P2122, P2127 Accelerator Pedal Position Sensor 1 and 2 Circuit Low

P2122, P2127 code - The Electronic Throttle Control (ETC) system uses two Accelerator Pedal Position (APP) Sensors to monitor the accelerator pedal position. The APP sensors 1 and 2 are integrated into one assembly located at the pedal assembly. Each sensor has a 5 volt reference circuit, a low reference circuit, and signal circuit. The Powertrain Control Module (PCM) reads the two signals individually and then compares the two signals as a redundant check of the pedal position. One of the sensors will fluctuate somewhere between 0 volts and 5.0 volts and the other sensor will fluctuate somewhere between 0 volts and 2.5 volts. The fluctuation of the two sensors should move propertionately. When operating properly, the voltage reading of the sensor operating on the 2.5 volt scale will always be appropximately half of the voltage reading of the sensor on the 5.0 volt scale.

Set condition this DTC the Powertrain Control Module (PCM) detects that the APP sensor 1 input voltage is below the minimum acceptable value. Default actions the MIL light illuminate, the ETC light flash, the Throttle input and vehicle speed are limited.

Possible causes P2122, P2127 code

- 5 volt supply circuit open or shorted to ground
- APP sensor 1 signal circuit shorted to ground
- APP sensor 1 signal circuit shorted to the APP sensor 1 ground circuit
- APP sensor 1 signal circuit shorted to the APP sensor 2 ground circuit
- APP sensor 1 signal circuit open/high resistance
- APP sensor 1 ground circuit open/high resistance
- Accelerator pedal position sensor
- Powertrain Control Module (PCM)

Diagnostic test P2122, P2127 code

Step 1. Check for an active DTC
Diagnose and repair any 5-volt sensor supply voltage DTCs before continuing with this test. Turn the ignition on, with the scan tool read DTCs.

Is the DTC active or pending?

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

Step 2. Check the 5 volt supply circuit voltage
Turn the ignition off, disconnect the accelerator pedal position sensor harness connector. Turn the ignition on, measure the voltage between ground and the 5 volt supply circuit in the accelerator pedal position sensor harness connector.

Is the voltage between 4.9 and 5.2 volts?

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

Step 3. Check the APP sensor 1 signal circuit for a short to ground
Disconnect the PCM harness connector, measure the resistance between ground and the APP sensor 1 signal circuit in the Accelerator Pedal Position sensor harness connector.

Is the resistance above 10k Ohms?

Yes, go to step 4.
No, repair the APP sensor 1 signal circuit for a short to ground.

Step 4. Check for the APP sensor 1 signal circuit shorted to the sensor ground circuits
Measure the resistance beween the APP sensor 1 signal circuit and the:
- Sensor ground circuit in the accelerator pedal position sensor 1 harness connector.
- Sensor ground circuit in the accelerator pedal position sensor 2 harness connector.

Is the resistance above 10k Ohms?

Yes, go to step 5.
No, repair the APP signal 1 circuit for a short to the sensor ground circuit that measured below 10k Ohms.

Step 5. Check the APP sensor 1 signal circuit for an open or high resistance
Do not probe the PCM harness connecors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection.
Measure the resistance of the APP sensor 1 signal circuit between the accelerator pedal position sensor harness connector and the PCM harness connector.

Is the resistance below 3.0 Ohms?

Yes, go to step 6.
No, repair the APP sensor 1 signal circuit for an open or high resistance.

Step 6. Check the APP sensor ground 1 circuit for an open or high resistance
Measure the resistance of the APP sensor ground 1 circuit between the Accelerator pedal position 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 ground 1 circuit for an open circuit or high resistance.

Step 7. Check the Accelerator pedal position sensor
Reconnect the PCM harness connector, connect a jumper between the 5-volt supply circuit and the APP sensor 1 signal circuit in the accelerator pedal position sensor harness connector. Turn the ignition on, with the scan tool read the accelerator pedal position sensor signal voltage.

Is the voltage above 4.9 volts with the jumper in place?

Yes, replace the accelerator pedal position sensor.
No, go to step 8.

Step 8. Check related PCM and component connections

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