Allison - Automatic Transmission

DTC P0562, P0563, or P2534

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptor
DTC P0562
- System Voltage Low

DTC P0563
- System Voltage High

DTC P2534
- Ignition 1 Switch Circuit Low Voltage

Circuit/System Description

The transmission control module (TCM) requires a switched ignition voltage input to operate. The TCM continuously monitors the ignition voltage.

Conditions for Running the DTC

P0562 or P0563
* Engine Run time is greater than 10 seconds.
* Engine speed is 450 RPM or greater.

P2534
* Battery voltage is between 9-18 V.
* Engine speed is greater than 200 RPM for 5 seconds.

Conditions for Setting the DTC

P0562

The TCM detects ignition voltage greater than 5 V and less than a threshold voltage based on transmission fluid temperature for greater than 25 seconds and DTC P2534 is not set. Threshold is 5 V for temperatures below -60°C (-76°F), 8 V at 0°C (32°F), and 9 V for temperatures above 20°C (68°F).

P0563

The TCM detects ignition voltage above 18 V, 60 percent of the time, over a 10 second interval.

P2534

The TCM detects ignition voltage below 5 V for 30 seconds.

Action Taken When the DTC Sets

P0562 or P0563

DTCs P0562 and P0563 are Type C DTCs.

P2534

DTC P2534 is a Type A DTC.

Conditions for Clearing the DTC

P0562 and P0563

DTCs P0562 and P0563 are Type C DTCs.

P2534

DTC P2534 is a Type A DTC.

Diagnostic Aids

* A defective vehicle battery may allow DTC P0562 to set.
* A defective vehicle charging system may allow DTCs P0562, P0563 or P2534 to set.
* You may have to drive the vehicle in order to experience a condition.
* Although this DTC could indicate an internal voltage condition within the TCM, in most cases, the TCM is not at fault. Investigate thoroughly prior to replacing the TCM.

Reference Information
Schematic Reference

Automatic Transmission Controls Schematics (Diagrams)
Connector End View Reference

* Component Connector End Views (Connector Views)
* Inline Harness Connector End Views (Diagrams)

Description and Operation

* Transmission General Description (Transmission General Description)
* Transmission Component and System Description (Transmission Component and System Description)
* Electronic Component Description (Electronic Component Description)

Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Engine running, accessories OFF, measure and record the battery voltage at the battery terminals. The reading should be between 12.6 and 15 V.

• If not the expected value, refer to Charging System Test (Component Tests and General Diagnostics).

2. Observe the scan tool TCM ignition voltage parameter. The reading should be between 12.6 and 15 V.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

Note: You must perform the Circuit/System Testing first.

1. Ignition OFF, disconnect the harness connector at the TCM.
2. Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes, test for less than 10 ohms between the ground circuit terminal 9 and ground and between terminal 69 and battery ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 63 and ground.

• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If circuit tests normal, replace the TCM.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

Control Module References (Programming and Relearning) for TCM replacement, setup, and programming.

Repair Verification

If another DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle) and perform the appropriate diagnostic procedure.