DTC B1970, Exterior Light Power Fault: Testing
- If BCM system check was performed, go to next step. If BCM system check was not performed, go to BCM SYSTEM CHECK
.
- Remove low beam relay from relay box located under dash. See Fig 1
. Connect DVOM leads between low beam relay terminal No. 3 (Red/White wire) at relay box and ground. Connect scan tool. Select EXTERIOR LAMPS from light test menu in Special Functions. While commanding exterior lights on and off, check voltage reading. Voltage should change as commanded, and battery voltage should exist when exterior lights are on. If voltage is as specified, go to next step. If voltage is not as specified, go to step 4).
- Check for poor connection at BCM 32-pin, connector C2, terminal B10 (Red/White wire). Check all BCM power and ground circuits. See WIRING DIAGRAM
. Using scan tool, clear codes. Check for codes. If DTC B1970 is set, go to step 5). If DTC B1970 is not set, go to BCM SYSTEM CHECK
.
- Remove parking light relay from relay box located under dash. See Fig 1
. Disconnect BCM 32-pin C2 connector. Using DVOM, check resistance between low beam relay terminal No. 3 (Red/White wire) at relay box and ground. If resistance is infinite, go to step 6). If resistance is not infinite, go to step 7).
- Replace BCM. Perform BCM SYSTEM CHECK
.
- Leave DVOM connected as specified in step 4). While observing DVOM, wiggle wires between BCM and relay box. If DVOM indicates as short to ground, go to next step. If DVOM does not indicate a short to ground, go to step 3).
- Repair short to ground in Red/White wire between BCM, parking light relay and low beam relay. Perform BCM SYSTEM CHECK
.
Courtesy of GENERAL MOTORS CORP.