Volt

DTC P0121-P0123, P0222, P0223, or P2135

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.

P0121

P0122, P0123, P0222, P0223

P2135

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.

P0121

P0122, P0123, P0222, P0223, or P2135

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

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Hybrid Modes of Operation Description

Throttle Actuator Control (TAC) System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

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 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

⇓	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 for further diagnosis.

⇓	If no DTCs set

9. All OK

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 Ω between the low reference circuit terminal C and ground.

⇒	If 5 Ω or greater

2.1.	Vehicle OFF, disconnect the harness connector at the K20 engine control module.

2.2.	Test for less than 2 Ω in the low reference circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K20 engine control module.

⇓	If less than 5 Ω

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

4.1.	Vehicle OFF, disconnect the harness connector at the K20 engine control module.

4.2.	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

4.3.	Test for less than 2 Ω in the 5 V reference circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K20 engine control module.

⇒	If greater than 5.2 V

4.1.	Vehicle OFF, disconnect the harness connector at the K20 engine control module, vehicle in Service Mode.

4.2.	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

6.1.	Vehicle OFF, disconnect the harness connector at the K20 engine control module, vehicle in Service Mode.

6.2.	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

8.1.	Vehicle OFF, disconnect the harness connector at the K20 engine control module.

8.2.	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

8.3.	Test for less than 2 Ω in the signal circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, 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

9.1.	Vehicle OFF, disconnect the harness connector at the K20 engine control module.

9.2.	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

9.3.	Test for less than 2 Ω in the 5 V reference circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K20 engine control module.

⇒	If greater than 5.2 V

9.1.	Vehicle OFF, disconnect the harness connector at the K20 engine control module, vehicle in Service Mode.

9.2.	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.

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 for further diagnosis.

⇓	If no DTC sets

8. All OK