage is between 10.7-18 volts.
4. The fuel system is in fuel shut-off for more than 5 seconds.
5. The calculated exhaust temperature is less than 750°C (1,382°F).
6. The heated oxygen sensors are at operating temperature.
7. DTC P2626 runs continuously once the above conditions are met.

1. The ECM internal HO2S voltage is more than 4.73 volts.
2. The condition exists for more than 4 seconds or 600 seconds if the fuel level is less than 12 percent.

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 P2626

1. 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.
2. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
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

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

1. 2: This step determines if the condition exists. The HO2S lambda parameter should react immediately to the changes in throttle position when performing this test.
2. 5: This step determines if there is a condition with the pumping current circuit. Connecting a jumper wire between the reference voltage and the low reference circuits causes the ECM to command the pumping current and the input pumping current circuits.

DTC P2626

See also:
• Intermittent Conditions
• Engine Controls Schematics
• Engine Control Module (ECM) Connector End Views
• Engine Controls Connector End Views
• Diagnostic System Check - Vehicle
• Diagnostic Trouble Code (DTC) List - Vehicle
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Control Module References
• Circuit Testing
• Wiring Repairs
• Symptoms - Engine Exhaust
• Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool)
• Symptoms - Engine Mechanical
• Measuring Frequency
• Testing for Short to Ground
• Diagnostic Aids
• Diagnostic Aids