Another reverse lights question
Thread Starter
Drifting
Joined: Mar 2005
Posts: 1,336
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From: North Canton OH
Another reverse lights question
Ok, did the searches. MN6, no reverse lights.
We can manually trip the #38 relay under the hood and the lights will come on.
All fuses (all of them) are good. Especially #2 under hood and #21 under foot well.
Have replaced the tranny switch.
Have pulled the plug and shorted the harness....
Then #21 blew.
What do the experts think of this one?
We can manually trip the #38 relay under the hood and the lights will come on.
All fuses (all of them) are good. Especially #2 under hood and #21 under foot well.
Have replaced the tranny switch.
Have pulled the plug and shorted the harness....
Then #21 blew.
What do the experts think of this one?
Tech Contributor
Joined: Dec 2003
Posts: 19,384
Likes: 87
From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
That one's got me stumped at present. I guess its possible that the new transmission switch was bad. I've had that before. I fitted a new one to the Camaro and like you the fuse was still blowing. It turned out to be a bad switch. The clue was it blew as I selected reverse.
Here's the wiring diagram which may help troubleshoot. I'll look in the book to see if there's any help there
Here's the wiring diagram which may help troubleshoot. I'll look in the book to see if there's any help there
Last edited by DeeGee; Mar 13, 2010 at 01:46 AM.
Thread Starter
Drifting
Joined: Mar 2005
Posts: 1,336
Likes: 0
From: North Canton OH
Thanks for that, I'll have a look and was thinking along the same lines.
My question is, why does shorting the connector blow the fuse at all? Isn't that what the switch does when its working normally by closing the circuit?
My question is, why does shorting the connector blow the fuse at all? Isn't that what the switch does when its working normally by closing the circuit?
Team Owner
Joined: May 2001
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From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Have you tried swapping out relay #38 with another one in the fuse panel up front? Just find one with the same shape/size and part number on it and try it out. None of those four pin micro-relays are polarized so they will work when plugged in either way.
Team Owner
Joined: Jul 2006
Posts: 22,202
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From: Kannapolis NC
Tripping the relay gets the 12 volts to the lights through a different always hot source that operates the approach lights, so that's normal. It tells you that the lights and grounds are good. Measure on the brown wire at the transmission switch with key on for 12 volts. If it's there, your supply and fuse are good. Measure on the gray wire with the key on and car in reverse. If you have 12 volts there, your switch is good. If the fuse blows at this point, either the switch is shorted or you have a short in the gray wire going up to relay 38. The reason I say shorted is you said when you bypass the connector at the transmission fuse 21 blows, if I read correctly. You should be able to disconnect the plug on the transmission, short the gray and brown together with the key on and get backup lights. If the fuse is blowing when you do this, we are back to something shorted after the switch but before the relay. That only leaves the gray wire as a possibility. The schematic shows C140 in that line. Post what you find when you do any of these checks.
Team Owner
Joined: May 2001
Posts: 36,836
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From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Now I'm wondering if the Gray wire (circuit 1524) in the B/U lamp switch harness is shorted to ground either constantly or intermittently Have you checked backwards on this to see if there are any signs of chaffing, burns, cuts, abrasions, etc?
Also looking at possible short in that same circuit leg (1524) going to the EBTCM.
A short in either of those two legs of 1524 would cause current to go straight to ground before it ever gets to the bulbs. Also, like Dave said, if there is an internal short in the B/U lamp switch body to ground, that would pop fuse 21 too. Maybe pull the switch and check for continuity between each of the connecter pins to the body/housing of the switch would be worthwhile too.
Also looking at possible short in that same circuit leg (1524) going to the EBTCM.
A short in either of those two legs of 1524 would cause current to go straight to ground before it ever gets to the bulbs. Also, like Dave said, if there is an internal short in the B/U lamp switch body to ground, that would pop fuse 21 too. Maybe pull the switch and check for continuity between each of the connecter pins to the body/housing of the switch would be worthwhile too.
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Team Owner
Joined: May 2001
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From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Tripping the relay gets the 12 volts to the lights through a different always hot source that operates the approach lights, so that's normal. It tells you that the lights and grounds are good. Measure on the brown wire at the transmission switch with key on for 12 volts. If it's there, your supply and fuse are good. Measure on the gray wire with the key on and car in reverse. If you have 12 volts there, your switch is good. If the fuse blows at this point, either the switch is shorted or you have a short in the gray wire going up to relay 38. The reason I say shorted is you said when you bypass the connector at the transmission fuse 21 blows, if I read correctly. You should be able to disconnect the plug on the transmission, short the gray and brown together with the key on and get backup lights. If the fuse is blowing when you do this, we are back to something shorted after the switch but before the relay. That only leaves the gray wire as a possibility. The schematic shows C140 in that line. Post what you find when you do any of these checks.
Looks like we're both on the same track though.
Thread Starter
Drifting
Joined: Mar 2005
Posts: 1,336
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From: North Canton OH
I suppose there is a possibility I shorted my jumper to the exhaust or tranny, it was pretty rough being under there with the car only on jack stands.
At any rate, your help has been great. I sold the car, so I've forwarded this post to the new owner. I let him know this was an issue before he accepted the transaction, so hopefully he gets it sorted out with VERY little cost/struggles.
Good luck Scott!
At any rate, your help has been great. I sold the car, so I've forwarded this post to the new owner. I let him know this was an issue before he accepted the transaction, so hopefully he gets it sorted out with VERY little cost/struggles.
Good luck Scott!
