For 1990-2009 cars

### Circuit Description

The transmission control module (TCM) supplies 5 volts to the EBCM via the TCC retarder output control circuit. The EBCM grounds the TCC retarder output control circuit when rear wheel slip is detected in order to command the TCM to disengage the torque converter clutch. Feedback voltage to the TCM is low when ground is applied to the TCC retarder output control circuit.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

The EBCM detects the TCC retarder output control circuit is open, shorted to ground or shorted to voltage.

### Action Taken When the DTC Sets

#### TCC retarder output control circuit open or shorted to voltage

• | The PRIMARY BRAKE indicator may turn ON.

• | The torque converter clutch remains locked during rear wheel slip, causing loss of stability.

#### TCC retarder output control circuit shorted to ground

• | The PRIMARY BRAKE indicator may turn ON.

• | The torque converter clutch is disabled, causing a reduction in fuel economy.

### Conditions for Clearing the DTC

The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.

### Diagnostic Aids

Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to the following:

• | Testing for Electrical Intermittents

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

• | Connector Repairs

### Test Description

The number below refers to the step number on the diagnostic table:

1. The EBCM may be damaged if the TCC retarder output control circuit is shorted to voltage.

2. The EBCM may be damaged if the TCC retarder output control circuit is shorted to 5 volts.

Step | Action | Value | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Antilock Brake System Schematics
1 | Did you perform the ABS diagnostic system check? | -- | Go to Step 2 | Go to Diagnostic System Check - ABS
2 |

1. Use a scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 5 seconds.
3. Turn ON the ignition and observe the scan tool.

Does the DTC set?

--

Go to Step 3

Go to Diagnostic Aids

3 |

1. Turn OFF the ignition.
2. Disconnect from the EBCM, the harness connector containing the TCC retarder output control circuit.
3. Turn ON the ignition.
4. Use a DMM in order to measure the voltage on the TCC retarder output control circuit.

Does the voltage measure within the range specified?

4.5-5.5 V

Go to Step 4

Go to Step 5

4 | Use a 3A fused jumper wire in order to connect the TCC retarder output control circuit to a good ground. Does the fuse in the jumper wire open? | -- | Go to Step 6 | Go to Step 9
5 | Test the TCC retarder output control circuit for an open, a short to ground or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 7
6 | Test the TCC retarder output control circuit for a short to 5 volts. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8
7 | Inspect for poor connections at the harness connector of the TCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8
8 | Concern is related to the transmission control module. Refer to Transmission Control Diagnostics for Allison automatic Transmission. Did you find and correct the condition? | -- | Go to Step 11 | --
9 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10
10 | Important: Following EBCM replacement, use the scan tool to perform the Tire Size Calibration procedure and the Trim Level Calibration procedure. Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the replacement? | -- | Go to Step 11 | --
11 |

1. Use the scan tool in order to clear the DTC.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 3

System OK