Why are your back up lights on when you turn on the parking or head lights on a 1997 Chevy Suburban

Tiny
EPACHEVY
  • MEMBER
  • 1997 CHEVROLET SUBURBAN
  • 273,000 MILES
The reverse lights work normally when the parking or headlights are off but when the parking or headlights are turned on, the reverse lights are also on and fully bright. This is on a 1997 Chevy Suburban. I've cleaned the ground to the frame that is close to the wiring harness for the rear lights. I've pulled the four bulbs for the parking lights and the reverse lights remain lit - no change. I've heard about the rear light circuit board(s) but don't know where they are to remove and see if the problem persits. They are not any where on or around the tail light assembly.
Wednesday, January 4th, 2012 AT 11:42 PM

6 Replies

Tiny
FACTORYJACK
  • MECHANIC
  • 4,159 POSTS
The reverse lamps are powered from a direct feed off the transmission range switch, or backup lamp switch if it is a manual. Check that all the fuses are intact, to eliminate the possibility of backfeeding. The circuit boards are the taillamps themselves. To prove if this is true, look at the lamp assemblies. If there is one connector, and not individual sockets, then it is an assembly. I would suspect they are at fault.
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Thursday, January 5th, 2012 AT 12:00 AM
Tiny
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There is one wire connector and three lamp sockets per assembly - one lamp for reverse, two for parking/break. And both the right and left act the same. Are you saying the assembly where the lamps are installed needs to be replaced? Both right and left? - Or just one or the other? I did check continuity (with a meter) between each of the wires - brown, yellow, green, and black - and there is continuity between each all the wires - is this normal or confirmation that they are the problem? Thanks!
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Thursday, January 5th, 2012 AT 12:18 AM
Tiny
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Sorry - it's an automatic transmission. I did check the parking light fuse - only found it to be one that powers all three lamps.
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Thursday, January 5th, 2012 AT 12:19 AM
Tiny
FACTORYJACK
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That is what would be considered the circuit board. Since both lamps are lighting, I would do a bit more diagnosing. It looks like light green is the reverse lamp power from the PRNDL switch. If you remove that wire from one assembly, or both, and the lights are still on, then it is circuit board. It is probably easier to cut the wire, but if you can get the terminal out of the connector block, then do that.
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Thursday, January 5th, 2012 AT 1:00 AM
Tiny
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That doesn't appear to work to solve the problem. Is the PRNDL switch the one in the steering column? If so, what are the chances that the problem lies there? I just started having a problem with the right rear turn signal - I get a double speed blinking rate which can indication the rear buld is out but it's not. I also moved this assembly to the left side and it worked as it was supposed to. Another recent problem with the turn signals is the turn signal sound randomly is turned on but the dashboard arrow and the turn signal lamps are not lit so it's only the sound. If this switch makes sense as to the problem - how easy is it to replace? Thanks.
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Saturday, January 7th, 2012 AT 12:43 AM
Tiny
FACTORYJACK
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The PRNDL switch used to be located on the column, on older models. I believe it is located at the transmission, where the cable connects to the shift shaft lever. The PRNDL would have no effect on turn signal concerns. The fast blink is not necessarily just an indicator that the rear bulb is out, any of the turn bulbs can be out.
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Saturday, January 7th, 2012 AT 3:11 AM

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