C4 brake light issue
Thread Starter
2nd Gear
Joined: Aug 2014
Posts: 2
Likes: 0
From: Port Orchard WA
C4 brake light issue
I seem to have an issue with my 1995 C4 conv. All 5 lights work when in park (AutoTrans). In other gears only the 3rd light works. The Main round lights do not. Any suggestions what to check? Thanks, Bill
Team Owner
Joined: Sep 2003
Posts: 25,398
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The stop light switch (SLS), the brake/transmission solenoid interrupt (BTSI) and the transmission position switch (NSS) are all related. Do your back-up lights work as they should in reverse? Do you need to depress the button on the transmission AND foot on brake to shift out of park? Does the car start in both neutral and park?
The SLS has a separate function for TCC/BTSI function so I'd likely start at the SLS and I don't know just how I'd attempt to diagnose. The PCM is involved also. There would be a purple wire at the SLS and I believe with out the brake pedal applied there should be power to it, pedal depressed it should loose power. If it were mine I'd start there. The SLS isn't as inexpensive as the earlier years so it might be a gamble to just buy and replace. I'm quite sure the SLS has 3 connectors on it 2 - 2 wire and one 4 wire. The purple should be on one of the 2 wire.
GM # 10211657 is the part number.
Do you have a FSM (Factory Service Manual)?
The CHMSL is supplied power from a separate wire spliced into the wire that feeds the other four from the directional signal switch. That explains why the CHMSL works as requested.
It's I believe a rather unusual circumstance. Good luck!
What happens with "no key" or "key off' when you apply the brake pedal?
The SLS has a separate function for TCC/BTSI function so I'd likely start at the SLS and I don't know just how I'd attempt to diagnose. The PCM is involved also. There would be a purple wire at the SLS and I believe with out the brake pedal applied there should be power to it, pedal depressed it should loose power. If it were mine I'd start there. The SLS isn't as inexpensive as the earlier years so it might be a gamble to just buy and replace. I'm quite sure the SLS has 3 connectors on it 2 - 2 wire and one 4 wire. The purple should be on one of the 2 wire.
GM # 10211657 is the part number.
Do you have a FSM (Factory Service Manual)?
The CHMSL is supplied power from a separate wire spliced into the wire that feeds the other four from the directional signal switch. That explains why the CHMSL works as requested.
It's I believe a rather unusual circumstance. Good luck!
What happens with "no key" or "key off' when you apply the brake pedal?
Last edited by WVZR-1; Aug 25, 2014 at 09:07 PM.
Thread Starter
2nd Gear
Joined: Aug 2014
Posts: 2
Likes: 0
From: Port Orchard WA
Well, I thought I would order the brake peddle switch, so I did. Fiddled with the BPS and the light switch by the turn signal switch. Kinda moved the gear shift selector back and forth.
Without replacing the BPS it started working again. Strangest thing.
I am keeping the GM # 10211657 for future use.
Thanks for your comments.
Without replacing the BPS it started working again. Strangest thing.
I am keeping the GM # 10211657 for future use.
Thanks for your comments.
