electrical gremlins 04 sb

[ImpalaSlayer]

i have my old car here for a few fixes and i cant seem to figure them out.

problems are:

brake lights dont work
shifter very hard to "unlock"
turnsignals/hazards dont work

ive checked the fuses 12 and 19, they read good on a multi meter but look kinda weird on top. i should also mention fuse 6 looks the same way but checks good with a multimeter.

fuse 12 is reads: Multi-function switch for turn/hazard lamps

fuse 19 read: Brake lamps

fuse 6 reads:

Instrument cluster warning lamps module, Overdrive control switch, Lighting Control Module (LCM), Police vehicle option

i pulled the brake light switch off the pedal (both of them), it opens and closes like it should. i even pressed the switch while it was off the pedal to see if it lit the brakes, no dice.

Kirk told me all this seemed to happen in one night, im not even sure he knew the brake lights wernt working.

could this be the LCM? if not any other ideas?

[ctrlraven]

My first guess would of been the brake light switch for the brake lights and turn signals/hazards. The other switch on the brake should be the shift interlock switch which could have something to do with the shifter being very hard to take out of park. Switches should be fairly cheap. I would try replacing them.

[fastblackmerc]

i have my old car here for a few fixes and i cant seem to figure them out.

problems are:

brake lights dont work
shifter very hard to "unlock"
turnsignals/hazards dont work

ive checked the fuses 12 and 19, they read good on a multi meter but look kinda weird on top. i should also mention fuse 6 looks the same way but checks good with a multimeter.

fuse 12 is reads: Multi-function switch for turn/hazard lamps

fuse 19 read: Brake lamps

fuse 6 reads:

Instrument cluster warning lamps module, Overdrive control switch, Lighting Control Module (LCM), Police vehicle option

i pulled the brake light switch off the pedal (both of them), it opens and closes like it should. i even pressed the switch while it was off the pedal to see if it lit the brakes, no dice.

Kirk told me all this seemed to happen in one night, im not even sure he knew the brake lights wernt working.

could this be the LCM? if not any other ideas?

Brake lights don't go through the LCM. They are the only lights that do not go through the LCM.

When you had the switch off the pedal (there should only be one) did you check power going to the switch and power on the other connector when you closed the switch. If you have power on one side of the switch you can jump the connectors to see if the brake lights work.

If the brake light switch doesn't work you'll never get the car out of PARK since there is an interlock that prevents moving the gearshift out of PARK unless the brake pedal is depressed.

Try replacing the fuses as they are cheap.

[ImpalaSlayer]

My first guess would of been the brake light switch for the brake lights and turn signals/hazards. The other switch on the brake should be the shift interlock switch which could have something to do with the shifter being very hard to take out of park. Switches should be fairly cheap. I would try replacing them.
the second one is for cruise control. they both check out on the volt meter

[ImpalaSlayer]

Brake lights don't go through the LCM. They are the only lights that do not go through the LCM.

good to know, wont waste my time there then

When you had the switch off the pedal (there should only be one) did you check power going to the switch and power on the other connector when you closed the switch. If you have power on one side of the switch you can jump the connectors to see if the brake lights work.

there are clearly 2 switches that work with the brake, one for cruise control, one for the brake lights. ill have to check for power and try to jump it.

If the brake light switch doesn't work you'll never get the car out of PARK since there is an interlock that prevents moving the gearshift out of PARK unless the brake pedal is depressed.

i understand this, thats why i went after the switch int he first place. it wasnt untill i started messing with it that i noticed the lights wernt working either

Try replacing the fuses as they are cheap.

ill go back out and check for power now

[ImpalaSlayer]

just checked for power at the switch, no dice. fuse in that slot is good :wtf:

[BODYMAN]

if no power to the switch and fuse is good sounds like wire has chaffing somewere and if the case it can be a pain to find were its causing the lose,dont think it would be cause a bad ground somewere

[DEFYANT]

I had a power gremlin once also. Turned out to be the power wire in the driver side sun visor twisted and frayed causing a short. Thanks to Carfixer for that helpful hint. Apparently a few 04s had that problem.

[fastblackmerc]

just checked for power at the switch, no dice. fuse in that slot is good :wtf:

See if you have power to the contact for the fuse, if good replace that fuse.

[fastblackmerc]

if no power to the switch and fuse is good sounds like wire has chaffing somewere and if the case it can be a pain to find were its causing the lose,dont think it would be cause a bad ground somewere

If the wires was chaffing you'd be blowing the fuse.... no?

[Got_1]

check fuses with a test light. a tiny strand of wire can carry 12 volts but will not be able to support any amperage. a test light will add an additional load and tell you if the fuse is actually good or not.

This may not be your issue but its a good habit to get into.

you didn't mention that you checked fuse 22 at the CJB. that is hot at all times and directly feeds the multifunction switch and brake switch.

[RF Overlord]

you didn't mention that you checked fuse 22 at the CJB. that is hot at all times and directly feeds the multifunction switch and brake switch.That does seem to be the only fuse that has all the described issues in common, but it also supplies power to the ABS module and the PCM, for what exact functions I don't know, but I would think there would be other symptoms... :dunno:

[hwy73]

Since this seems to be falling into the category of "gremlin", I am going to throw this out based on experience. On the P71's, more than once the hazard flasher switch on the top of the steering column would act up (probably because we used them so much) and cause problems with the brake lights and subsequenlty, the shifter interlock. More than once I had to rescue an unknowing Patrolman who had been on an extended traffic post with all the lights on, that couldn't "get the car out of park." I'd pull up, go through the whole 'put the ignition switch in the OFF position, move the shifter to NEUTRAL, then restart the car' routine to move the car. Invariably, the hazard switch would be red hot, and a replacement cured the problem. The hazard switch sometimes would give warning that it was about to fail as it would become intermittent in turning the flashers both on and off, and it would be hot to the touch when you would fiddle with it trying to get it to work. Just a suggestion. I'm no expert, I'm old school and put out to pasture, but I remember some things.

[ImpalaSlayer]

if no power to the switch and fuse is good sounds like wire has chaffing somewere and if the case it can be a pain to find were its causing the lose,dont think it would be cause a bad ground somewere

lets hope thats not it


I had a power gremlin once also. Turned out to be the power wire in the driver side sun visor twisted and frayed causing a short. Thanks to Carfixer for that helpful hint. Apparently a few 04s had that problem.

i doubt thats it but i guess its worth a look, cant hurt


See if you have power to the contact for the fuse, if good replace that fuse.

didnt check that end, will do so tomorrow


check fuses with a test light. a tiny strand of wire can carry 12 volts but will not be able to support any amperage. a test light will add an additional load and tell you if the fuse is actually good or not.

This may not be your issue but its a good habit to get into.

you didn't mention that you checked fuse 22 at the CJB. that is hot at all times and directly feeds the multifunction switch and brake switch.

ill give that a shot and check out fuse 22 as well


That does seem to be the only fuse that has all the described issues in common, but it also supplies power to the ABS module and the PCM, for what exact functions I don't know, but I would think there would be other symptoms... :dunno:


Since this seems to be falling into the category of "gremlin", I am going to throw this out based on experience. On the P71's, more than once the hazard flasher switch on the top of the steering column would act up (probably because we used them so much) and cause problems with the brake lights and subsequenlty, the shifter interlock. More than once I had to rescue an unknowing Patrolman who had been on an extended traffic post with all the lights on, that couldn't "get the car out of park." I'd pull up, go through the whole 'put the ignition switch in the OFF position, move the shifter to NEUTRAL, then restart the car' routine to move the car. Invariably, the hazard switch would be red hot, and a replacement cured the problem. The hazard switch sometimes would give warning that it was about to fail as it would become intermittent in turning the flashers both on and off, and it would be hot to the touch when you would fiddle with it trying to get it to work. Just a suggestion. I'm no expert, Im old school and put out to pasture, but I remember some things.

hmm wouldnt surprise me as this all happened basically the same time.

is there anyway to test a MFS?

[BODYMAN]

If the wires was chaffing you'd be blowing the fuse.... no?

Most the time I'D say yes but like Defyant describ wire twisted and frayed chaffing maybe not a good word for it. But yes agree most time you eat the fuse. I for one hate wiring problems they can become very time consuming

[Spectragod]

IIRC, the brake light circuit goes through the turn signal switch assembly. I would have to look it up to be certain, but that seems to pop in my head.

Does the car have an alarm or autostart? Did it ever have either?

Do the hazards work?
Do the park lights work?
Reverse lights work?

Or...... what else does not work?

[ImpalaSlayer]

IIRC, the brake light circuit goes through the turn signal switch assembly. I would have to look it up to be certain, but that seems to pop in my head.

Does the car have an alarm or autostart? Did it ever have either?

Do the hazards work?
Do the park lights work?
Reverse lights work?

Or...... what else does not work?

hazards do not work as stated in first post
i have to check for sure the other lights work
rev lights def worked, checked them today

[fastblackmerc]

Most the time I'D say yes but like Defyant describ wire twisted and frayed chaffing maybe not a good word for it. But yes agree most time you eat the fuse. I for one hate wiring problems they can become very time consuming

I used to be the "squeak, rattles, water leaks & electrical" man at the 2 dealerships I worked at. Electrical problems aren't bad to troubleshoot if you have access to the wiring schematics and use some common sense.

[babbage]

Sounds like a bad BOO switch (brake on off switch) when this fails a symptom is not being able to get out of park. The shift interlock works on a vacuum line solonid.

[Got_1]

Sounds like a bad BOO switch (brake on off switch) when this fails a symptom is not being able to get out of park. The shift interlock works on a vacuum line solonid.

he doesn't have power at the switch

[ImpalaSlayer]

ok so who ever mentioned fuse 22 is on to something heres what i did

i pulled fuse 22 and sure enough it was blown. popped a spare in and something started clicking, i hit the flasher button and it was on, when i turned it off the clicking stoped, so it must have been the flasher relay clicking.

even though the relay was clicking the lights were not working.

i shut the hazards off and tried the turn signals, they worked for a brief period of time untill the fuse blew again. in the midst of all that i tried the brakes and they still didnt work.

i pulled fuse 22 out again and it was blown, visualy and on the meter. it also took with it fuse 12 IIRC.

any idea?

[BODYMAN]

I used to be the "squeak, rattles, water leaks & electrical" man at the 2 dealerships I worked at. Electrical problems aren't bad to troubleshoot if you have access to the wiring schematics and use some common sense.

Yea youre right however I never liked doing wiring repairs and my attitude towards it made it a pita for me. Whenever I fixed a hard hit in the shop I always just passed the wiring repairs to mech in service dept, couldnt make any $ on it being flate rate;)