M99 - Automatic Transmission

DTC P2534

Diagnostic Instructions

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



DTC Descriptor
DTC P2534
- Ignition 1 Switch Circuit Low Voltage




Diagnostic Fault Information






Typical Scan Tool Data






Circuit/System Description

The transmission control module (TCM) samples the system voltage on the Ignition 1 voltage circuit every 0.1 seconds. Lower than normal voltage may be inadequate to operate the transmission control solenoids properly. Improper solenoid operation may cause erratic transmission operation, which may result in internal damage.


Conditions for Running the DTC

* The engine speed is greater than 500 RPM.
* Ignition voltage is between 8-18 volts.



Conditions for Setting the DTC

The TCM detects 2 volts or less on the ignition 1 voltage circuit at the TCM for 10 seconds or more.


Action Taken When the DTC Sets

* DTC P2534 is a Type A DTC.
* The TCM turns OFF all high side drivers.
* The TCM turns OFF all solenoids.
* The TCM commands maximum line pressure.
* The TCM freezes transmission adaptive functions.
* The TCM allows the vehicle to operate in transmission protection mode.



Conditions for Clearing the DTC

DTC P2534 is a Type A DTC.


Diagnostic Aids

If all circuit tests are OK, ensure the transmission pass through connector and harness terminals are clean and not damaged, and the charging system is functioning correctly.
The transmission 24-way inline harness connector must be disconnected prior to disconnecting the transmission 16-way inline harness connector



Reference Information
Schematic Reference

Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views
Electrical Information Reference

* Circuit Testing
* Connector Repairs
* Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs
* High Voltage Disabling
* High Voltage Enabling

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions


Circuit/System Testing

1. Ignition OFF, disconnect the transmission 24-way inline harness connector, then the transmission 16-way in line harness connector at the transmission, verify that a test lamp does not illuminate between the ignition 1 voltage circuit terminal 12 and ground.

• If the test lamp illuminates, test the ignition 1 voltage circuit for a short to voltage.

2. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 12 and ground.

• If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance.
• If the circuit tests normal replace the control solenoid (w/body and TCM) valve assembly.




Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


Control solenoid (w/body and TCM) valve assembly replacement. Refer to Control Module References for replacement, setup, and programming.