Reading Diagnostic Trouble Codes

When the Transmission Control Module (TCM) senses an abnormality in the input or output systems, the D4 Indicator Light in the Gauge Assembly will blink.




When the Service Check Connector (located behind the Center Console) is connected with a Special Tool, the D4 Indicator Light will blink the Diagnostic Trouble Code (DTC) when the Ignition Switch is turned "ON".

When the D4 Indicator Light has been reported on, connect the Service Check Connector with the Special Tool. Then turn on the Ignition Switch and observe the D4 Indicator Light.




Codes 1 through 9 are indicated by individual short blinks, codes 10 through 15 are indicated by a series of long and short blinks. One long blink equals 10 short blinks. Add the long and short blinks together to determine the code. After determining the code, refer to the Diagnosis by Symptoms.

Some Programed Fuel Injection (PGM-FI) problems will also make the D4 Indicator Light come on. After repairing the PGM-FI system, disconnect the BACK UP fuse (7.5 A) in the Under-Hood Fuse/Relay Box for more than 10 seconds to reset the TCM memory, then recheck.

NOTE: Disconnecting the BACK UP fuse also cancels the Radio Anti-theft code, preset stations and the Clock setting. Get the customer's code number and make note of the radio presets before removing the fuse so you can reset them.

Supplemental Restraint System (SRS) Components are located in this area. Review the SRS Component locations, precautions, and procedures in the Air Bags (SRS) section before performing repairs or service.

1. Remove the left heater lower cover.
2. Pull the carpet back to expose the Engine Control Module (ECM) cover.




3. Remove the ECM cover mounting nuts, and turn the TCM over.
4. Inspect the circuit on the TCM according to the Troubleshooting Flowchart with the Special Tools and a Digital Multimeter.


How to use the Backprobe Set




Connect the Backprobe Adapters to the Stacking Patch Cords, and connect the cords to a Multimeter. Using the wire insulation as a guide for the contoured tip of the Backprobe Adapter, gently slide the tip into the Connector from the wire side until it comes in contact with the Terminal end of the wire.


Final Procedure

NOTE: This procedure must be done after any troubleshooting.

1. Turn the Ignition Switch "OFF".
2. Remove the Special Tool from the Service Check Connector.
3. Reset the TCM.
4. Turn the Ignition Switch "ON".
5. Enter the Anti-Theft Code for the Radio, then enter the customer's Radio station presets.