ATCM Fault Codes

Turn ignition on. DO NOT start engine. Depress OD switch on shift lever to ON position.
NOTE: Fault codes can only be retrieved with OD switch in ON position. If OD switch is in OFF position, OD OFF light will not blink the fault code.
Locate check connector near left strut tower in engine compartment. See Fig 1 . Install fused jumper wire between cavities No. 3 and 17 of check connector. See Fig 1 .
Note number of blinks from OD OFF light on instrument panel. If normal system operation exists, OD OFF light will blink once every .25 second. See Fig 2 .
If system is operating correctly and no fault code exists, turn ignition off and remove fused jumper wire. Check system by the symptom. See appropriate symptom under SYMPTOM TROUBLESHOOTING .
If fault code exists, OD OFF light will blink once every .5 second. The number of blinks will equal the first digit of fault code. After a pause of 1.5 seconds, the second digit will be displayed. See Fig 2 .
If more than one fault code exists, the next fault code will be displayed after pause of 2.5 seconds. See Fig 2 . Smallest value fault code will be first and then continue to the largest fault code. Fault codes will be repeated.
Once fault code is obtained, determine probable cause. See FAULT CODE IDENTIFICATION table. For trouble shooting of fault codes, see FAULT CODE TROUBLE SHOOTING . Turn ignition off and remove fused jumper wire.

NOTE: Once repairs have been performed, fault codes must be cleared from ATCM memory. See CLEARING FAULT CODES under TRANSMISSION TESTING.

FAULT CODE IDENTIFICATION

Fault Code

⁽¹⁾ Probable Cause

⁽²⁾ Defective No. 1 Speed Sensor

⁽³⁾ Defective No. 2 Speed Sensor

Defective No. 1 Solenoid

Defective No. 2 Solenoid

Defective Lock-Up Solenoid

⁽¹⁾	Check listed component for probable cause. Also check wiring and connections of specified component.

⁽²⁾	No. 1 speed sensor is located on instrument panel.

⁽³⁾	No. 2 speed sensor is located on transmission.

Fig 1: Identifying Check Connector Terminals

Courtesy of GENERAL MOTORS CORP.

Fig 2: Identifying Fault Code Displays (1 of 2)

Courtesy of GENERAL MOTORS CORP.

Fig 3: Identifying Fault Code Displays (2 of 2)

Courtesy of GENERAL MOTORS CORP.