Code 51 - Pass-Key Detection Invalid Key Detection
- Before proceeding, see PRELIMINARY CHECKS FOR CODES 51-54 under CCM ON-BOARD DIAGNOSTICS. If keys do work, proceed to next step to determine if keys or ignition lock cylinder is defective.
- Using Pass-Key Interrogator (J-35628-A), determine key code number. Connect jumper between ALDL terminals "G" (CCM) and "A" (ground). See Figure. Turn ignition on.
- Press TRIP/ODO button until "1.2" displays on trip monitor. See Figure. Press ENG/MET button until "06xxx" displays on odometer, with xxx being a number from 33 to 213. Note xxx number and use to determine key code number. See KEY CODE IDENTIFICATION table.
KEY CODE IDENTIFICATION
| Number |
Key Code |
| 33-38 |
1 |
| 42-47 |
2 |
| 52-58 |
3 |
| 64-70 |
4 |
| 76-83 |
5 |
| 91-98 |
6 |
| 106-113 |
7 |
| 121-128 |
8 |
| 136-143 |
9 |
| 149-156 |
10 |
| 164-170 |
11 |
| 177-183 |
12 |
| 188-194 |
13 |
| 199-204 |
14 |
| 208-213 |
15 |
- If key code from table matches key code found using PASS-Key Interrogator, system is functioning properly. For possible intermittent problems, see PRELIMINARY CHECKS FOR CODES 51-54 under CCM ON-BOARD DIAGNOSTICS.
- If key codes do not match, check for Code 52 and/or 53 to be set. If either of these other codes are set, repair problems causing Code 52 and/or 53 to set. Clear codes and check if Code 51 resets. If Code 51 resets, go to step 2) and repeat test.
- If Code 52 and/or 53 are not set, disconnect ignition lock cylinder connector at base of steering column. Using Terminal Adapter Kit (J-35616), connect DVOM between White/Black wire terminal of ignition lock cylinder connector (CCM harness side) and ground. See Fig 1. Turn ignition on.
- If voltage is between 4.9-5.1 volts, go to step 9). If voltage is not between 4.9-5.1 volts, using Terminal Adapter Kit (J-35616) and DVOM, backprobe between White/Black wire terminal of CCM Green connector and ground.
- If voltage is between 4.9-5.1 volts, check White/Black wire for shorts, open or poor connection between CCM Green connector and ignition lock cylinder. Repair or replace as necessary. If voltage is not between 4.9-5.1 volts, check for poor connection at White/Black wire terminal of CCM Green connector. If connection is okay, replace CCM.
- If voltage is between 4.9-5.1 volts with DVOM between White/Black wire terminal of ignition lock cylinder connector (CCM harness side) and ground, backprobe between White/Black wire terminals of ignition lock cylinder connector and CCM Green connector using Terminal Adapter Kit (J-35616) and DVOM.
- If continuity is present, check for possible intermittent. See PRELIMINARY CHECKS FOR CODES 51-54 under CCM ON-BOARD DIAGNOSTICS. If continuity is not present, repair Purple/White wire or poor connection between Purple/White wire terminal of CCM Green connector and Purple/White wire terminal of ignition lock cylinder connector. If Purple/White wire and connections are okay, replace CCM.
Courtesy of GENERAL MOTORS CORP.