Allison 3000 & 4000 Gen 5 P0122 Pedal Position Sensor Circuit Low Repair

This instruction show you guide on how to solve fault code P0122 pedal position sensor circuit low voltage for Allison 3000 & 4000 Gen 5.

Allison 3000 & 4000 Gen 5


Use default throttle values. Freezes shift adapts.


For more Diesel machine repair,please refer to:

2023 Diesel DTC Solutions V2.9.98+ Diesel Explorer 2.0+Instruction



The TCM may be calibrated to receive an analog Throttle Position Sensor (TPS) pedal position signal from a TPS. Throttle position information comes from a resistive sensor. The resistive throttle sensor is attached to throttle linkage. This device produces a voltage proportional to throttle position.


NOTE: Refer to Throttle Position Sensor (TPS) Adjustment for the TPS adjustment procedure and signal voltage specifications.


NOTE: The transmission TPS is not the same accelerator pedal sensor that the driver actuates to accelerate the vehicle. The transmission TPS is not used to fuel, accelerate, or decelerate the engine or vehicle. The transmission TPS is only wired to the transmission TCM and is only used for shift scheduling purposes based on the TPS signal amount (shown as TPS voltage in Data Monitor).


The TCM is connected to the TPS by:

1 A 5V reference voltage (W112),

2 TPS signal (W144 ), and

3 Analog ground (W158).

The TCM provides a 5V reference voltage to the TPS. The varying voltage at W144 is interpreted as pedal position and the driver’s demand for engine torque and vehicle speed. The TCM uses this TPS information for transmission shift scheduling and modulation.



When DTC P0122 is active, the following conditions occur:

1 CHECK TRANS light ilumninates.

2 DTC is stored in TCM history.

3 Default value used for % throttle based on engine torque and engine speed.


Use the diagnostic tool to clear the DTC from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without failure.



DTC P0122 indicates the TCM has detected a voltage signal from the TPS in the low error zone, and may be caused by the following:

1 Open or short to ground in W112 or W144 circuits.

NOTE: Shorts or opens in W112 typically will log other sensor failed low DTCS that are using W112 (5V), such as the Oil Level Sensor (OLS), or Retarder Modulation Request (RMR) Sensor. Shorts or opens in W144 (TPS signal) only causes DTC P0122.

2 Analog TPS source set in calibration in non-analog TPS applications.

3 Analog TPS source set by CMC Override Throttle Source using the diagnostic tool in non-analog TPS application.

4 Missing, defective, or unplugged TPS.

5 Defective sensor sharing 5V supply.

6 5V wire open or grounded in transmission internal harness.

7 Broken or defective connector assemblies allowing pushed back pins to short together.

8 Unlocked connectors, missing seal plugs allowing moisture in connectors.

10 TPS not adjusted. Refer to Throttle Position Sensor (TPS) Adjustment.

Review applicable information in Control System and Transmission Specifications to find additional circuit specifications, system and connector diagrams, and troubleshooting tips.


More Allison repair case,please refer to Allison Trouble Repair

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