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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2007 🢒 Vibe - FWD 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P2138

Circuit Description

The DTC P2138 Accelerator Pedal Position (APP) Sensor 1-2 Correlation diagnostic monitors the APP sensor 1 signal circuit. The accelerator pedal assembly contains 2 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 powertrain control module (PCM) 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 0.75 volt at rest to about 4 volts when fully depressed. The APP sensor 2 signal voltage increases as the pedal is depressed, from approximately 1.6 volts at rest to more than 4.8 volts with the accelerator pedal fully depressed.

DTC Descriptor

This diagnostic procedure supports the following DTC:

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

Conditions for Running the DTC
    • The ignition is ON or the engine is running.
    • DTC P2138 runs continuously once the above condition has been met.

Conditions for Setting the DTC

One or more of the following conditions are present:

    • The difference between the APP sensor 1 signal and the APP sensor 2 signal is less than 0.2 volt for at least 2 seconds.
    • The APP sensor 1 input to the PCM is less than 0.2 volt for at least 2 seconds.
    • The APP sensor 2 input to the PCM is less than 0.5 volt for at least 2 seconds.

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL).
    • The PCM stores the conditions that were present when the DTC set as Freeze Frame data.
    • The engine will operate in the reduced power mode and the APP sensor angle will default to idle.

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the MIL on the third consecutive trip in which the diagnostic runs without a fault.
    • The PCM clears a History DTC after 40 consecutive warm-up cycles without a fault.
    • You use the scan tool Clear DTC Information function.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

    2.

  2. If there are any other APP sensor or any TAC system DTCs set, diagnose those DTCs first.

    3.

  3. This step tests the input circuit wiring and the PCM. If the scan tool displays approximately 5 volts, the PCM and input circuit are OK.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Are any throttle actuator control (TAC) system or other accelerator pedal position (APP) sensor DTCs set?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 3

3

  1. Turn the ignition ON, with the engine OFF.
  2. With the throttle closed, select the APP Sensor 1 parameter on the scan tool.

Is the APP Sensor 1 voltage within the specified value?

0.75-0.85 V

Go to Step 5

Go to Step 4

4

  1. Turn the ignition ON, with the engine OFF.
  2. With the throttle closed, select the APP Sensor 2 parameter on the scan tool.

Is the APP Sensor 2 voltage within the specified value?

1.55-1.70 V

Go to Step 8

Go to Step 7

5
  1. Turn the ignition ON, with the engine OFF.
  2. With the throttle closed, select the APP Sensor 2 parameter on the scan tool.

Is the APP Sensor 2 voltage within the specified value?

1.55-1.7 V

Go to Step 6

Go to Step 10

6
  1. Perform the scan tool Clear DTC Information function.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Freeze Frame conditions as specified.

Does DTC 2138 set?

--

Go to Step 3

Go to Intermittent Conditions

7
  1. Test for a short between the APP sensor 1 and APP sensor 2 signal circuits.
  2. Repair as necessary. Refer to Wiring Repairs .

Did you find and repair a condition?

--

Go to Step 15

Go to Step 13

8
  1. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the APP sensor 1 and the sensor signal circuit.
  2. Observe the APP sensor 1 parameter on the scan tool.

Is the APP sensor 1 voltage within the specified range?

4.8-5.2 V

Go to Step 12

Go to Step 9

9

  1. Test for the following conditions:
    2. • An open in the input circuit of the APP sensor 1
    • An open in the low reference circuit of the APP sensor 1
    • An intermittent or a poor electrical connection at the powertrain control module (PCM)--Refer to Testing for Intermittent Conditions and Poor Connections .
  2. Repair as necessary. Refer to Wiring Repairs .

Did you find and correct a condition?

--

Go to Step 15

Go to Step 14

10
  1. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the APP sensor 2 and the sensor signal circuit.
  2. Observe the APP sensor 2 parameter on the scan tool.

Is the APP sensor 2 voltage within the specified range?

4.8-5.2 V

Go to Step 12

Go to Step 11

11
  1. Test for the following conditions:
    2. • An open in the input circuit of the APP sensor 2
    • An open in the low reference circuit of the APP sensor 2
    • An intermittent or a poor electrical connection at the PCM--Refer to Testing for Intermittent Conditions and Poor Connections .
  2. Repair as necessary. Refer to Wiring Repairs .

Did you find and correct a condition?

--

Go to Step 15

Go to Step 14

12
  1. Test for an intermittent or a poor electrical connection at the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
  2. Repair as necessary.

Did you find and correct a condition?

--

Go to Step 15

Go to Step 13

13

Replace the APP sensor. Refer to Accelerator Pedal Position Sensor Replacement .

Did you complete the replacement?

--

Go to Step 15

--

14

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 15

--

15
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 16

Go to Step 2

16

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK