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 P2534: Ignition 1 Switch Circuit Low Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition 1 voltage | P2534 open fuse | P2534 | -- | P0562, P0563

### Typical Scan Tool Data

#### Ignition 1 Voltage

Circuit | Short to Ground | Open/High Resistance | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Ignition ON Parameter Normal Range: 0-19 volts
Ignition 1 voltage | 0 Volts | 0 Volts | --

### Circuit/System Description

The transmission control module (TCM) continuously monitors the system voltage on the Ignition 1 voltage circuit every 0.025 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 for 5 seconds.

• | Ignition voltage is between 9.0 volts and 19.0 volts.

### Conditions for Setting the DTC

The TCM detects 2 volts or less on the ignition 1 voltage circuit at the TCM for 6 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 commands the TCC OFF.

• | The TCM allows the vehicle to operate in transmission protection mode.

• | The TCM inhibits TU TD/MUMD operation.

### Conditions for Clearing the DTC

DTC P2534 is a Type A DTC.

### Diagnostic Aids

• | DTC P2534 detects a continuous open in the TCM ignition 1 switch circuit.

• | Observe the driver information center (DIC) messaging that would indicate the electrical system requires service.

• | Inspect for the following conditions:

- | Loose or damaged terminals at the generator

- | Loose or worn generator drive belt

• | Use the scan tool in order to inspect all other modules for voltage related DTCs.

• | Inspect the charging circuit for high resistance.

• | Inspect the vehicle battery for open or sulfated cells.

• | If all circuit tests are OK, ensure the transmission pass through connector and harness terminals are clean and not damaged.

### Reference Information

#### Schematic Reference

Automatic Transmission Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

• | Transmission General Description

• | Transmission Component and System Description

• | Electronic Component Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Engine ON, accessories OFF, measure and record the battery voltage at the battery terminals. The voltage should be between 12.0 and 15.0 volts.

⇒ | If the voltage is not within the specified range, refer to Charging System Test .

2. Increase the engine speed to 1,500 RPM. The Ignition Voltage parameter should remain between 12.0-14.5 volts.

⇒ | If the voltage is not within the specified range when the engine speed is increased, refer to Charging System Test .

3. Ignition ON, engine OFF, accessories OFF, observe the Battery Voltage parameter on the scan tool. The Battery Voltage should be between 12.0 and 14.5 volts.

⇒ | If the voltage is not within the specified range, refer to Charging System Test .

4. Engine ON, accessories OFF, observe the Ignition Voltage parameter on the scan tool. The Ignition Voltage should be between 12.0 and 14.5 volts.

⇒ | If the voltage is not within the specified range, refer to Charging System Test .

5. 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

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

1. Engine OFF, disconnect the TCM connector. Connect the negative probe of the DMM to a good ground. Turn ON the ignition, with the engine OFF, probe the battery positive voltage circuit, TCM connector terminal 1, and the ignition 1 voltage circuit, TCM connector terminal 12, on the harness side of the TCM 14-Way connector with the positive probe of the DMM. Measure the voltage for each circuit. The voltage should be between 11.0 and 14.5 volts.

⇒ | If the voltage is 0 volts, inspect the TRANS fuse, and the TCM fuse for being open. If open, test the affected circuit for a short to ground.

⇒ | If the fuse is not open, test the affected circuit for an open.

2. Compare the battery positive voltage value to the ignition 1 voltage value from above. The voltage drop between the circuits should be less than 0.5 volt.

⇒ | If the voltage drop is greater than 0.2 volt, repair the open or high resistance in the affected circuit.

3. If all circuits and connections test normal, replace the control solenoid (w/body and TCM) valve assembly.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

| Important: Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

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

• | Perform the Service Fast Learn Adapts following all transmission related repairs.