Diagnostic Instructions

DTC Descriptor

DTC P2122 00: Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage

DTC P2123 00: Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage

DTC P2127 00: Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage

DTC P2128 00: Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage

DTC P2138 00: Accelerator Pedal Position (APP) Sensors 1-2 Not Plausible

DTC P2138 38: Accelerator Pedal Position (APP) Sensors 1-2 Not Plausible

Diagnostic Fault Information

Circuit	Short to Ground	High Resistance	Open	Short to Voltage	Signal Performance
Accelerator Pedal Position (APP) Sensor 1 5-Volt Reference Circuit	P0641 00	P2138 00, P2138 38	P2122 00	P0641 00	--
Accelerator Pedal Position (APP) Sensor 2 5-Volt Reference Circuit	P0651 00	P2138 00, P2138 38	P2127 00	P0651 00, P0190 00	--
Accelerator Pedal Position (APP) Sensor 1 Signal	P2120 00	P2138 00, P2138 38	P2122 00	P0641 00, P2120 00	P2138 00, P2138 38
Accelerator Pedal Position (APP) Sensor 2 Signal	P2125 00	P2138 00, P2138 38	P2127 00	P2128 00	P2138 00, P2138 38
Accelerator Pedal Position (APP) Sensor 1 Low Reference	--	P2138 00, P2138 38	P2122 00	P2123 00	--
Accelerator Pedal Position (APP) Sensor 1 Low Reference	--	P2138 00, P2138 38	P2127 00	P2128 00	--

Typical Scan Tool Data

APP Sensor

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: The engine is operating at idle. Parameter Normal Range: APP Sensor 1 0.9-1.2 V Parameter Normal Range: APP Sensor 2 varies 0.45-0.62 V
5-Volt Reference 1	0 V	0 V	APP 1 2.08 V
5-Volt Reference 2	0 V	0 V	APP 2 0.86 V
APP Sensor 1 Signal	0 V	0 V	5 V
APP Sensor 2 Signal	0 V	0 V	5 V
APP Sensor 1 Low Reference	--	5 V	--
APP Sensor 2 Low Reference	--	5 V	--

Circuit/System Description

The accelerator pedal assembly contains two accelerator pedal position (APP) sensors. The APP sensors are mounted in the pedal assembly and are not serviceable. The APP sensors provide a signal voltage that changes relative to the position of the accelerator pedal. The engine control module (ECM) supplies a separate 5-volt reference and low reference circuit for each of the APP sensors.

The APP sensor 1 signal voltage increases as the pedal is depressed, from approximately 1 V at rest to above 4 V when fully depressed. The APP sensor 2 signal voltage increases as the pedal is depressed, from approximately 0.5 V at rest to more than 2 V with the accelerator pedal fully depressed.

Conditions for Running the DTC

Conditions for Setting the DTC

P2122 00

The APP sensor 1 voltage is less than 0.59 V for more than 4 s.

P2123 00

The APP sensor 1 voltage is more than 4.62 V for more than 4 s.

P2127 00

The APP sensor 2 voltage is less than 0.28 V for more than 4 s.

P2128 00

The APP sensor 2 voltage is more than 2.32 V for more than 4 s.

P2138 00 and P2138 38

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

Action Taken When the DTC Sets

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

Conditions for Clearing the DTC

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

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References

Circuit/System Verification

1. Ignition ON, observe the scan tool APP Sensor parameters. Both readings should be between 0.4-1.5 V.
2. Rapidly depress the accelerator pedal from the rest position to the wide open throttle position and release pedal. Repeat the procedure several times. DTCs P2122, P2123, P2127, P2128 or P2138 should not set.
3. Slowly depress the accelerator pedal to wide open throttle position and then slowly return the pedal to closed throttle. Repeat the procedure several times. DTCs P2122, P2123, P2127, P2128 or P2138 should not set.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B107 Accelerator Pedal Position (APP) Sensor.
2. Test for less than 5 Ω of resistance between the appropriate low reference circuit and ground.

•	APP Sensor 1 low reference circuit terminal 4

•	APP Sensor 2 low reference circuit terminal 5

⇒	If greater than the specified range, test the low reference circuit for a short to voltage, or an open/high resistance. If the circuits test normal, replace the K20 Engine Control Module (ECM).

Note: The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.

3. Ignition ON, test for 4.8-5.2 V between the appropriate 5-volt reference circuit and ground.

•	APP Sensor 1 5-volt reference circuit terminal 2

•	APP Sensor 2 5-volt reference circuit terminal 1

⇒	If less the specified range, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuits test normal, replace the K20 Engine Control Module (ECM).

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuits test normal, replace the K20 Engine Control Module (ECM).

4. Verify the appropriate scan tool APP sensor parameter is less than 0.3 V.

•	APP Sensor 1 signal circuit terminal 3

•	APP Sensor 2 signal circuit terminal 6

⇒	If greater than the specified range, test the appropriate signal circuit for a short to voltage. If the circuits test normal, replace the K20 Engine Control Module (ECM).

5. Install a 3 A fused jumper wire between the appropriate signal circuit and the 5-volt reference circuit. Verify the scan tool APP sensor parameter is greater than 4.8 V.

⇒	If less than the specified range, test the appropriate signal circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the K20 Engine Control Module (ECM).

⇒	If both scan tool APP sensor parameters display greater than the specified range, test the signal circuits for being shorted together condition. If the circuits test normal, replace the K20 Engine Control Module (ECM).

6. If all circuits test normal, replace the B107 Accelerator Pedal Position (APP) Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.