Engine Control System - 3.6l (ly7) (DTC p2195 to DTC u0423) Cadillac STS 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 Descriptors

This diagnostic procedure supports the following DTCs

1. DTC P2195 HO2S Signal Biased Lean Bank 1 Sensor 1
2. DTC P2197 HO2S Signal Biased Lean Bank 2 Sensor 1

Conditions for Running the DTC

Condition 1 and 2

1. Before the ECM can report DTC P2195 or P2197 failed, DTCs P0137, P0138, P0140, P0141, P0157, P0158, P0160, P0161, P2270, P2271, P2272, and P2273 must run and pass.
2. The front and rear heated oxygen sensors are at operating temperature.
3. The rear HO2S voltage signal is more than 850 mV.
4. The front HO2S is more than 1.08 lambda.
5. The Loop Status for both the front and rear sensors is Closed Loop.
6. DTC P2195 and P2197 run continuously once the above conditions are met.

Conditions for Setting the DTC

Condition 1

1. The ECM detects that the front HO2S is operating too lean while the rear HO2S is operating too rich and the ECM detects that the fuel trim is at maximum control. OR
2. The rear fuel trim, long and short term, is more than a threshold.
3. This DTC sets after the air flow coming into the engine accumulates to more than 200 grams and the above conditions are met for more than 4 seconds.

Condition 2

1. The ECM detects that the rear HO2S is operating too rich while the ECM is commanding a lean air/fuel mixture.
2. This DTC sets after the air flow coming into the engine accumulates to more than 800 grams and the above condition is met 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

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 lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

Test Description

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.
4. 9: This step is testing for an intermittent circuit condition. Thoroughly inspect the HO2S circuits for an intermittent circuit condition.

DTC P2195 or P2197 HO2S Signal Biased Lean

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 DTCs

1. DTC P2196 HO2S Signal Biased Rich Bank 1 Sensor 1
2. DTC P2198 HO2S Signal Biased Rich Bank 2 Sensor 1

Condition 1 and 2

1. Before the ECM can report DTC P2196 or P2198 failed, DTCs P0137, P0138, P0140, P0141, P0157, P0158, P0160, P0161, P2270, P2271, P2272, and P2273 must run and pass.
2. The front and rear HO2S are at operating temperature.
3. The rear HO2S voltage signal is more than 150 mV.
4. The front HO2S is more than 0.92 lambda.
5. The Loop Status for both the front and rear sensors is Closed Loop.
6. DTC P2196 and P2198 runs continuously once the above conditions are met.

Condition 1

1. The ECM detects that the front HO2S is operating too rich while the rear is operating too lean, and the ECM detects that the fuel trim is at minimum control. OR
2. The rear fuel trim, long and short term, is less than a threshold.
3. This DTC sets after the air flow coming into the engine accumulates to more than 200 grams and the above conditions are met for more than 4 seconds.

Condition 2

1. The ECM detects that the rear HO2S is operating too lean while the ECM is commanding a rich air/fuel mixture.
2. This DTC sets after the air flow coming into the engine accumulates to more than 800 grams and the above condition is 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.

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 lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/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.
4. 9: This step is testing for an intermittent circuit condition. Thoroughly inspect the HO2S circuits for an intermittent circuit condition.

DTC P2196 or P2198

The barometric pressure (BARO) sensor responds to changes in altitude and atmospheric conditions. This gives the engine control module (ECM) an indication of BARO. The ECM uses this information to calculate fuel delivery. The BARO sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The ECM supplies 5 volts to the BARO sensor on a 5-volt reference circuit, and provides a ground on a low reference circuit. The BARO sensor provides a voltage signal to the ECM on a signal circuit relative to the atmospheric pressure changes. The ECM monitors the BARO sensor signal for a voltage outside of the normal range. If the ECM detects the actual BARO sensor signal is not within a predetermined range of the calculated BARO sensor value, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC P2227 Barometric Pressure (BARO) Sensor Performance

1. Before the ECM can report DTC P2227 failed, DTCs P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336, P0338, P2228, and P2229 must run and pass.
2. The engine is operating for more than 20 seconds.
3. The mass air flow is more than 11 g/s.
4. The difference between the calculated manifold absolute pressure (MAP) and BARO pressure is less than 1.0 kPa for more than 3 seconds.
5. DTC P2227 runs continuously once the above conditions are met for 2 seconds.

1. The ECM detects that the BARO pressure changed more than 5 kPa within 20 seconds. OR
2. The ECM detects that the BARO pressure changed more than 30 kPa since the last ignition cycle.
3. The conditions exist 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.

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 lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/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. 7: This step is testing the signal circuit. The signal circuit is pulled up to a voltage, so the scan tool should display a voltage within the specified range. If the voltage is low, this indicates the signal circuit is grounded.
3. 8: This step is testing the signal circuit. The signal circuit is pulled up to a voltage. The scan tool should display 0.00 volts when the signal circuit is grounded to the ECM housing with a fused jumper wire. If the voltage displayed on the scan tool is more than the specified value, test the signal circuit of the BARO sensor for an open or a high resistance.
4. 9: The ECM produces a measurable steady-state amperage that provides the 5-volt reference to the BARO sensor. If the amperage on the 5-volt reference circuit is less than the specified value, test the 5-volt reference circuit for an open, a high resistance.
5. 10: This step tests for a high resistance in the low reference circuit of the BARO 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/TCM fuse allows the ECM to completely power down.

DTC P2227

The barometric pressure (BARO) sensor responds to changes in altitude and atmospheric conditions. This gives the engine control module (ECM) an indication of barometric pressure. The ECM uses this information to calculate fuel delivery. The BARO sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The ECM supplies 5 volts to the BARO sensor on a 5-volt reference circuit, and provides a ground on a low reference circuit. The BARO sensor provides a voltage signal to the ECM on a signal circuit relative to the atmospheric pressure changes. The ECM monitors the BARO sensor signal for a voltage outside of the normal range. If the ECM detects a BARO sensor signal voltage that is too low, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P2228 Barometric Pressure (BARO) Sensor Circuit Low Voltage

1. The engine is operating.
2. DTC P2228 runs continuously once the above conditions are met for 2 seconds.

1. The ECM detects that the BARO sensor voltage is less than 0.20 volts and the BARO pressure is less than 50 kPa.
2. The condition is 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.

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 lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/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 is testing the signal circuit. The signal circuit is pulled up to a voltage, so the scan tool should display a voltage within the specified range. If the voltage is low, this indicates the signal circuit is grounded.
3. 5: The ECM produces a measurable steady-state amperage that provides the 5-volt reference to the BARO sensor. If the amperage on the 5-volt reference circuit is less than the specified value, test the 5-volt reference circuit for an open, a high resistance, or for a short to ground.

DTC P2228

The barometric pressure (BARO) sensor responds to changes in altitude and atmospheric conditions. This gives the engine control module (ECM) an indication of barometric pressure. The ECM uses this information to calculate fuel delivery. The BARO sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The ECM supplies 5 volts to the BARO sensor on a 5-volt reference circuit, and provides a ground on a low reference circuit. The BARO sensor provides a voltage signal to the ECM on a signal circuit relative to the atmospheric pressure changes. The ECM monitors the BARO sensor signal for a voltage outside of the normal range. If the ECM detects a BARO sensor signal voltage that is too high, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P2229 Barometric Pressure (BARO) Sensor Circuit High Voltage

1. The engine is operating.
2. DTC P2229 runs continuously once the above conditions are met for 2 seconds.

1. The ECM detects that the BARO sensor voltage is more than 4.8 volts and the BARO pressure is more than 115 kPa.
2. The condition is 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.

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 lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/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 is present.
2. 4: This step is testing the signal circuit. The signal circuit is pulled-up to a voltage, so the DMM should display a voltage within the specified range. If the voltage is high, this indicates the signal circuit is shorted to a voltage. If the voltage is less than the specified range, test the signal circuit for an open.
3. 6: This step tests for high resistance in the low reference circuit of the BARO 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/TCM fuse allows the ECM to power down completely.

DTC P2229

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 DTCs

1. DTC P2231 HO2S Signal Circuit Shorted to Heater Circuit Bank 1 Sensor 1
2. DTC P2234 HO2S Signal Circuit Shorted to Heater Circuit Bank 2 Sensor 1

1. Before the ECM can report DTC P2231 or P2234 failed, DTC P0030, P0031, P0032, P0050, P0051, P0052, P0053, P0059, P0130, P0135, P0150, and P0155 must run and pass.
2. DTCs P0461, P0462, P0463, P2066, P2067, and P2068 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 10.5-18.0 volts.
9. The calculated exhaust temperature is less than 800°C (1,472°F).
10. The change in volumetric efficiency is less than 30 percent per second.
11. DTC P2231 and P2234 run continuously once the above conditions are met for more than 10 seconds when the fuel level is more than 12 percent.
12. DTC P2231 and P2234 run continuously once the above conditions are met for more than 10 minutes when the fuel level is less than 12 percent.

1. The ECM detects the internal HO2S voltage signal change is more than 100 mV as the heater control switches.
2. The above condition occurs 35 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.

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 lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. 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.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .
5. 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. 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.
3. 11: A rich or lean fuel injector can cause this DTC to set. Perform the «Fuel Injector Balance Test with Tech 2»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting) or the «Fuel Injector Balance Test with Special Tool»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting) to verify that the fuel injectors are delivering fuel equally. Replace any fuel injector that has a fuel pressure drop, or resistance measurement, that is not consistent in comparison to the other fuel injectors.

DTC P2231 or P2234

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 DTCs

1. DTC P2232 HO2S Signal Circuit Shorted to Heater Circuit Bank 1 Sensor 2
2. DTC P2235 HO2S Signal Circuit Shorted to Heater Circuit Bank 2 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 and P2235 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.

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 lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. 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.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/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 or P2235

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 DTCs

1. DTC P2237 HO2S Pumping Current Control Circuit Bank 1 Sensor 1
2. DTC P2240 HO2S Pumping Current Control Circuit Bank 2 Sensor 1

Conditions 1

1. Before the ECM can report DTC P2237 or P2240 failed, DTC P0101, P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336, and P0338 must run and pass.
2. DTCs P0030, P0031, P0032, P0050, P0051, P0052, P0133, P0135, P0153, and P0155 are not set.
3. The engine is operating in closed loop.
4. The ignition 1 voltage is between 10.7-18 volts.
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 and P2240 run continuously once the above conditions are met for approximately 8 seconds.

Conditions 2

1. Before the ECM can report DTC P2237 or P2240 failed, DTC 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 and P2240 run continuously once the above conditions are met for 1.5 seconds.

Conditions 3

1. The ignition 1 voltage is between 10.7-18 volts.
2. The HO2S heater is at operating temperature.
3. The ECM is commanding decel fuel cut-off for more than 3 seconds.
4. DTC P2237 and P2240 run continuously once the above conditions are met for more than 2 seconds.

Conditions 1

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.

Conditions 2

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.

Conditions 3

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 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.

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. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .
5. 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 input pump current and pump 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 or P2240

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 DTCs

1. DTC P2243 HO2S Reference Voltage Circuit Bank 1 Sensor 1
2. DTC P2247 HO2S Reference Voltage Circuit Bank 2 Sensor 1

1. Before the ECM can report DTC P2243 or P2247 failed, DTC P0030, P0031, P0032, P0050, P0051, and P0052 must run and pass.
2. The engine is operating for more than 2 seconds.
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 20 seconds.
6. DTC P2243 and P2247 run continuously once the above conditions are met.

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.

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. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .
5. 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. 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 P2243 or P2247

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 DTCs

1. DTC P2251 HO2S Reference Ground Circuit Bank 1 Sensor 1
2. DTC P2254 HO2S Reference Ground Circuit Bank 2 Sensor 1

1. Before the ECM can report DTC P2251 or P2254 failed, DTC P0030, P0031, P0032, P0050, P0051, and P0052 must run and pass.
2. The engine is operating.
3. The ignition 1 voltage is between 10-18 volts for more than 30 seconds.
4. The HO2S heater control is enabled.
5. The HO2S heater is at operating temperature for more than 20 seconds.
6. The calculated exhaust temperature is less than 900°C (1652°F).
7. The internal HO2S sensing element resistance is more than 570 ohms.
8. The ECM detects the internal HO2S signal voltage is between 1.47-1.53 volts.
9. A fuel cut-off event has not occurred in more than 2 seconds.
10. DTC P2251 and P2254 run continuously once the above conditions are met for 10 seconds.

1. The ECM detects the internal HO2S voltage signal change is more than 10 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.

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. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .
5. 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. 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 or P2254

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 test for the following conditions

1. The ECM monitors the HO2S 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 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 DTCs

1. DTC P2270 HO2S Signal Stuck Lean Bank 1 Sensor 2
2. DTC P2272 HO2S Signal Stuck Lean Bank 2 Sensor 2

1. Before the ECM can report DTC P2270 or P2272 failed, DTC P0036, P0037, P0038, P0056, P0057, P0058, P0137, P0138, P0140, P0141, P0157, P0158, P0160, P0161, P0341, P0342, P0343, P0346, P0347, P0348, P0366, P0367, P0368, P0391, P0392, P0393, P0443, P0458, and P0459 must run and pass.
2. DTCs P0461, P0462, P0463, P2066, P2067, and P2068 are not set.
3. The engine is operating.
4. The rear HO2S are 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 6-33 g/s for more than 3 seconds during the intrusive test.
8. DTC P2270 and P2272 runs continuously once the above conditions are met for approximately 10 minutes when the fuel level is more than 12 percent.
9. DTC P2270 and P2272 runs continuously once the above conditions are met for approximately 20 minutes when the fuel level is less 12 percent.

If the ECM detects that the rear HO2S voltage is less than 650 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 650 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.

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 lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. A fuel delivery condition causes this DTC to set. Thoroughly inspect all items that cause a lean condition.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/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.

DTC P2270 or P2272

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 test for the following conditions

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 DTCs

1. DTC P2271 HO2S Signal Stuck Rich Bank 1 Sensor 2
2. DTC P2273 HO2S Signal Stuck Rich Bank 2 Sensor 2

1. Before the ECM can report DTC P2270 or P2272 failed, DTC P0036, P0037, P0038, P0056, P0057, P0058, P0137, P0138, P0140, P0141, P0157, P0158, P0160, P0161, P0341, P0342, P0343, P0346, P0347, P0348, P0366, P0367, P0368, P0391, P0392, P0393, P0443, P0458, and P0459 must run and pass.
2. DTCs P0461, P0462, P0463, P2066, P2067, and P2068 are not set.
3. The engine is operating.
4. The rear HO2S are at operating temperature for more than 10 seconds.
5. The fuel injectors are enabled.
6. The long term fuel control is enabled.
7. The mass air flow (MAF) sensor is more than 10 g/s.
8. The MAF sensor is between 6-33 g/s for more than 3 seconds during the intrusive test.
9. The accumulated air flow into the engine is more than 15 grams during the fuel cut-off event.
10. DTC P2271 and P2273 runs continuously once the above conditions are met.

If the ECM detects that the rear HO2S voltage is more than 650 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 voltage is still more than 650 mV, the ECM then tests the HO2S at the next decel fuel cut-off. If the ECM detects the HO2S voltage is more than 200 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.

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 lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. A fuel delivery condition causes this DTC to set. Thoroughly inspect all items that cause a rich condition.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/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.

DTC P2271 or P2273

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 DTCs

1. DTC P2297 HO2S Performance During Decel Fuel Cut-Off (DFCO) Bank 1 Sensor 1
2. DTC P2298 HO2S Performance During Decel Fuel Cut-Off (DFCO) Bank 2 Sensor 1

Condition 1

1. Before the ECM can report DTC P2297 or P2298 failed, DTCs P0030, P0031, P0050, P0051, P0052, P0130, P0131, P0132, P0150, P0151, P0152, P2237, P2240, P2243, P2247, P2251, and P2254 must run and pass.
2. The engine is operating.
3. The front heated oxygen sensors are at operating temperature.
4. The desired front HO2S is less than 1.6 lambda.
5. The internal ECM HO2S signal voltage is less than 4.81 volts.
6. The fuel injectors are enabled.
7. DTC P2297 and P2298 runs continuously once the above conditions are met.

Condition 2

1. A decel fuel cut-off has occurred 10 times with successful adjustments.
2. DTC P2297 and P2298 runs continuously once the above conditions are met.

Condition 1

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

Condition 2

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 or P2298

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 ignition control 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 1400-5,000 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.

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 lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. Inspect the ignition coils for aftermarket devices. An aftermarket device connected to the ignition coil circuits, may cause this DTC to set.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers 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 ignition control 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 1400-5,000 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.

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 lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. Inspect the ignition coils for aftermarket devices. An aftermarket device connected to the ignition coil circuits may cause this DTC to set.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/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 voltage.

DTC P2301, P2304, P2307, P2310, P2313, or P2316

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 DTCs

1. DTC P2626 HO2S Pumping Current Trim Circuit Bank 1 Sensor 1
2. DTC P2629 HO2S Pumping Current Trim Circuit Bank 2 Sensor 1

1. Before the ECM can report DTC P2626 or P2629 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 10.7-18.0 volts.
4. The fuel system is in fuel shut-off.
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 and P2629 runs continuously once the above conditions are met.

1. The ECM internal HO2S voltage is more than 4.81 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.

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. The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-troubleshooting__intermittent-conditions) .
5. 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 or P2629

The fuel tank on this vehicle is equipped with 2 fuel level sensors, one for each reservoir of the fuel tank. Fuel is transferred from the left side of the fuel tank to the right side of the fuel tank in order to ensure all of the usable fuel volume is available. The fuel pump supplies a small amount of pressurized fuel to the siphon jet pump through the fuel feed pipe. The pressurized fuel creates a venturi action inside the siphon jet pump. The venturi action causes the fuel to be drawn out of the left side of the fuel tank. Fuel is then transferred from the left side of fuel tank to the right side of fuel tank through the internal fuel transfer tube.

This diagnostic tests for too large of a difference in fuel level between the left and right side of the fuel tank. If the control module determines that the right side fuel level is less than a predetermined amount of the left side fuel level, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P2636 Fuel Transfer Pump Flow Insufficient

1. Before the engine control module (ECM) can report DTC P2636 failed, DTCs P0462, P0463, P2067, and P2068 must run and pass.
2. The engine is operating.
3. DTC P2636 runs continuously once the above conditions exist for more than 4 minutes.

1. The ECM detects that the right side fuel level is less than 7.0 liters (1.8 gallons) and the left side fuel level is more than 15.0 liters (3.9 gallons).
2. The above condition is present for more than 2 minutes.

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 ECM commands the fuel gage to empty.
5. The driver information center displays Low Fuel.

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. 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 lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to «Engine Controls Component Views»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) .
3. Depending on the current fuel level, it may be difficult to locate a malfunctioning fuel level sensor. The condition may only occur when the fuel level is full or near empty. The fuel level sensor unit may need to be removed for further diagnosis. A fuel level sensor that has an intermittent condition causes this DTC to set. Remove the fuel level sensor. Refer to «Fuel Tank Module Replacement - Primary»(/cadillac/sts/i-2004-2007/remont/testing-diagnostics/#engine-control-system-36l-ly7-introduction) in order to test the resistance of the fuel level sensor. The resistance of the fuel level sensor should change between 40-250 ohms. Replace the sensor if the resistance did not change or was out of range.
4. For an intermittent condition, refer to «Intermittent Conditions»(/cadillac/sts/i-2004-2007/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 current.
2. 3: This step verifies possible component problems within the fuel tank.

P2636 Fuel Transfer Pump Flow Insufficient

The electronic brake control module (EBCM) sends antilock brake system (ABS) data to the engine control module (ECM). The data is sent to the ECM through a communication network called the GM local area network (LAN). Two circuits are used to communicate LAN data between the ECM and EBCM. A fault in the LAN will not cause DTC U0415 to set by itself. If a LAN fault occurs, other DTCs will set in addition to DTC U0415.

If the ECM receives invalid antilock brake system data from the EBCM, this DTC sets.

This diagnostic procedure supports the following DTC

DTC U0415 EBCM Communication Circuit Performance

1. The ignition is on for more than 3 seconds.
2. The ignition 1 voltage is between 10.5-18 volts.
3. No other communication errors are present.
4. DTC U0415 runs continuously once the above conditions are met.

The ECM receives no valid antilock brake system data from the EBCM for more than 1 second.

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.

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.

DTC U0415

The instrument panel module (IPM) sends cruise control data to the engine control module (ECM). The data is sent to the ECM through a communication network called the GM local area network (LAN). Two circuits are used to communicate LAN data between the ECM and IPM. A fault in the LAN will not cause DTC U0423 to set by itself. If a LAN fault occurs, other DTCs will set in addition to DTC U0423.

If the ECM receives invalid cruise control data from the IPM, this DTC sets.

This diagnostic procedure supports the following DTC

DTC U0423 IPM Communication Circuit Performance

1. The ignition is on for more than 3 seconds.
2. The ignition 1 voltage is between 10.5-18 volts.
3. No other communication errors are present.
4. DTC U0423 runs continuously once the above conditions are met.

The ECM receives no valid cruise control data from the IPM for more than 1 second.

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.

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.

DTC U0423

See also:
• Engine Controls Component Views
• Intermittent Conditions
• Engine Control Module (ECM) Connector End Views
• Engine Controls Connector End Views
• Diagnostic System Check - Vehicle
• Diagnostic Trouble Code (DTC) List - Vehicle
• Circuit Testing
• Wiring Repairs
• Symptoms - Engine Exhaust
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Control Module References
• DTC P0118
• Fuel Injector Balance Test with Tech 2
• Symptoms - Engine Mechanical
• Measuring Frequency
• Testing for Short to Ground
• Troubleshooting with a Test Lamp
• Lifting and Jacking the Vehicle
• Data Link Connector (DLC) Schematics
• ABS Connector End Views