I have a 2000 GMC Jimmy that the turn signals and flashers will not work when it is cold. Once I get rolling and it warms up a little the turn signals will work normal.. If it is not cold the turn signals will work normal all the time. I did replace the relay behind the glove box door but that did not correct the problem.
Could this be a BCM issue? I am open for suggestions.

 

1) When this happens are all 4 turn lamps inoperative?

2) When this happens does the park light function work at all 4 lamps?

3) When this happens does the hazard light function work?

4) Have you replaced the park relay and the flasher?

5) Does it matter if the park lights are on or off?

Check the following fuses for corrosion:

Turn fuse 20A IPFB
Hazard LP fuse 20A UHFB
Park LP Fuse 20A UHFB

The BCM is involved but only for part of the modes, the MF switch is involved in every mode.


George

 

1. All 4 Turn signals do not work and there is not dash indication.
2.Parking light works perfect at all 4 corners.
3. The hazard light does not work.
4. I only know of one flasher in my Jimmy and it is behind the glove box door. I changed that relay.
5 Does not matter if the parking lights are on or off.
6. All fuses are good.
It only seems to not work in cold weather. Once I start driving without any action by me the turn signals at some point will start working normal. They continue working normal if I make a stop somewhere and get back on the road.

 

There are two different relay like components involved in this function:

Turn Signal Lamp Flasher - behind right side of dash

Park Lamp Relay - Body relay block behind the left side of dash

Which one did you replace?


George

 

Sorry, I see now that you said you changed the flasher behind the glove box. If all your fuses are good and not corroded and the new flasher is known good then this is most likely a problem with your multifunction switch. To verify check the following when the turn signals are malfunctioning:

With the hazards on probe the gray wire going into the flasher behind the glove box and see if you have 12v

With the hazards off probe the light blue wire going into the flasher and look for 12V

In both modes look for flashing 12V on the purple wire

12V for the flasher is provided by the MF switch and then flasher output is directed to the correct lamps with the MF switch. Because of this the MF switch can fail in two ways. The BCM is involved but only to increase turn signal bulbs with no parking lights on so if the BCM was hosed it would not prevent all flashers.


George

 

What is strange is that everything works normal most of the time. It seems the only time the turn signals and flashers do not work is in the morning when it is cold outside. Today I pulled the fuses and made sure all contacts were clean. I started the car in the car port this morning and had the flasher turned on (not working) after about 15 to 20 min the flasher was flashing and all turn signals worked properly, Earlier this year I did replace the MF Switch because the turn signals quite working. I have had no issues with any of the functions up until a couple of weeks ago.

 

Intermittent problems can be a "challenge" (insert %$#*&&* here). You need to narrow down where this coming from. Right now I think your best bet is to probe those three flasher wires when you have the problem in the morning. That will eliminate a section of the circuitry. The good news I guess is that its winter and hence, cold outside. ;-)



George

 

You are correct, intermittent faults are the hardest to isolate and correct. I will check the voltages at the flasher when I get the chance. I suspect that when there is a failure there will not be any voltage present at the flasher.. You have to start somewhere. I do not think I have faulty MF Switch as there different contacts within the switch for the turn signals and the flasher. I will either get to the bottom of it or I will end up taking it to the dealer. I was hoping it was a faulty flasher relay. That would have been the easy and cheap fix.

 

Here is another thought if some electrical probing does not nail it:

Have a blow dryer ready and hit all of the relevant components to see if its heat related and where. Fuse panels. relays, flasher, MF switch, etc.

George

 

The hair dryer is a good idea. I do have a set of factory service manuals and I have been reviewing the wiring diagrams and it seems that I should have power from the IP Turn Fuse to the closed contacts for the M/F HZD switch right to the flasher (HZD to Flasher Light Blu wire). In flasher mode straight from the UH HAZD fuse through the Contacts in M/F Flasher HZD Switch to the flasher (Gray Wire). My plan right now is to remove the flasher and check for power to ground at the flasher. On both the primary and Secondary power (HZD Off Cavity A1 to B2) & (HZD On Cavity B1 to B2) If I have power present than I will double check the relay, and scratch my head for other possibilities.