Volt

DTC P2122, P2123, P2127, P2128, or P2138

The accelerator pedal assembly contains 2 accelerator pedal position (APP) sensors. The APP sensors are mounted to the accelerator pedal assembly and are not serviceable. The APP sensors provide a signal voltage that changes relative to pedal position. The engine control module (ECM) supplies each APP sensor with a 5 V reference circuit, a low reference circuit, and a signal circuit. Both the APP sensors 1 and 2 signal percentages increase as the pedal is depressed, from approximately 0% at rest to above 95% when fully depressed.

The ECM provides the accelerator pedal position or driver torque request to the hybrid powertrain control module. The hybrid powertrain control module determines how the torque output will be distributed between the two electric motors and the engine.

P2122, P2123, P2127, P2128

P2138

P2122

The ECM detects that the APP sensor 1 voltage is less than 0.46 V for greater than 1 s.

P2123

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

P2127

The ECM detects that the APP sensor 2 voltage is less than 0.32 V for greater than 1 s.

P2128

The ECM detects that APP sensor 2 voltage is greater than 2.6 V for greater than 0.5 s.

P2138

The voltage difference between APP sensor 1 and APP sensor 2 exceeds a predetermined value for greater than 1 s.

DTCs P2122, P2123, P2127, and P2128, and P2138 are Type A DTCs.

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 P0697 or P06A3 is not set.

⇒	If any of the DTCs are set

Refer to for DTC P0641, P0651, P0697, or P06A3 : ECM further diagnosis.

⇓	If none of the DTCs are set

3. Verify the APP Sensor 1 Circuit Status and APP Sensor 2 Circuit Status displays OK.

⇒	If Malfunction is displayed

Refer to Circuit/System Testing

⇓	If OK is displayed

4. Verify the scan tool APP Sensor 1 and 2 Agree/Disagree parameter displays Agree while performing the tests listed below:

•	Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times.

•	Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times.

⇒	If Disagree

Refer to Circuit/System Testing

⇓

If Agree

5. Verify that DTC P2122, P2123, P2127, P2128, or P2138 is not set.

⇒	If any of the DTCs are set

Refer to Circuit/System Testing

⇓	If none of the DTCs set

6. 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.
7. Verify DTC P2122, P2123, P2127, P2128, or P2138 is not set.

⇒	If any DTC sets

Refer to Circuit/System Testing

⇓	If no DTCs set

8. All OK

1. Vehicle OFF and all vehicle systems OFF, disconnect the harness connector at the B107 accelerator pedal assembly. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 5 Ω between each low reference circuit terminal listed below and ground.

•	Low reference circuit terminal 4 or A

•	Low reference circuit terminal 5 or D

⇒	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 each 5 V reference circuit terminal listed below and ground.

•	5 V reference circuit terminal 1 or C

•	5 V reference circuit terminal 2 or F

⇒	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. Verify each APP sensor voltage parameter is less than 0.2 V.

⇒	If 0.2 V or greater

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

5.2.	Test for less than 1 V between the signal circuit terminal listed below and ground.

•	APP sensor 1 signal circuit terminal 3 or E

•	APP sensor 2 signal circuit terminal 6 or B

⇒	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 0.2 V

6. Install a 3 A fused jumper wire between each signal circuit terminal listed below and the 5 V reference circuit terminal 1.

•	APP sensor 1 signal circuit terminal 3 or E

•	APP sensor 2 signal circuit terminal 6 or B

7. Verify the scan tool APP sensor voltage parameter is greater than 4.8 V.

⇒	If 4.8 V or less

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

7.2.	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

7.3.	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

8. Test or replace the B107 accelerator pedal assembly.

Perform the Diagnostic Repair Verification after completing the repair.