Diagnostic Instructions

DTC Descriptors

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

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

DTC P2125: Accelerator Pedal Position (APP) Sensor 2 Circuit

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

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

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

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	P06A3, P2122	P2138	P2122	P06A3, P2135	P2138
Accelerator Pedal Position (APP) Sensor 1 Signal	P2122	P2138	P2122	P06A3, P2123	P2138
Accelerator Pedal Position (APP) Sensor 1 Low Reference	--	P2138	P2123	--	P2138
Accelerator Pedal Position (APP) Sensor 2 5-Volt Reference Circuit	P0107, P0697	P2138	P2127	P0106, P0108, P0697	P2138
Accelerator Pedal Position (APP) Sensor 1 Signal	P2122	P2138	P2122	P06A3, P2123	P2138
Accelerator Pedal Position (APP) Sensor 2 Low Reference	--	P2138	P2128	--	P2138

Typical Scan Tool Data

APP Sensor 1 and 2

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: The engine is operating at idle. Parameter Normal Range: APP Sensor 1 0.88-1.08 V Parameter Normal Range: APP Sensor 2 0.39-0.59 V
APP Sensor 1 5-Volt Reference	0.00 V	0.00 V	2.75 V
APP Sensor 1 Signal	0.00 V	0.00 V	4.98 V
APP Sensor 1 Low Reference	--	4.94 V	--
APP Sensor 2 5-Volt Reference	0.00 V	0.00 V	1.35 V
APP Sensor 2 Signal	0.00 V	0.00 V	4.98 V
APP Sensor 2 Low Reference	--	4.92 V	--

Circuit/System Description

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-volt 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 percent at rest to above 95 percent when fully depressed.

Conditions for Running the DTC

P2122, P2123, P2127, or P2128

P2138

Conditions for Setting the DTC

P2122

The ECM detects that the APP sensor 1 voltage is less than 0.46 volt for less than 1 second.

P2123

The ECM detects that the APP sensor 1 voltage is greater than 4.7 volts for less than 1 second.

P2127

The ECM detects that the APP sensor 2 voltage is less than 0.32 volt for less than 1 second.

P2128

The ECM detects that the APP sensor 2 voltage is greater than 2.6 volts for less than 1 second.

P2138

The ECM detects that APP sensor 1 and APP sensor 2 disagree greater than 10 percent for less than 1 second.

OR

The ECM detects that both APP sensor 1 and APP sensor 2 are 5 percent greater than the learned minimum position for less than 1 second.

Action Taken When the DTC Sets

Conditions for Clearing the DTC

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

Diagnostic Aids

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

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

Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify DTCs P0697 or P06A3 are not set.

⇒	If a DTC is set, refer to DTC P0641, P0651, P0697, or P06A3.

2. Ignition ON, observe the scan tool APP Sensor 1 and 2 Indicated parameters. Both parameters should be 0 percent.
3. Observe the scan tool APP sensor 1 and 2 Agree/Disagree parameter while performing the following tests:

•	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.

•	The APP sensor 1 and 2 Agree/Disagree parameter should display Agree.

4. Observe the DTC information with a scan tool. DTCs P2122, P2123, P2127, P2128, or P2138 should not set.
5. 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 accelerator pedal assembly.
2. Ignition OFF for 1 minute, test for less than 5 Ω between the low reference circuit terminals listed below and ground.

•	Low reference circuit terminal 2

•	Low reference circuit terminal 4

⇒	If greater than the specified range, test the appropriate low reference circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, test for 4.8-5.2 V between both 5-volt reference circuit terminals listed below and ground.

•	5 volt reference circuit terminal 5

•	5 volt reference circuit terminal 6

⇒	If less than the specified range, test the appropriate 5-volt reference circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Verify the appropriate APP sensor voltage parameter is at 0 V.

⇒	If greater than the specified range, test the appropriate signal circuit terminal listed below for a short to voltage. If the circuit tests normal, replace the ECM.

•	APP sensor 1 signal circuit terminal 3

•	APP sensor 2 signal circuit terminal 1

5. Install a 3 A fused jumper wire between the appropriate signal circuit listed below and the 5-volt reference circuit terminal 6. Verify the appropriate APP sensor voltage parameter is greater than 4.8 V.

•	APP sensor 1 signal circuit terminal 3

•	APP sensor 2 signal circuit terminal 1

⇒	If less than the specified range, test the appropriate signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

6. If all circuits test normal, replace the accelerator pedal assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.