Taillights Shorting Out? & Code 24 Problems

[rusty79beast]

1991 stock K5, 350TBI, 700R4, etc. Here's the problem, when I turned on the lights the other day I heard something crackling and saw a little smoke coming from behind the light switch, and then quick turned it off to prevent any damage. I took the switch out and ruled the switch out as the possible culprit (I jumpered the wires on the harness that connects to the switch and the headlights(Yellow Wire) work if jumpered to the positive 12V, and the taillights/marker light (Brown Wire) short out if jumpered to positive 12V. Also my dash lights weren't working either. I then took the entire dash out and all looks well behind there. The turn signals/hazards work fine, but the taillights don't work. Therefore I believe I have it narrowed down to somewhere between the switch and the rear of the truck. Question is how do I troubleshoot it down to the culprit? Do you think that the brown wire somewhere is grounding out on something? I'm lost as to where to go from here.

One more question is that my check engine light came on and it reads a code 24, which I believe has something to do with the VSS, and to further diagnos this, the speedometer hasn't worked for awhile, so I'm thinking the problem might be a faulty VSS.

Any comments or suggestions would be a great help!!

 

[dyeager535]

If you can scan the vehicle, you can check the ECM to see if it's reading the correct speed when you are moving. Somewhat likely it's the VSS or *wiring* for the VSS if the speedo isn't working. I believe the needle should move to 0 on the gauge when you turn the key to run from off, which indicates it's at least getting power. Just can't remember if it goes to 0 when you turn the vehicle off, or if it just "floats" otherwise.

 

[rusty79beast]

I think I read somewhere that I can jack up the rear end and check for a increasing AC voltage at the sensor while I hit the gas in drive to see if thats the problem or not. Anyone heard of doing something like that to check the VSS?

 

[dyeager535]

I'd rather look at the input the ECM is using, voltage can be misleading (quick changes can be missed) and is probably quite low in the first place.

 

[rusty79beast]

Anybody have any way of troubleshooting my electrical problem? I'm lost and can't figure out how to go about finding the what I believe is a short. Please help

 

[dyeager535]

If you search, I've got a post with "troubleshooting" in the title that covers code troubleshooting. Not sure if 24 is listed or not, worth checking for.

 

[Tim L]

Do you have a trailer hitch hookup ? check for a short . Also I think the taillight wires go up through the rear quarters under the lights ,see if the grommit is still doing its job.

Tim

 

[rusty79beast]

Well I found 2 problems and corrected them. One of the problems was from me being a dumb*ss. When hooking up my cd player I for some stupid reason hooked up the ground and the old radio backround light wire (brown wire) to the ground of my cd player. It must've been dark and I thought they were both black but one was black and the other was dark brown. I take all the blame on that one. Now for the dash lights not working, the switch is half bad. The headlight position works great, but the marker light position of the switch doesn't work, therefore the dashlights which go through the rheostat on the switch didn't go on. Thanks for your help with the possible causes

Now tonight I'm going to tackle the speedometer issue and see if I can rule that the VSS is the culprit, and maybe find on at a junkyard since they are about $85 brand new from NAPA. Thanks again!