P0875

ALLISON AUTOMATIC TRANSMISSION

DTC P0875

DTC P0875 Step 1 - 8:

DTC P0875 Step 9 - 13:

Circuit Description for Allison Automatic Transmission

Important: DTC P0875 was previously P1713.

The Pressure Switch Manifold (PSM) is a multiple switch assembly made up of three Normally Open (N/O) pressure switches and one Normally Closed (N/C) pressure switch for reverse pressure.

Fluid pressure is supplied to the reverse pressure switch when the manual selector valve is in any position except reverse. When the manual selector valve is moved to Reverse, pressure to the reverse pressure switch is cut off causing the switch to close.

DTC P0875 is a type A DTC.

Conditions for Running the DTC
^ The components are powered and ignition voltage is greater than 9V and less than 18 V.
^ Engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds.
^ The Park/Neutral Position switch is enabled and functional.
^ TFT is greater than 0°C (32°F).
^ DTCs P0706, P0708, P1714, P1715 are not active.

Conditions for Setting the DTC
DTC P0875 sets when Park, Neutral, or a forward range is selected and the reverse pressure switch remains in the mechanically closed/electrically on position for a period of time that is calibration dependent.

Action Taken When the DTC Sets
^ The TCM will illuminate the Malfunction Indicator Lamp (MIL).
^ The transmission will lock in neutral.
^ DTC P0875 will be stored in the TCM history.
^ The TCM freezes shift adapts (DNA).
^ TCM inhibits TCC engagement.

Conditions for Clearing the MIL/DTC
A scan tool can clear the code from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without failure.

Diagnostic Aids
^ Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
- A bent terminal
- A backed-out terminal
- A damaged terminal
- Poor terminal tension
- A chafed wire
- A broken wire inside the insulation
^ When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
^ You may have to drive the vehicle in order to experience a fault.
^ This DTC could indicate a hydraulic leak path exhausting pressure from the reverse pressure switch.
^ An inactive DTC P0875 (previously P1713) set in combination with DTC P0872 (previously P1711) often indicates that an internal PNP switch failure occurred on a previous drive cycle. If this combination returns after clearing DTCs, replacement of the PNP switch may be necessary.
^ The intent of this code is to detect discrepancies between range selected at the PNP and the actual position of the manual selector valve.

Test Description
The numbers refer to the step numbers on the diagnostic table.
5. This step tests the TCM response function.
6. This step tests the transmission wiring harness integrity.
7. This step tests and evaluates the internal wiring harness.
8. This step tests the Pressure Switch Manifold (PSM) for a failed condition.