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Home >> Chevrolet >> 2012 >> Volt L4-1.4L Elect >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> P Code Charts >> P0121

P0121




DTC P0121-P0123, P0222, P0223, or P2135

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors
DTC P0121
- Throttle Position Sensor 1 Performance

DTC P0122
- Throttle Position Sensor 1 Circuit Low Voltage

DTC P0123
- Throttle Position Sensor 1 Circuit High Voltage

DTC P0222
- Throttle Position Sensor 2 Circuit Low Voltage

DTC P0223
- Throttle Position Sensor 2 Circuit High Voltage

DTC P2135
- Throttle Position Sensors 1-2 Not Plausible

Diagnostic Fault Information






Typical Scan Tool Data










Circuit/System Description

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

The TP sensors have opposite functionality. TP sensor 1 signal voltage decreases and TP sensor 2 signal voltage increases.

Conditions for Running the DTC

P0121
* DTCs P0102, P0103, P0107, P0108, P0111, P0112, P0113, P0114, P0116, P0117, P0118, P0119, P0128, P0335, or P0336 is not set.
* The engine speed is between 500-8,000 RPM.
* The engine coolant temperature (ECT) is between -7 to +125°C (19-257°F).
* The intake air temperature (IAT) is between -20 to +125°C (-4 to +257°F).
* The DTC runs continuously when the above conditions are met.

P0122, P0123, P0222, P0223
* DTC P06A3 is not set.
* The run/crank voltage is greater than 6.4 V.
* The ignition is ON.
* The DTCs runs continuously when the above condition are met.

P2135
* DTCs P0122, P0123, P0222, P0223, and P06A3 is not set.
* The run/crank voltage is greater than 6.4 V.
* The ignition is ON.
* The DTC runs continuously when the above conditions are met.

Conditions for Setting the DTC

P0121

The ECM detects that the TP sensor 1 voltage is stuck in range for greater than 1 s.

P0122

The ECM detects that the TP sensor 1 voltage is less than 0.32 V for greater than 1 s.

P0123

The ECM detects that the TP sensor 1 voltage is greater than 4.7 V for greater than 1 s.

P0222

The ECM detects that the TP sensor 2 voltage is less than 0.25 V for greater than 1 s.

P0223

The ECM detects that the TP sensor 2 voltage is greater than 4.6 V for greater than 1 s.

P2135

The ECM detects that TP sensor 1 and TP sensor 2 disagree greater than 7-10 percent for greater than 1 s.

Action Taken When the DTC Sets

P0121
* DTC P0121 is a Type B DTC.
* A message center displays Propulsion Power is Reduced.
* Under certain conditions, the ECM commands the engine OFF.

P0122, P0123, P0222, P0223, or P2135
* DTC P0122, P0123, P0222, P0223, and P2135 are Type A DTCs.
* A message center displays Propulsion Power is Reduced.
* Under certain conditions, the ECM commands the engine OFF.

Conditions for Clearing the DTC

* DTC P0121 is a Type B DTC.
* DTC P0122, P0123, P0222, P0223, and P2135 are Type A DTCs.

Diagnostic Aids

A high resistance condition on the throttle position and throttle actuator control circuits could cause a DTC to set.

Reference Information
Schematic Reference

Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference

Component Connector End Views Hybrid/EV Battery Pack X1
Description and Operation

Hybrid Modes of Operation Description Hybrid Modes of Operation Description

Throttle Actuator Control (TAC) System Description Throttle Actuator Control (TAC) System Description
Electrical Information Reference

* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference

Control Module References Programming and Relearning for scan tool information

Circuit/System Verification

1. Vehicle in Service Mode.
2. Verify DTC P06A3 is not set.

• If any of the DTCs are set
Refer to DTC P0641, P0651, P0697, or P06A3 (ECM) Powertrain Management (ECM) for further diagnosis.

• If none of the DTCs are set

3. Verify the scan tool Throttle Body Idle Air Flow Compensation parameter is less than 90 %.

• 90 % or greater
Refer to Throttle Body Inspection and Cleaning Procedures

• If less than 90 %

4. Verify the scan tool Throttle Position Sensor 1 and Throttle Position Sensor 2 voltage parameters are between 1.0-4.0 V.

• If not between 1.0-4.0 V
Refer to Circuit/System Testing

• If between 1.0-4.0 V

5. Verify the Throttle Position Sensors 1 and 2 Agree/Disagree parameter displays Agree while performing the Throttle Sweep Test with a scan tool.

• If Disagree
Test or replace the Q38 throttle body assembly.

• If Agree

6. Verify DTC P0121, P0122, P0123, P0222, P0223, and P2135 is not set.

• If any of the DTCs are set
Refer to Circuit/System Testing

• If none of the DTCs are set

7. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
8. Verify a DTC does not set.

• If any DTC sets
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

• If no DTCs set

9. All OK

Circuit/System Testing

Note: Disconnecting the throttle body harness connector causes additional DTCs to set.

1. Vehicle OFF, and all vehicle systems OFF, disconnect the harness connector at Q38 throttle body assembly. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 5 ohm between the low reference circuit terminal C and ground.

• If 5 ohm or greater

1. Vehicle OFF, disconnect the harness connector at the K20 engine control module.
2. Test for less than 2 ohm in the low reference circuit end to end.

• If 2 ohm or greater, repair the open/high resistance in the circuit.
• If less than 2 ohm, replace the K20 engine control module.

• If less than 5 ohm

3. Vehicle in Service Mode.
4. Test for 4.8-5.2 V between the 5 V reference circuit terminal E and ground.

• If less than 4.8 V

1. Vehicle OFF, disconnect the harness connector at the K20 engine control module.
2. Test for infinite resistance between the 5 V reference circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohm in the 5 V reference circuit end to end.

• If 2 ohm or greater, repair the open/high resistance in the circuit.
• If less than 2 ohm, replace the K20 engine control module.

• If greater than 5.2 V

1. Vehicle OFF, disconnect the harness connector at the K20 engine control module, vehicle in Service Mode.
2. Test for less than 1 V between the 5 V reference circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 engine control module.

• If between 4.8-5.2 V

5. Vehicle in Service Mode.
6. Test for less than 1 V between the throttle position sensor 1 signal circuit terminal D and ground.

• If 1 V or greater

1. Vehicle OFF, disconnect the harness connector at the K20 engine control module, vehicle in Service Mode.
2. Test for less than 1 V between the signal circuit terminal D and ground.

• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 engine control module.

• If less than 1 V

7. Install a 3 A fused jumper wire between throttle position sensor 1 signal circuit terminal D and the 5 V reference circuit terminal E.
8. Verify the scan tool Throttle Position Sensor 1 voltage parameter is greater than 4.8 V.

• If less than 4.8 V

1. Vehicle OFF, disconnect the harness connector at the K20 engine control module.
2. Test for infinite resistance between the signal circuit terminal and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohm in the signal circuit end to end.

• If 2 ohm or greater, repair the open/high resistance in the circuit.
• If less than 2 ohm, replace the K20 engine control module.

• If greater than 4.8 V

9. Test for 4.8-5.2 V between the throttle position sensor 2 signal circuit terminal F and ground.

• If less than 4.8 V

1. Vehicle OFF, disconnect the harness connector at the K20 engine control module.
2. Test for infinite resistance between the signal circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohm in the 5 V reference circuit end to end.

• If 2 ohm or greater, repair the open/high resistance in the circuit.
• If less than 2 ohm, replace the K20 engine control module.

• If greater than 5.2 V

1. Vehicle OFF, disconnect the harness connector at the K20 engine control module, vehicle in Service Mode.
2. Test for less than 1 V between the signal circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 engine control module.

• If between 4.8-5.2 V

10. Test or replace the Q38 throttle body assembly.

Repair Instructions

* Throttle Body Assembly Replacement Removal and Replacement
* Control Module References Programming and Relearning for ECM replacement, programming, and setup

Repair Verification

1. Install any components that have been removed or replaced during diagnosis.
2. Perform any adjustments, programming or setup procedures that are required when a component is removed or replaced.
3. Clear the DTCs with a scan tool.
4. Vehicle OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down.
5. Vehicle in Service Mode.
6. Verify the Throttle Position Sensors 1 and 2 Agree/Disagree parameter displays Agree while performing the Throttle Sweep Test with a scan tool.

• If Disagree
Test or replace the Q38 throttle body assembly.

• If Agree

7. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset.

• If any DTC sets
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

• If no DTC sets

8. All OK

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