Engine Controls - 2.6l & 3.2l - Diagnosis (DTC p2096 - p2636) Cadillac CTS I

Circuit Description

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the engine control module (ECM) operates in an open loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The ECM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage output indicates a rich fuel mixture; low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. Fuel Trim Biasing is used by the ECM to keep the post catalyst HO2S voltage as close to 600 mV as possible. This allows optimal catalyst efficiency. The ECM constantly monitors how long the Fuel Trim Bias is commanded lean or rich. If the ECM detects that the Fuel Trim Bias is commanded lean for longer than a calibrated amount of time DTC P2096 will set for Bank 1, or DTC P2098 will set for Bank 2

Conditions for Running the DTC

1. DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0101, P0102, P0103, P0116, P0117, P0118, P0125, P0128, P0135, P0141, P0155, P0161, P0171, P0172, P0174, P0175, P0300, P0301-P0306, P0313, P0341, P0342, P0343, P0420, P0430, P0443, P0444, or P0445 are not set.
2. The loop status parameter is closed.

Conditions for Setting the DTC

The ECM detects that the affected HO2S 1 fuel trim bias is commanded lean for longer than 1.3 seconds, within a 200 second monitoring period.

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 3 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. The most likely cause for this DTC is a deteriorated or contaminated HO2S 1.
2. Depending on the state of the HO2S deterioration, this code may not reset or may be very difficult to reset.
3. If the HO2S deterioration is significant enough, other HO2S DTCs may set or be present in concurrence with this DTC.
4. Attempt to compare the activity of both the affected bank HO2S 1 and HO2S 2 to the known good bank using the live plot feature of the scan tool. Operate the vehicle under various load and vehicle/engine speed conditions. Look for any indication of improper operation or contamination of the affected bank HO2S 1 or HO2S 2.
5. If an intermittent condition exists, refer to «Intermittent Conditions»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__intermittent-conditions) .

DTC P2096 or P2098

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the engine control module (ECM) operates in an open loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The ECM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage output indicates a rich fuel mixture; low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. Fuel Trim Biasing is used by the ECM to keep the post catalyst HO2S voltage as close to 600 mV as possible. This allows optimal catalyst efficiency. The ECM constantly monitors how long the Fuel Trim Bias is commanded lean or rich. If the ECM detects that the Fuel Trim Bias is commanded rich for longer than a calibrated amount of time, DTC P2097 will set for Bank 1 or DTC P2099 will set for Bank 2

1. DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0101, P0102, P0103, P0116, P0117, P0118, P0125, P0128, P0135, P0141, P0155, P0161, P0171, P0172, P0174, P0175, P0300, P0301-P0306, P0313, P0341, P0342, P0343, P0420, P0430, P0443, P0444, or P0445 are not set.
2. The loop status parameter is closed.

The ECM detects that the affected HO2S 1 fuel trim bias is commanded rich for longer than 1.3 seconds, within a 200 second monitoring period.

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 3 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 most likely cause for this DTC is a deteriorated or contaminated HO2S 1.
2. Depending on the state of HO2S deterioration, this code may not reset or may be very difficult to reset.
3. If the HO2S deterioration is significant enough, other HO2S DTCs may set or be present in concurrence with this DTC.
4. Attempt to compare the activity of both the affected bank HO2S 1 and HO2S 2 to the known good bank using the live plot feature of the scan tool. Operate the vehicle under various load and vehicle/engine speed conditions. Look for any indication of improper operation or contamination of the affected bank HO2S 1 or HO2S 2.
5. If an intermittent condition exists, refer to «Intermittent Conditions»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__intermittent-conditions) .

DTC P2097 or P2099

The engine control module (ECM) opens the throttle blades by applying a pulse width modulated voltage to the throttle valve motor. The ECM reverses the polarity on the throttle valve motor control circuits in order to close the throttle blades. The ECM increases the pulse width as necessary to open the throttle blades. The ECM monitors throttle position (TP) sensors 1 and 2 to determine the actual blade position. If the ECM detects the required pulse width modulation to move the throttle valves exceeds a predetermined value, DTC 2100 sets.

1. The ignition is ON.
2. The engine coolant temperature (ECT) is 5-100°C (41-212°F).
3. The intake air temperature (IAT) is more than 5°C (41°F).
4. The battery voltage is more than 10 volts.

The control module determines that PWM to move the throttle blades exceeds a predetermined value.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 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. Inspect for a condition in which the throttle valves may have been held open.
2. Inspect for conditions in which ice may have formed in the throttle bore.
3. The throttle valves are spring loaded to a slightly open position.
4. The throttle valves should be open approximately 3-5 percent. This is referred to as the rest position.
5. The throttle valves should not be completely closed, nor should they be open any more than the specified amount.
6. The throttle valves should move open and to the closed position without binding under the normal spring pressure.
7. The throttle should NOT be free to move open or closed WITHOUT spring pressure.
8. The scan tool has the ability to operate the throttle control system using the Throttle Position function located in the TAC System menu. This function will operate the throttle valve through the entire range in order to determine if the throttle body and system operate correctly.
9. If the condition is intermittent, refer to «Intermittent Conditions»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__intermittent-conditions) .

Test Description

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

1. 3: The throttle valves are spring loaded in a slightly open position and should move in either direction without binding. The throttle valves should always be under spring pressure.
2. 6: When the ignition is turned ON, the ECM operates the throttle control motor to verify the integrity of the system prior to start-up. This can be seen by the momentary flash of the test lamp as the ignition is turned ON.

DTC P2100

The engine control module (ECM) controls the throttle blades by applying a varying voltage to the throttle valve motor. The ECM monitors the actual throttle blade position using throttle position (TP) sensor 1 and 2. If the ECM cannot detect the minimum throttle position, DTC P2101 sets.

The ignition is ON.

The difference between the calculated and the actual throttle position is more than a predetermined value.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 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 throttle valves are spring loaded to a slightly open position. The throttle valves should be open approximately 3-5 percent. This is referred to as the rest position. The throttle valves should not be completely closed, nor should they be open any more than the specified amount. The throttle valves should move open and to the closed position without binding under the normal spring pressure. The throttle should NOT be free to move open or closed WITHOUT spring pressure.
2. The scan tool has the ability to operate the throttle control system using Special Functions. Actuate the throttle valves using the Throttle Position function located in the TAC system menu. This function will operate the throttle valve through the entire range in order to determine if the throttle body and system operate correctly.
3. For intermittent conditions, refer to «Intermittent Conditions»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__intermittent-conditions) .

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

1. 4: The throttle valves are spring loaded in a slightly open position and should move in either direction without binding. The throttle valves should always be under spring pressure.
2. 7: When the ignition is turned ON, the ECM operates the throttle control motor to verify the integrity of the system prior to start-up. This can be seen by the momentary flash of the test lamp as the ignition is turned ON.

DTC P2101

The engine control module (ECM) controls the throttle blades by applying a varying voltage to the throttle valve motor. The ECM monitors the actual throttle blade position using the throttle position (TP) sensor 1 and 2. If the ECM detects the throttle actuator control system does not operate in the desired throttle range, DTC P2107 sets.

1. The ignition is ON.
2. The vehicle speed is 0 km/h (0 mph).
3. The engine speed is less than 50 RPM.
4. The engine coolant temperature (ECT) is 5-100°C (41-212°F).
5. The intake air temperature (IAT) is more than 5°C (41°F).
6. The battery voltage is more than 10 volts.
7. The accelerator pedal position (APP) is less than 15 percent.

The ECM determines that the system is outside the calibrated range.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 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. Inspect for a condition in which the throttle valves may have been held open.
2. Inspect for conditions in which ice may have formed in the throttle bore.
3. The throttle valves are spring loaded to a slightly open position. The throttle valves should be open approximately 3-5 percent. This is referred to as the rest position. The throttle valves should not be completely closed, nor should they be open any more than the specified amount. The throttle valves should move open and to the closed position without binding under the normal spring pressure. The throttle should NOT be free to move open or closed WITHOUT spring pressure.
4. The scan tool has the ability to operate the throttle control system using the Throttle Position function located in the TAC system menu. This function will operate the throttle valve through the entire range in order to determine if the throttle body and system operate correctly.
5. For intermittent conditions, refer to «Intermittent Conditions»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__intermittent-conditions) for the intermittents.

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

1. 4: The throttle valves are spring loaded in a slightly open position and should move in either direction without binding. The throttle valves should always be under spring pressure.
2. 7: When the ignition is turned ON, the ECM operates the throttle control motor to verify the integrity of the system prior to start-up. This can be seen by the momentary flash of the test lamp as the ignition is turned ON.

DTC P2107

DTC P2110

If the engine control module (ECM) detects a condition in the throttle actuator control (TAC) system, the ECM disables the TAC motor. The accelerator pedal position (APP) sensor will have no affect on the throttle position and the throttle will remain in the rest position. The RPM will vary due to limited fuel and spark changes based on APP input. If the engine speed is above 1,300 RPM, the ECM will turn the fuel off for short intervals until the engine RPM is below 1,300 RPM. If the ECM detects a fault in the TAC system that is beyond its controllable limits, DTC P2110 sets.

The engine is running.

1. The ECM detects an error in the throttle actuator control system.
2. The engine speed is more than 1,120 RPM.
3. The condition exists for longer than 5 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
3. The control module will cause the engine to turn OFF.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 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.

DTC P2110

The engine control module (ECM) controls the throttle blades by applying a varying voltage to the throttle valve motor. The ECM monitors the actual throttle blade position using throttle position (TP) sensor 1 and 2. If the ECM detects the throttle blade did not return to the rest position within a calibrated time, DTC P2119 sets.

1. The ignition is ON.
2. The vehicle speed is 0 km/h (0 mph).
3. The engine speed is less than 250 RPM.
4. The engine coolant temperature (ECT) is 5-100°C (41-212°F).
5. The intake air temperature (IAT) is more than 5°C (41°F).
6. The battery voltage is more than 10 volts.
7. The accelerator pedal position (APP) is less than 15 percent.

The control module determines that the throttle valves are not in the closed position.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 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. Inspect for a condition in which the throttle valves may have been held open.
2. Inspect for conditions in which ice may have formed in the throttle bore.
3. The throttle valves are spring loaded to a slightly open position. The throttle valves should be open approximately 3-5 percent. This is referred to as the rest position. The throttle valves should not be completely closed, nor should they be open any more than the specified amount. The throttle valves should move open and to the closed position without binding under the normal spring pressure. The throttle should NOT be free to move open or closed WITHOUT spring pressure.
4. The scan tool has the ability to operate the throttle control system using the Throttle Position function located in the TAC system menu. This function will operate the throttle valve through the entire range in order to determine if the throttle body and system operate correctly.
5. For intermittent conditions, refer to «Intermittent Conditions»(/cadillac/cts/i-2002-2007/remont/testing-diagnostics/#engine-controls-26l-32l-troubleshooting__intermittent-conditions) .

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

1. 3: The throttle valves are spring loaded in a slightly open position and should move in either direction without binding. The throttle valves should always be under spring pressure.
2. 6: When the ignition is turned ON, the ECM operates the throttle control motor to verify the integrity of the system prior to start-up. This can be seen by the momentary flash of the test lamp as the ignition is turned ON.

DTC P2119

The accelerator pedal position (APP) sensor is made up of 2 sensors that are housed inside one assembly. The engine control module (ECM) supplies a separate 5-volt reference and the low reference circuit for each of the sensors. The 5-volt reference for APP sensor 1 is supplied from the same source in the ECM as the 5-volt reference for the mass air flow (MAF) sensor and the fuel tank pressure (FTP) sensor. The 5-volt reference voltage for all of the sensors is supplied on separate ECM terminals, but the terminals are connected internally to a voltage supply. The APP sensor 1 sends a signal from the sensor to the ECM indicating the accelerator pedal position. The ECM actuates the throttle plates based on this information. The APP sensor 1 signal voltage increases as the pedal is depressed, from approximately 0.8 volts at rest to above 3.5 volts fully depressed. If the ECM detects that the signal voltage is excessively low, DTC P2122 sets.

1. The battery voltage is more than 10 volts.
2. The accelerator pedal is not in the rest position.

The APP sensor 1 voltage is less than 0.84 volts for more than 140 milliseconds.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 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.

Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems for intermittent conditions.

DTC P2122

The accelerator pedal position (APP) sensor is made up of 2 sensors that are housed inside one assembly. The engine control module (ECM) supplies a separate 5-volt reference and low reference circuit for each of the sensors. The 5-volt reference for APP sensor 1 is supplied from the same source in the ECM as the 5-volt reference for the mass air flow (MAF) sensor and the fuel tank pressure (FTP) sensor. The 5-volt reference voltage for all of the sensors is supplied on separate ECM terminals, but the terminals are connected internally to a voltage supply. The APP sensor 1 sends a signal from the sensor to the ECM indicating the accelerator pedal position. The ECM actuates the throttle plates based on this information. The APP sensor 1 signal voltage increases as the pedal is depressed, from approximately 0.8 volts at rest to above 3.5 volts when fully depressed. If the ECM detects that the signal voltage is excessively high, DTC P2123 sets.

1. The ignition is ON.
2. The battery voltage is more than 10 volts.
3. The accelerator pedal is not in the rest position.

The APP sensor 1 voltage is more than 4.8 volts for more than 140 milliseconds.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 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.

DTC P2123

The accelerator pedal position (APP) sensor is made up of 2 sensors that are housed inside one assembly. The engine control module (ECM) supplies a separate 5-volt reference and the low reference circuit for each of the sensors. The 5-volt reference for the APP sensor 2 is supplied from the same source in the ECM as the 5-volt reference of the throttle position (TP) sensors. The 5-volt reference voltage for all of the sensors is supplied on separate ECM terminals, but the terminals are connected internally to a voltage supply. The APP sensor 2 sends a signal indicating the accelerator pedal position and the ECM actuates the throttle plates based on this information. The APP sensor 2 signal voltage increases from about 0.2 volts at rest to about 1.8 volts fully depressed. If the ECM detects that the signal voltage is excessively low, DTC P2127 sets.

1. The ignition is ON.
2. The battery voltage is more than 10 volts.
3. The accelerator pedal is not in the rest position.

The APP sensor 2 voltage is less than 0.66 volts for more than 140 milliseconds.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 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.

DTC P2127

The accelerator pedal position (APP) sensor is made up of 2 sensors that are housed inside one assembly. The engine control module (ECM) supplies a separate 5-volt reference and low reference circuit for each of the sensors. The 5-volt reference for the APP sensor 2 is supplied from the same source in the ECM as the 5-volt reference for the throttle position sensors. The 5-volt reference voltage for all of the sensors is supplied on separate ECM terminals, but the terminals are connected internally to a voltage supply. The APP sensor 2 sends a signal indicating the accelerator pedal position and the ECM actuates the throttle plates based on this information. The APP sensor 2 signal voltage increases from about 0.2 volts at rest to about 1.8 volts when fully depressed. If the ECM detects that the signal voltage is excessively high, DTC P2128 sets.

1. The ignition is ON.
2. The battery voltage is more than 10 volts.
3. The accelerator pedal is not in the rest position.

The APP sensor 2 voltage is more than 4.6 volts for more than 140 milliseconds.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 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.

DTC P2128

The throttle position (TP) sensors 1 and 2 are located within the throttle body assembly. The TP sensors share a common 5-volt reference circuit and a common low reference circuit. The 5-volt reference circuit is also shared with accelerator pedal position (APP) sensor 2. The 5-volt reference voltage is supplied on 2 separate engine control module (ECM) terminals, but the terminals are connected internally to the same voltage supply. Each TP sensor has an individual signal circuit, which provides the ECM with a signal voltage proportional to throttle the plate movement. When the throttle plate is in the closed position, the TP sensor 1 signal voltage is near the low reference and increases as the throttle plate is opened. The TP sensor 2 signal voltage at closed throttle is near the 5-volt reference and decreases as the throttle plate is opened. The ECM compares the signal of the throttle position sensors to the predicted TP sensor signal, based on calculations from the mass air flow (MAF) sensor. The control module also compares the signal of the TP sensor 1 and TP sensor 2 through the entire range. If the ECM detects a difference from the predicted range of more than 6 percent between sensor 1 and sensor 2, DTC P2135 sets.

1. The battery voltage is more than 10 volts.
2. The ignition is ON.

The ECM detects that the difference between TP sensor 1 and TP sensor 2 is more than the predicted value.

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

Conditions for Clearing the DTC

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

DTC P2135

The accelerator pedal position (APP) sensor is made up of 2 sensors that are housed inside one assembly. The engine control module (ECM) supplies a separate 5-volt reference and low reference circuit for each of the sensors. The 5-volt reference for APP sensor 1 is supplied from the same source in the ECM as the 5-volt reference for the mass air flow (MAF) sensor and the fuel tank pressure (FTP) sensor. The 5-volt reference for APP sensor 2 is supplied from the same source in the ECM as the 5-volt reference for the throttle position (TP) sensors. The 5-volt reference voltage for all of the sensors is supplied on separate ECM terminals, but the terminals are connected internally to the shared voltage supply. The APP sensor sends a signal from each of the sensors to the ECM indicating the accelerator pedal position. The ECM actuates the throttle plates based on this information. The APP sensor 1 signal voltage increases as the throttle opens, from about 0.4 volts at closed throttle to above 3.5 volts at wide-open throttle (WOT). The APP sensor 2 signal voltage also increases as the throttle opens, but at a slightly different rate. The APP sensor 2 signal voltage increases from about 0.2 volts at closed throttle to about 1.8 volts at WOT. The control module compares the signal of each of the APP sensors, when the pedal is not in the rest position. If the ECM detects the APP sensors are not within a predicted value from each other, DTC P2138 sets.

1. The battery voltage is more than 10 volts.
2. The ignition is ON.
3. The accelerator pedal is not in the rest position.

The ECM detects that the difference between APP sensor 1 and APP sensor 2 is more than the predicted value.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 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.

DTC P2138

The engine control module (ECM) controls the throttle blades by applying a varying voltage to the throttle valve motor. The ECM monitors the actual throttle blade position using throttle position (TP) sensor 1 and 2. If the ECM cannot detect the minimum throttle position, DTC P2176 sets.

1. The vehicle speed is 0 km/h (0 mph).
2. The engine speed is less than 40 RPM.
3. The engine coolant temperature (ECT) is between 5-85°C (41-185°F).
4. The intake air temperature (IAT) is less than 50°C (122°F).
5. The battery voltage is more than 10 volts.
6. The accelerator pedal position (APP) is less than 15 percent.

The control module can not determine the minimum throttle position.

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 3 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. Inspect for a condition in which the throttle valves may be held open.
2. Inspect for conditions in which ice may have formed in the throttle bore.

The throttle valves are spring loaded to a slightly open position. The throttle valves should be open approximately 3-5 percent. This is referred to as the rest position. The throttle valves should not be completely closed, nor should they be open any more than the specified amount. The throttle valves should move open and to the closed position without binding under the normal spring pressure. The throttle should NOT be free to move open or closed WITHOUT spring pressure.

The scan tool has the ability to operate the throttle control system using Special Functions. Actuate the throttle valves using the Throttle Position function located in the TAC system menu. This function will operate the throttle valve through the entire range in order to determine if the throttle body and system operate correctly.

For intermittent conditions, refer to Intermittent Conditions .

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

1. 4: The throttle valves are spring loaded in a slightly open position and should move in either direction without binding. The throttle valves should always be under spring pressure.
2. 7: When the ignition is turned ON, the ECM operates the throttle control motor to verify the integrity of the system prior to start-up. This can be seen by the momentary flash of the test lamp as the ignition is turned ON.

DTC P2176

The right fuel level sensor measures fuel level changes within the right fuel tank. When the fuel level is high the sensor signal voltage is high. When the fuel level is low the sensor signal voltage is low. The control module uses inputs from the left fuel level sensor and the right fuel level sensor in order to calculate the total fuel remaining in both sides of the fuel tank. The control module sends this information via class 2 to the instrument panel cluster.

This diagnostic tests for a restriction in the fuel system between the left and right of the fuel tank. If the control module determines that the fuel level, secondary side of tank, signal appears to be stuck based on a lack of signal variation expected during normal operation, this DTC sets.

The fuel pump also 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.

The fuel level in the fuel tank will equalize when the following occur

1. The electric fuel pump is operating.
2. The fuel level is more than 50 percent.
3. The vehicle is being re-fueled.

The engine is running.

1. The engine control module (ECM) does not detect a difference of at least 3.7 liters (1 gallon) between the fuel level 1 and fuel level 2 sending units.
2. Engine operating 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 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.

Depending on the current fuel level, it may be difficult to locate a malfunctioning sending unit. The malfunction may only occur when the fuel level is full or near empty. The fuel sending 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 or Fuel Tank Module Replacement - Secondary in order to test the resistance of the sensors. The resistance of the sensor should change between 40-250 ohms. Replace the sensor if the resistance did not change or was out of range.

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

1. 2: This step determines if a condition current.
2. 4: This step verifies possible component problems within the fuel tank.

DTC P2636

See also:
• Intermittent Conditions
• Engine Controls Schematics
• Engine Controls Connector End Views
• Engine Control Module (ECM) Connector End Views
• Diagnostic System Check - Engine Controls
• DTC P0134 or P0154
• Diagnostic Trouble Code (DTC) List
• Circuit Testing
• Wiring Repairs
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Engine Control Module (ECM) Replacement
• Idle Learn Procedure
• Fuel Tank Replacement
• Power and Grounding Component Views