For 1990-2009 cars

### 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 P2536: Ignition Accessory Switch Circuit

### Circuit/System Description

The transmission control module (TCM) continuously monitors the ignition accessory voltage circuit. A low ignition accessory voltage reading at the TCM will cause DTC P2536 to set.

### Conditions for Running the DTC

• | No Engine Speed Circuit Malfunction, DTC P0727.

• | No Lost Communications with the ECM, DTC U0100.

• | NO CAN Bus Reset Counter Overrun, DTC U2104.

• | Engine speed is 400 RPM or greater.

• | Not in Emergency Mode.

### Conditions for Setting the DTC

The TCM detects that ignition accessory voltage is less than 8.68 volts for 20 seconds.

### Action Taken When the DTC Sets

DTC P2536 is a Type A DTC.

### Conditions for Clearing the DTC

DTC P2536 is a Type A DTC.

### Diagnostic Aids

A charging system malfunction may cause variances in system voltage and set voltage related DTCs. Refer to Charging System Test .

### Reference Information

#### Schematic Reference

Automatic Transmission Controls Schematics

#### Connector End View Reference

• | Automatic Transmission Inline Harness Connector End View

• | Automatic Transmission Internal Connector End Views

• | Automatic Transmission Related Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

• | Diagnostic Trouble Code (DTC) Type Definitions

• | Diagnostic Trouble Code (DTC) List/Type

#### Scan Tool Reference

• | Scan Tool Output Controls

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Verification

Engine running, verify the transmission control module (TCM) scan tool ignition voltage parameter is greater than 8.68 volts.

⇒ | If not greater than the specified range, refer to Charging System Test before performing Circuit/System Testing.

### Circuit/System Testing

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the C1 harness connector at the TCM.
2. Test for less than 1.0ohms of resistance between ground circuit terminal 9 and ground.

⇒ | If greater than the specified value, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 12 and ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, replace the TCM.

4. If all circuits test normal, replace the TCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.