The Transfer Case Control Module (TCCM) monitors transfer case operation along with input and output information. If TCCM self-diagnostic system senses a failure or problem in the transfer case control system, a Diagnostic Trouble Code (DTC) will be stored in TCCM memory. Diagnostic trouble code can be retrieved for diagnosis of transfer case control system.
When ignition switch is in run position, TCCM tests whether RAM standby power (battery maintained power) to TCCM was lost since ignition was last turned off. When power is interrupted to TCCM (pin No. 6), TCCM stores loss of RAM standby power and sets DTC "1". If DTC "1" is present, check Orange wire circuit between TCCM and fuse block. Repair circuit as necessary. If Orange wire circuit is okay, replace TCCM.
During electronic shifting, TCCM checks motor/encoder for normal operation. If motor/encoder does not function properly, TCCM stores motor/encoder failure DTC "2". If DTC "2" is present, check circuits between TCCM and motor/encoder. If circuits are okay, replace motor/encoder. If circuits are repaired, perform TRANSFER CASE FUNCTIONAL TEST.
Each time electronic shift motor is turned on or off, TCCM tests whether motor functions properly. If motor does not function properly, TCCM stores motor link circuit failure DTC "3". Shift select buttons will blink to alert driver of problem. If DTC "3" is present, check circuits between TCCM and electric shift motor. If circuits are okay, replace electric shift motor. If circuits are repaired, perform TRANSFER CASE FUNCTIONAL TEST.
Each time ignition is turned on, TCCM tests memory, program and internal system to ensure TCCM is operating properly. If fault is detected in TCCM, it stores a RAM/ROM memory failure DTC "4". If DTC "4" is present, replace TCCM.
NOTE:Diagnostic Trouble Codes (DTCs) are displayed on 3 transfer case shift select buttons. When proper conditions are met, select buttons will blink to indicate DTC from "1" to "4".
Turn ignition off for at least 6 seconds. Locate DLC near right side of steering column. Install jumper wire between diagnostic pigtail (Orange wire at DLC terminal No. 13) and ground.
Turn ignition to run position (engine off). Observe shift select buttons. If all shift select buttons blink once at same time then stop, no DTCs are stored. If only one code is stored in TCCM memory, that code will blink repeatedly, with a 3 second delay between sequences. If more than one code is present, next code will flash after a 3 second delay, then sequence will repeat. Count number of blinks for each code. See Fig. 1.
Write down all DTCs. After retrieving DTCs. Clear TCCM memory and repeat procedure. See CLEARING DIAGNOSTIC TROUBLE CODES. If DTCs return, perform appropriate test. See DTC DEFINITIONS under SELF-DIAGNOSTIC SYSTEM.
Fig. 1: Reading Diagnostic Trouble Code
Courtesy of GENERAL MOTORS CORP.
CLEARING DIAGNOSTIC TROUBLE CODES
NOTE:DTCs will not be cleared if 20-amp T-case fuse is not removed for at least 30 seconds.
Turn ignition off. Remove T-CASE (20-amp) fuse from fuse block. Wait at least 40 seconds and reinstall fuse. Cycle ignition on and off 5 times. All DTCs will be cleared from TCCM memory.
Thursday, March 25th, 2010 AT 5:44 PM