Engine Controls - 2.0l (DTC p1680 to p2229) Chevrolet Cobalt I

Circuit Description

The throttle actuator control (TAC) system uses 2 accelerator pedal position (APP) sensors to monitor the pedal position. Two processors are also used to monitor the TAC system data. The powertrain control module (PCM) performs an intrusive test in order to detect that the APP signals are not shorted together. The PCM accomplishes this by pulling the APP sensor 2 low momentarily and looking for sensor 1 to also be low. The TAC system also performs this test on the throttle position (TP) sensors. This diagnostic monitors the transistor used to pull one pedal and one throttle sensor to ground simultaneously. Additionally, Both processors monitor each other's data to verify that the indicated APP calculation is correct.

If the transistor does not toggle within a calibrated period, or the indicated APP calculation is incorrect, DTC P1680 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC P1680 Control Module Accelerator Pedal Position (APP) System Performance

Conditions for Running the DTC

1. The system voltage is more than 5.23 volts.
2. The ignition is in Unlock/Accessory or Run position.
3. DTCs P0601, P0602, P0604, P0606, P0607, or P1621 are not set.
4. DTC P1680 runs continuously when the above conditions are met.

Conditions for Setting the DTC

1. The APP sensor 2 voltage is more than 2.05 volts for more than 0.3 second during the intrusive test. OR
2. The APP sensor calculations in the main processor differ from the motor control processor by more than 0.142 volt for more than 1.2 seconds.

Action Taken When the DTC Sets

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 and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

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.

Test Description

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

1. 2: A DTC P0602 indicates that the PCM is not programmed.
2. 5: Resistance is measured at the pedal assembly because a pedal resistance that is lower than the specified value will set this DTC.

DTC P1680

The Throttle Actuator Control (TAC) System determines the drivers intent and then calculates the appropriate throttle response. The TAC system achieves throttle positioning by providing a pulse width modulated voltage to the TAC motor. The powertrain control module (PCM) is the control center for the TAC system. Ignition 1 voltage is supplied on 2 separate circuits to the PCM. If the PCM detects a voltage difference between the 2 circuits, DTC P1682 sets.

This diagnostic procedure supports the following DTC

DTC P1682 Ignition 1 Switch Circuit 2

1. The ignition is in Unlock, Accessory, Run, or Crank mode.
2. DTC P1682 runs continuously when the above condition is met.

The ignition 1 voltage is less than 10 volts for more than 10 seconds.

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

Conditions for Clearing the DTC

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

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

1. 3: This step determines if there is voltage present to the ECM fuse.
2. 5: This step determines if voltage is present at the PCM.
3. 6: This step determines if the PCM ignition 1 voltage circuit is shorted to ground.

DTC P1682

The commanded throttle position is compared to the actual throttle position based on accelerator pedal position and possibly other limiting factors. Both values should be within a calibrated range of each other. The powertrain control module (PCM) continuously monitors the commanded and actual throttle positions. This DTC sets if the values are greater than the calibrated range.

This diagnostic procedure supports the following DTC

DTC P2101 Throttle Actuator Position Performance

1. The ignition is in the Run or Crank position.
2. The ignition voltage is greater than 8 volts.
3. The system is not in Battery Saver mode.
4. The engine is running.
5. DTC P0068 is not set.
6. DTC P2101 runs continuously when the above conditions are met.

The difference between the predicted and the actual throttle position is more than a calibrated amount for more than 0.2 second.

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 and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

1. The PCM turns OFF the MIL after 3 consecutive drive trips that the diagnostic runs and passes.
2. A History DTC clears after 40 consecutive warm-up cycles in which there are no failures reported of this diagnostic or any other emission related diagnostic.
3. The scan tool clears the MIL/DTC.

Diagnostic Aids

1. The throttle valve is spring loaded to a slightly open position. This is referred to as the rest position.
2. The throttle valve should not be completely closed nor should they be open any more than the specified amount.
3. The throttle valve should move open and to the closed position without binding under the normal spring pressure.
4. The throttle should NOT be free to move open or closed WITHOUT spring pressure. Replace the throttle body if any of these conditions are found.
5. The scan tool has the ability to operate the throttle control system using Special Functions. Actuate the throttle valve using the throttle blade control 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.
6. Inspect for the following conditions: Use the J 35616 Connector Test Adapter Kit for any test that requires probing the PCM harness connector or a component harness connector. Poor connections at the PCM or at the component-Inspect the harness connectors for a poor terminal to wire connection. Refer to «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cobalt/i-2004-2010/remont/electrical-component-locations/#wiring-systems-electrical-power-management__testing-for-intermittent-conditions-and-poor) in Wiring Systems for the proper procedure.
7. If the condition is intermittent, refer to «Intermittent Conditions»(/chevrolet/cobalt/i-2004-2010/remont/testing-diagnostics/#engine-controls-20l-troubleshooting-diagnosis__intermittent-conditions) .

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

1. 8: The throttle valve is spring loaded in a slightly open position and should move in either direction without binding. The throttle valve should always be under spring pressure.
2. 11: When the ignition is turned ON, the PCM 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

During Battery Saver mode, the powertrain control module (PCM) determines if the throttle plate is returning to the correct de-energized position. If the PCM determines the throttle plate is not at the correct position during battery saver mode, this DTC is set.

This diagnostic procedure supports the following DTC

DTC P2119 Throttle Closed Position Performance

1. The ignition is ON, and the engine is OFF.
2. The ignition voltage is more than 8.5 volts.
3. The battery Saver mode is active.
4. DTC P2119 runs continuously once each time the above conditions are met.

The PCM detects that the commanded and the actual throttle positions are not within a calibrated range of each other.

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

1. The DTC becomes history when the conditions for setting the DTC are no longer present.
2. The history DTC clears after 40 malfunction free warm-up cycles.
3. The PCM receives a clear code command from the scan tool.

1. Inspect for mechanical conditions or binding that may be temperature related.
2. Components may not move freely in extreme heat or cold due to the presence of contaminants or ice formation.

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

1. 8: More than one ETC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Keep this in mind when reviewing captured DTC info.

DTC P2119

The accelerator pedal position (APP) sensors 1 and 2 are located within the accelerator pedal assembly. Each sensor has the following circuits

1. A 5-volt reference circuit
2. A low reference circuit
3. A signal circuit

This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated. When APP sensor 1 signal voltage is not within the predicted range, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P2120 Accelerator Pedal Position (APP) Sensor 1 Circuit

1. The ignition switch is in the Unlock, Accessory, Run or Crank position.
2. The ignition voltage is greater than 5.23 volts.
3. DTCs P0641, P2122, P2123 are not set.
4. DTC P2120 runs continuously when the above conditions are met.

The APP sensor 1 voltage is less than 0.75 volt or more than 4.65 volts for more than 0.5 second.

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 and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine 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 P2120

The accelerator pedal position (APP) sensor 1 and sensor 2 are located within the accelerator pedal assembly. Each sensor has the following circuits

1. A 5-volt reference
2. A low reference
3. A signal

This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated. If the PCM detects the APP sensor 1 signal voltage is not within the predicted range, DTC P2122 sets.

This diagnostic procedure supports the following DTC

DTC P2122 Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage

1. The ignition switch is in the Unlock, Accessory, Run, or Crank position.
2. The ignition voltage is more than 5.23 volts.
3. DTC P0641 is not set.
4. DTC P2122 runs continuously when the above conditions are met.

The PCM detects that the APP sensor 1 voltage is less than 0.75 volt for more than 0.4 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 and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine 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 P2122

The accelerator pedal position (APP) sensor 1 and sensor 2 are located within the accelerator pedal assembly. Each sensor has the following circuits

1. A 5-volt reference
2. A low reference
3. A signal

This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated. If the PCM detects the APP sensor 1 signal voltage is not within the predicted range, DTC P2123 sets.

This diagnostic procedure supports the following DTC

DTC P2123 Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage

1. The ignition switch is in the Unlock, Accessory, Run, or Crank position.
2. The ignition voltage is more than 5.23 volts.
3. DTC P0641 is not set.
4. DTC P2123 runs continuously when the above conditions are met.

The PCM detects that the APP sensor 1 voltage is more than 4.65 volts for more than 0.4 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 and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine 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 P2123

The accelerator pedal position (APP) sensors 1 and 2 are located within the accelerator pedal assembly. Each sensor has the following circuits

1. A 5-volt reference circuit
2. A low reference circuit
3. A signal circuit

This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated. When APP sensor 2 signal voltage is not within the predicted range, this DTC sets.

This diagnostic procedure supports the following DTC

DTC P2125 Accelerator Pedal Position (APP) Sensor 2 Circuit

1. The ignition switch is in the Unlock, Accessory, Run, or Crank position.
2. The ignition voltage is greater than 5.23 volts.
3. DTCs P0641, P2127, P2128 are not set.
4. DTC P2125 runs continuously when the above conditions are met.

The APP sensor 2 voltage is less than 0.75 volt or more than 4.65 volts for more than 0.5 second.

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 and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine 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 P2125

The accelerator pedal position (APP) sensor 1 and sensor 2 are located within the accelerator pedal assembly. Each sensor has the following circuits

1. A 5-volt reference circuit
2. A low reference circuit
3. A signal circuit

This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated. If the PCM detects that the APP sensor 2 signal voltage is not within the predicted range, DTC P2127 sets.

This diagnostic procedure supports the following DTC

DTC P2127 Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage

1. The ignition is ON.
2. The ignition voltage is more than 5.23 volts.
3. DTC P0641 is not set.
4. DTC P2127 runs continuously when the above conditions are met.

The PCM detects that the APP sensor 2 voltage is less than 0.75 volt for more than 0.4 second.

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 and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine 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 P2127

The accelerator pedal position (APP) sensor 1 and sensor 2 are located within the accelerator pedal assembly. Each sensor has the following circuits

1. A 5-volt reference circuit
2. A low reference circuit
3. A signal circuit

This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated. If the PCM detects that the APP sensor 2 signal voltage is not within the predicted range, DTC P2128 sets.

This diagnostic procedure supports the following DTC

DTC P2128 Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage

1. The ignition switch is in the Unlock, Accessory, Run, or Crank position.
2. The ignition voltage is more than 5.23 volts.
3. DTC P0641 is not set.
4. DTC P2128 runs continuously when the above conditions are met.

The PCM detects that the APP sensor 2 voltage is more than 4.65 volts for more than 0.4 second.

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 and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine 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 P2128

The throttle actuator control assembly has two throttle position (TP) sensors mounted within the assembly. The powertrain control module (PCM) provides individual signal, ground, and 5-volt reference circuits to each sensor. When the throttle is opened from 0-100 percent, one sensor signal voltage increases while the other decreases. The signal circuit for TP sensor 1 is referenced to ground, and the signal circuit for TP sensor 2 is pulled up to 5 volts within the PCM.

This diagnostic procedure supports the following DTC

DTC P2135 Throttle Position (TP) Sensor 1-2 Correlation

1. The ignition switch is in the Unlock, Accessory, Run, or Crank position.
2. DTCs P0120, P0220, P0641, or P0651 are not set.
3. The ignition voltage is greater than 5.23 volts.
4. DTC P2135 runs continuously when the above conditions are met.

The difference between the TP sensor 1 and TP sensor 2 exceeds a predetermined value for more than 0.4 second.

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 and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

1. The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed.
2. The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
3. The DTC can be cleared by using a scan tool.

If the DTC is determined to be intermittent, refer to Intermittent Conditions .

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

1. 6: This step tests the integrity of the 5-volt reference and ground circuits of the TP sensors.
2. 7: This step determines if the 5-volt reference circuit or the sensor ground circuit is the cause of the DTC.
3. 8: If the scan tool displays 100 percent for the TP sensor 1 and the TP sensor 2 angle, this indicates that the TP sensor signal circuits are not the cause of the DTC.
4. 9: This step tests for excessive resistance in the TP sensor 5-volt reference circuit between the TP sensor harness connector and the PCM harness connector.
5. 10: This step tests for excessive resistance in the TP sensor ground circuit between the TP sensor harness connector and the PCM harness connector.
6. 11: This step tests for the TP sensor signal circuits for being shorted to another circuit in the PCM wiring harness between the PCM and the TP sensor wiring harness.
7. 16: When the PCM detects a problem within the throttle control system, more than one related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual problem may correct more than one DTC. Keep this in mind when reviewing captured DTC info.

DTC P2135

The accelerator pedal position (APP) sensors 1 and 2 are located within the accelerator pedal assembly. Each sensor has the following circuits

1. A 5-volt reference circuit
2. A low reference circuit
3. A signal circuit

This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated.

This diagnostic procedure supports the following DTC

DTC P2138 Accelerator Pedal Position (APP) Sensor 1-2 Correlation

1. The battery voltage is more than 5.23 volts.
2. DTCs P0641, P0651, P2120, or P2125, are not set.
3. DTC P2138 runs continuously when the above conditions are met.

The voltage difference between APP sensor 1 and APP sensor 2 exceeds a predetermined value for more than 0.5 second.

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 and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

1. The PCM turns OFF the MIL after 3 consecutive drive trips that the diagnostic runs and does not fail.
2. A History DTC clears after 40 consecutive warm up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.
3. The scan tool clears the MIL/DTC.

1. The PCM compares the signal of each of the accelerator pedal position sensor to each other throughout the entire range of operation. Clear the DTCs and actuate the pedal through the entire range with the ignition ON and the engine OFF.
2. Use the J 35616 Connector Test Adapter Kit for any test that requires probing the PCM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.
3. Refer to «Intermittent Conditions»(/chevrolet/cobalt/i-2004-2010/remont/testing-diagnostics/#engine-controls-20l-troubleshooting-diagnosis__intermittent-conditions) for intermittent conditions.

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

1. 2: Any circuit faults on either APP sensor 1 or 2 will set one of the DTCs listed. Refer to the appropriate table for diagnosis.

DTC P2138

The commanded throttle position is compared to the actual throttle position based on accelerator pedal position and possibly other limiting factors. Both values should be within a calibrated range of each other. The powertrain control module (PCM) continuously monitors the commanded and actual throttle positions. This DTC sets if the values are greater than the calibrated range.

This diagnostic procedure supports the following DTC

DTC P2176 Minimum Throttle Position Not Learned

1. DTCs P0120, P0121, P0122, P0123, P0220, P0222, P0223, P1516, P2135 are not met.
2. The minimum learn procedure is active.
3. The throttle position is steady.
4. The ignition switch is in the Run or Crank position.
5. DTC P2176 runs continuously when the above conditions are met.

The difference between the predicted and the actual throttle position is more than a calibrated amount for more than 3 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 and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. A message center or an indicator displays Reduced Engine Power.
5. Under certain conditions the control module commands the engine OFF.

1. The PCM turns OFF the MIL after 3 consecutive drive trips that the diagnostic runs and passes.
2. A History DTC clears after 40 consecutive warm-up cycles in which there are no failures reported of this diagnostic or any other emission related diagnostic.
3. The scan tool clears the MIL/DTC.

1. The throttle valve is spring loaded to a slightly open position.
2. The throttle valve should be open approximately 20 percent. This is referred to as the rest position.
3. The throttle valve should not be completely closed nor should they be open any more than the specified amount.
4. The throttle valve should move open and to the closed position without binding under the normal spring pressure.
5. The throttle should NOT be free to move open or closed WITHOUT spring pressure. Replace the throttle body if any of these conditions are found.
6. The scan tool has the ability to operate the throttle control system using Special Functions. Actuate the throttle valve using the throttle blade control 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.
7. Inspect for the following conditions: Use the J 35616 Connector Test Adapter Kit for any test that requires probing the PCM harness connector or a component harness connector. Poor connections at the PCM or at the component-Inspect the harness connectors for a poor terminal to wire connection. Refer to «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/cobalt/i-2004-2010/remont/electrical-component-locations/#wiring-systems-electrical-power-management__testing-for-intermittent-conditions-and-poor) in Wiring Systems for the proper procedure. If the condition is intermittent, refer to «Intermittent Conditions»(/chevrolet/cobalt/i-2004-2010/remont/testing-diagnostics/#engine-controls-20l-troubleshooting-diagnosis__intermittent-conditions) .

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

1. 8: The throttle valve is spring loaded in a slightly open position and should move in either direction without binding. The throttle valve should always be under spring pressure.
2. 11: When the ignition is turned ON, the PCM 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 barometric pressure (BARO) sensor is a transducer that varies resistance according to changes in altitude and atmospheric conditions. This gives the powertrain control module (PCM) an indication of the current barometric pressure. The PCM 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 PCM 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 PCM on a signal circuit relative to the pressure changes. The PCM monitors the stability of the BARO sensor output by comparing successive samples. If the PCM detects that the difference between the samples is more than a predetermined amount, DTC P2227 sets.

This diagnostic procedure supports the following DTC

DTC P2227 Barometric Pressure (BARO) Sensor Performance

1. DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0120, P0125, P0128, P0220, P0502, P0503, P0506, P0507, P1182, P1183, P1184, P2135, P2228, P2229 are not set.
2. The engine run time is more than 10 seconds.
3. The Vehicle Speed parameter is less than 100 km/h (60 mph).
4. This DTC runs continuously within the enabling conditions in a 250 ms loop.

1. The PCM detects that 80 out of 100 consecutive BARO sensor samples vary more than 10 kPa between each sample.
2. The above condition is met for 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 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 P2227

The barometric pressure (BARO) sensor is a transducer that varies resistance according to changes in altitude and atmospheric conditions. This gives the powertrain control module (PCM) an indication of the current barometric pressure. The PCM 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 PCM supplies 5 volts to the BARO sensor on a 5-volt reference circuit, and provides a ground on the low reference circuit. The BARO sensor provides a voltage signal to the PCM on a signal circuit relative to the pressure changes. The PCM monitors the BARO sensor signal for voltage outside of the normal range. If the PCM detects a BARO sensor signal voltage that is excessively low, DTC P2228 sets.

This diagnostic procedure supports the following DTC

DTC P2228 Barometric Pressure (BARO) Sensor Circuit Low Voltage

The ignition is ON.

OR

The engine is cranking or running.

The PCM detects that the BARO is less than 50 kPa for more than 8 seconds.

OR

The PCM detects that the BARO signal voltage is less than 0.51 volt for more than 8 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 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.

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

1. 2: The BARO sensor 5-volt reference circuit is shared with other sensors. If DTC P0641 is set, this indicates a shorted 5-volt reference circuit or a shorted component and should be diagnosed first.

DTC P2228

The barometric pressure (BARO) sensor is a transducer that varies resistance according to changes in altitude and atmospheric conditions. This gives the powertrain control module (PCM) an indication of the current barometric pressure. The PCM 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 PCM 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 PCM on a signal circuit relative to the pressure changes. The PCM monitors the BARO sensor signal for voltage outside of the normal range. If the PCM detects a BARO sensor signal voltage that is excessively high, DTC P2229 sets.

This diagnostic procedure supports the following DTC

DTC P2229 Barometric Pressure (BARO) Sensor Circuit High Voltage

The ignition is ON.

OR

The engine is cranking or running.

The PCM detects that the BARO signal voltage is more than 4.5 volts for more than 8 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 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.

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

1. 2: The BARO sensor 5-volt reference circuit is shared with other sensors. If DTC P0641 is set, this indicates a shorted 5-volt reference circuit or a shorted component and should be diagnosed first.

DTC P2229

See also:
• Diagnostic System Check - Vehicle
• Service Programming System (SPS)
• Circuit Testing
• Accelerator Controls Pedal Replacement
• Control Module References
• Diagnostic Trouble Code (DTC) List - Vehicle
• Engine Controls Connector End Views
• Powertrain Control Module (PCM) Connector End Views
• Intermittent Conditions
• Powertrain Relay Diagnosis
• Wiring Repairs
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Testing for Electrical Intermittents
• Testing for Continuity
• Using Connector Test Adapters
• Measuring Voltage Drop