91 Jimmy, was told I had the left brake light out. Went to change it, but the bulb looked fine; blinker works fine (on the left side). Swapped the bulb from the right side to the left side, same thing - No brake light, but the turn/brake light filament works when it's plugged in on the left side. Marker lamp (the small bulb) and tail lights work fine on both sides.
A few months back after replacing the RWAL computer (GM manual trouble tree said to after diagnosing), I had a RWAL Code 10, which has something to do with the brake light switch circuit. Had a mechanic look at it and the found a trace on some diode that is associated with the brake system had blown. They fixed it and I haven't gotten any RWAL codes since.
I've checked the taillight grounds and I have continuity from the bulb holder contacts to the ground. The fact that the blinker works (at least on the left rear) makes me skeptical of the wiring since the brake light and turn signal light both use that same power feed and filament. So I tried diagnosing the brake switch, first by jumping the purple and pink wires at the switch. I got voltage at the connector, but still no brake lights (I'm assuming jumping those wires would eliminate the switch and the lights should come on). There's an additional connector on the brake switch with an orange wire and a white wire. Looking through the wiring manual, I can't seem to find where these wires go or what their purpose is. Maybe they also need be jumped? The troubleshooting steps in the books really aren't very helpful in describing the function of that diode or the wires at the brake switch, other that the pink and purple wires form a circuit when the switch is closed.
For the reverse lights, I ran through the trouble tree and verified voltage on the green wire at the backup lamp switch and no voltage on the blue wire when shifted in reverse. I adjusting the switch one click at a time while in reverse and jiggling the shifter at each adjustment, still nothing. Verified bulbs were good, and ground between the bulb socket and body ground. My guess is it's probably just the switch, but I'd like the make sure before I pull half the dash apart to fix it.
A few months back after replacing the RWAL computer (GM manual trouble tree said to after diagnosing), I had a RWAL Code 10, which has something to do with the brake light switch circuit. Had a mechanic look at it and the found a trace on some diode that is associated with the brake system had blown. They fixed it and I haven't gotten any RWAL codes since.
I've checked the taillight grounds and I have continuity from the bulb holder contacts to the ground. The fact that the blinker works (at least on the left rear) makes me skeptical of the wiring since the brake light and turn signal light both use that same power feed and filament. So I tried diagnosing the brake switch, first by jumping the purple and pink wires at the switch. I got voltage at the connector, but still no brake lights (I'm assuming jumping those wires would eliminate the switch and the lights should come on). There's an additional connector on the brake switch with an orange wire and a white wire. Looking through the wiring manual, I can't seem to find where these wires go or what their purpose is. Maybe they also need be jumped? The troubleshooting steps in the books really aren't very helpful in describing the function of that diode or the wires at the brake switch, other that the pink and purple wires form a circuit when the switch is closed.
For the reverse lights, I ran through the trouble tree and verified voltage on the green wire at the backup lamp switch and no voltage on the blue wire when shifted in reverse. I adjusting the switch one click at a time while in reverse and jiggling the shifter at each adjustment, still nothing. Verified bulbs were good, and ground between the bulb socket and body ground. My guess is it's probably just the switch, but I'd like the make sure before I pull half the dash apart to fix it.
