Code 41 (Powertrain Control Module (PCM) Serial Data Loss Of Communications)
- A short on serial data link circuit will disable entire link. An open will disable only those devices which become open-circuited. If Code 41 is present, trip computer will be inoperative, Heater-Vent-Air Conditioning (HVAC) electronic A/C-heater control head display will flash OFF and CHECK GAUGES function will not work. When Code 41 sets, it will also prohibit FEDS fuel enable from taking place. See CODE 54.
- Connect jumper wire between Data Link Connector (DLC) terminals No. 12 and 5. See Figure
. Turn ignition on. Press TRIP RESET button until "4.1" appears on trip monitor. See Figure
.
- If "Err" does not display in speedometer, system is functioning properly. Recheck step 1) again for telltale signs. Check for Powertrain Control Module (PCM) Code 51, which will also set a Code 41.
- If "Err" displays in speedometer, turn ignition off. Disconnect PCM connector and CCM Green connector. Using Terminal Adapter Kit (J-35616), connect DVOM between terminal E13 (Tan wire) of CCM Green connector and terminal D4 (Tan wire) of ECM Brown connector. Check for continuity. See Fig 1
.
- If continuity is not present, repair open in Tan wire between terminal D4 of ECM Brown connector and terminal E13 of CCM Green connector. If continuity is present, use terminal adapter kit to connect DVOM between terminal F12 (Tan wire) of CCM Green connector and terminal D4 (Tan wire) of PCM connector.
- If continuity is not present, repair open in Tan wire between terminal D4 of PCM connector and terminal F12 of CCM Green connector. If continuity is present, use terminal adapter kit to connect DVOM between terminal E13 (Tan wire) of CCM Green connector and ground. See Fig 1
.
- If continuity is present, repair short to ground in Tan wire between terminal E13 of CCM Green connector and PCM. If continuity is not present between terminal E13 (Tan wire) of CCM Green connector and ground, use terminal adapter kit to connect test light between terminal E13 (Tan wire) of CCM Green connector and ground. Turn ignition on.
- If test light comes on, repair short to battery voltage in Tan wire between terminal E13 of CCM Green connector and PCM. If test light does not light, repeat steps 4) through 6), except use terminal D15 (Tan wire) of ECM Brown connector instead of terminal D4 of ECM Brown connector. If system is still not functioning properly, wiggle connections to check for intermittent problems in Tan wire. When repairs are completed, clear codes and verify operation.
Courtesy of GENERAL MOTORS CORP.