I have a 2001 Grand Caravan that was passed on to me about a year ago. Last week the left turn signals (front, back, and dash) stopped working. I had some friends look at it and they checked the bulbs and swapped the right and left sockets to rule all that out. We have even tried removing the battery and removing the IOD fuse for a while. Nothing has worked.

Any ideas on where to proceed next?
Thanks.

 

Do they work when the hazard lights are on?

 

No, the left turn signals still do not work when the hazards are on. The right side works just fine though.

 

Hmm. Two inputs from separate sources (turn sig switch, hazards switch) to the same box leads me to think the box is the culprit. That box being the Body Control Module (BCM). I would inspect connections and wiring before forking over the bucks for that pricey gem. BCM is bolted to the firewall above and left of the brake pedal. Try disconnecting the negative battery cable for 5 minutes. Want the wire diagram? Send me a PM and include an email address to send it to.

 

Had a coworker compare the right working side to the left nonworking side and noticed that the working side connector at the bulb (with four pins) he measured 3 grounds and 1 positive signal which is the flashing circuit. The nonworking side has all 4 pins measuring as grounds. He determined that there is negative voltage where there should be positive switching voltage.
He also cleaned up all connections and disconnected the negative battery and there was no change.
So are we right to assume that either the BCM is faulty or something else is shorted to ground?

 

That sounds expensive.

 

Pin #1 is the input to the turn signal at both the left and right rear light assemblies. Logic says if one is reading different from the other then yes the BCM is the likely culprit. Unfortunately, that's all I can say on it because I've never troubleshot your particular problem. All I'm going by is electronics experience and a wire diagram. To CYA you could disconnect the BCM then check continuity to ground at pin #1 at the light connector. Should read completely open - infinite resistance. That proves the signal wire isn't shorted to ground. You could also go directly to the output at connector C2 at the BCM and measure the output there just as you did at the light assemblies. That would be pin #2 for the left side rear and pin #4 for the right rear. Front lights are pin #3 for the right front and pin #1 for the left.

BTW - Have a trailer light harness installed? Disconnect it. It could be shorted and loading the system.