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Help me with this wiring schematic. Am I a dumb-dumb? (don't answer that! )
Or is this wiring schematic wrong. Someone tell my why the rear brake lights don't work, with the brake relay removed? The CHMSL illuminates....but the rear brake lights do not. Why not?
Yep. It LOOKS, like it gets power from both; straight through the stop switch, and also through the relay. CHMSL gets it only through the brake switch/white wires.
..... Is this a truck ? If so , there is a breakout indicated just after the stop light switch for cruise and CMHSL ... I would suggest that the white wire beyond the breakout to A1 on the turn signal is not there (trucks) or is open ... without the relay there is no power to lt blu E2 term on the turn signal switch ... so , no power to the brake light circuit .....
It IS. '98 1500. My tail brake lights went out, looked up ^that schematic to diagnose. Problem was a bad connection at the relay plug. But the schematic didn't "jive" with what was happening in the truck.
In my mind, that white wire from the junction to A1 shouldn't be in the schematic. With that wire in place, lights should work w/o the relay.
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Last edited by Tom400CFI; Jul 28, 2021 at 10:10 AM.
Help me with this wiring schematic. Am I a dumb-dumb? (don't answer that! )
Or is this wiring schematic wrong. Someone tell my why the rear brake lights don't work, with the brake relay removed? The CHMSL illuminates....but the rear brake lights do not. Why not?
CHMSL does not have to work in unison with turn signals
The diagram you found does not note these exceptions.
The trucks have the relay.
Suburban Utility have the white wire connection at A1.
That would explain it. That is BFS. I hate that crap. The Schematic is screen shot'ed right off of Mitchell/Ondemand5. Which I pay for. I hate it when you pay for tools, and you get....ambiguity. NO one needs that when diagnosing b/c then you have to resort to guessing and intuition, which is no better than having NO tools. Grrrr.
While this wasn't a big deal, it's a confidence breaker in the tool/tools. It's like having a scan tool (a good one with the latest updates) that still won't read/actuate/test SOME things....you get to where you're not sure if you are doing it wrong? Or the tool won't do it? Annoying. And that was the case here. BS.
In 1998 GM was still.using paper manuals. It is possible there was a "Service Manual Update" similar to a tsb correcting errors in manuals. If final edition was already printed; correction won't appear in manual. The update is to be attached to manual in appropriate section. In 2000 GM went primarily to online manuals which stay current.
IDK that alldata will copy, paste or edit pages for updates.
Wiring schematic reading pros....
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