For 1990-2009 cars

### Circuit 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.

If the TCM detects low voltage on the Ignition 1 voltage circuit, DTC P2534 sets. DTC 2534 is a type A DTC.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2534 Ignition 1 Switch Circuit Low Voltage

### Conditions for Running the DTC

• | The ECM sends the information of engine run status to the TCM.

• | No TCM diagnostic reset.

### Conditions for Setting the DTC

The TCM detects an open or short to ground on the Ignition 1 voltage circuit and conditions are present more than 400 out of 480 samples occur.

### Action Taken When the DTC Sets

• | The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL).

• | The TCM commands maximum line pressure.

• | The TCM commands 2nd gear.

• | The TCM freezes transmission adaptive functions.

• | At the time of the failure, the TCM records the operation conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.

• | At the time of the failure, the ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame.

### Conditions for Clearing the DTC

• | The TCM turns OFF the MIL after the third consecutive trip in which the diagnostic test runs and passes.

• | A scan tool can clear the DTC.

• | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occuring.

• | The TCM cancels the DTC default actions when the ignition is OFF long enough in order to power down the TCM.

### Conditions for Clearing the DTC

• | The ECM turns off the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.

• | A scan tool can clear the DTC.

• | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emmission-related diagnostic fault occurring.

• | The TCM cancels the DTC default actions when the ignition is OFF long enough in order to power down the TCM.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Install a scan tool.
2. Turn ON the ignition with the engine OFF.

Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the TCM.

3. Record the DTC Freeze Frame and Failure Records.
4. Clear the DTC.

Does DTC 2534 reset?

--

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3 |

1. Remove the TRANS fuse.
2. Inspect the fuse for an open. Refer to Circuit Protection - Fuses .

Did you find the condition?

--

Go to Step 4

Go to Step 5

4 | Test the ignition 1 voltage circuit of the TCM for a short to ground between the underhood fuse block and the TCM. Refer to Testing for Short to Ground and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 7 | --
5 | Test the ignition 1 voltage circuit of the TCM for an open between the underhood fuse block and the TCM. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 6
6 | Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 7 | --
7 | Perform the following procedures in order to verify the repair:

1. Select the DTC.
2. Select Clear Info.
3. Start the vehicle.
4. Select Specific DTC.
5. Enter DTC P2534.

Has the test run and passed?

--

Go to Step 8

Go to Step 2

8 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK