P2138 Accelerator Pedal Position Sensor 1/2 Correlation

P2138 code - This diagnostic runs continuously when the following conditions are met: With the ignition on, battery voltage greater than 10.4 volts, no accelerator pedal position (APP) sensor 1 DTCs present, no accelerator pedal position (APP) sensor 2 DTCs present. Set condition the Powertrain Control Module (PCM) detects that the correlation between APP sensor 1 and APP sensor 2 is not plausible. Default action the MIL light illuminate, the ETC light flash, the Throttle input and vehicle speed are limited.

P2138 code

Possible causes P2138 code

- High resistance in a 5-Volt supply circuit
- High resistance in the APP sensor signal 1 circuit
- High resistance in the APP sensor 1 ground circuit
- High resistance in the APP sensor signal 2 circuit
- High resistance in the APP sensor 2 ground circuit
- Accelerator pedal position sensor
- Powertrain Control Module (PCM)

Diagnostic test P2138 code

Step 1. Check for an active DTC
Turn the ignition on, slowly press and release the accelerator pedal several times. With the scan tool read DTCs and record on the repair order.

Is the DTC active or pending?

Yes, go to step 2.
No, perform the PCM intermittent condition.

Step 2. Check for high resistance in the 5-volt supply circuit
Turn the ignition off, disconnect the APP sensor harness conector. Disconnect the PCM harness connector. Do not probe the PCM harness connectos. Probing the PCM harness connectors will damage the PCM terminals resulting ti pin connection. Measure the resistance of the 5-volt supply circuit between the APP sensor harness connector and PCM harness connector.

Is the resistance below 3.0 ohms?

Yes, go to step 3.
No, repair the 5-volt supply circuit for an open or high resistance.

Step 3. Check for high resistance in the APP sensor signal 1 circuit
Measure the resistance of the APP sensor signal 1 circuit between the APP sensor harness connector and the PCM harness connector.

Is the resistance below 3.0 Ohms?

Yes, go to step 4.
No, repair the APP sensor signal 1 circuit for an open or high resistance.

Step 4. Check for high resistance in the APP sensor ground 1 circuit
Measure the resistance of the APP sensor 1 ground circuit between the APP sensor harness connector and the PCM harness connector.

Is the resistance below 3.0 Ohms?

Yes, go to step 5.
No, repair the APP sensor 1 ground circuit for an open or high resistance.

Step 5. Check for high resistance in the 5-volt supply circuit
Measure the resistance of the 5-volt supply circuit between the APP sensor harness connector and the PCM harness connector.

Is the resistance below 3.0 Ohms?

Yes, go to step 6.
No, repair the 5-volt supply circuit for an open or high resistance.

Step 6. Check for high resistance in the APP sensor signal 2 circuit
Measure the resistance of the APP sensor signal 2 circuit between the APP sensor harness connector and the PCM harness connector.

Is the resistance below 3.0 Ohms?

Yes, go to step 7.
No, repair the APP sensor signal 2 circuit for an open or high resistance

Step 7. Check for high resistance in the APP sensor 2 ground circuit
Measure the resistance of the APP sensor 2 ground circuit between the APP sensor harness connector and the PCM harness connector.

Is the resistance below 3.0 Ohms?

Yes, go to step 8.
No, repair the APP sensor 2 ground circuit for an open or high resistance.

Step 8. Accelerator pedal position sensor
Turn the ignition off, reconnect the APP sensor harness connector. Reconnect the PCM harness connector, turn the ignition on. Set up a lab scope to view two graphs simultaneously. Using the one chennel on the lab scope, probe the APP signal 1 circuit at the PCM harness connector. Using the other channel on the lab scope, probe the APP sensor 2 circuit at the PCM harness connector. Slowly press and release the accelerator pedal while monitoring the lab scope screen.

Does the scope pattern show any missing or erratic signals?

Yes, replace the accelerator pedal position sensor.
No, go to step 9.

Step 9. Check related PCM and component connections

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