Did I toast the BCM?

Helping a friend- 06 Chrysler Pacifica. Left headlight out. No other evident symptoms. He replaced the lamp twice to no avail.

With lamp unplugged I put jumpers to battery and headlamp is good. With test light I find there is power but not ground. I can see where the harness bundle goes to frame ground so I remove bolt, clean terminals, refasten.

Tuning on key dash lights up like xmas tree, right headlamp blinking, gauges bouncing, and nothing works except power seat.

I'm wondering if I inadvertently sent 12v up the ground path with test light could I have broken something. Everything except headlamp worked before I touched it. Now nothing works. Quite embarrassing really.

Any or all advice appreciated. I need to make it right. And hoping I can do it personally. I did remove negative batt cable overnight hoping for a drain and reset. Also cycled key on and off for 15 sec. No luck.

Thank you.

Rusty Wrench wrote:

I'm wondering if I inadvertently sent 12v up the ground path with test light could I have broken something.

To be clear, you were using an incandescent test light, connected to B+, touching one of the headlight pins with the headlight disconnected, correct? And the test light did not illuminate? Do you recall the wire colors of the pins you were testing?

Strange things happen all the time. :silly: But I doubt you cooked anything at this point. We need more information. For reference, this is the left front headlight wiring:



Do you recall which ground you removed and cleaned? Here's a picture for reference:



We're specifically concerned with G103, as it not only grounds the left front headlamp, but also the Integrated Power Module:



It's entirely possible that the G103 eyelet or wires close by already had a problem (left front headlight inop), and you just exposed it by removing and reinstalling the ground. :silly:

If the left front headlight connector is still accessible, I'd recheck for a good ground at pin 4 black/light green. If there's still no ground, then there's still a problem. Revisit G103, voltage drop testing as you go. Check the bolt, the eyelet and the wires within 6" of the eyelet if possible.

Hi Tyler- I'm very appreciative of timely and in-depth response.

I'm using digital test light. Has led volt display; got a little circuit board in it. Scope on a rope thing.

With headlamp disconnected- put alligator clamp on B- and probe to one of two harness socket. The test lamp read 12v. And I said ok, we have power.

Then alligator on B+ and probe to other headlamp socket (presumably ground) and test light dark. I said ok, we don't have ground.

But checking it a couple times in that process I believe I also probed both sockets with both +12 and -12.

I don't recall wire colors but think I cleaned G104. I understand what you're saying. Likely won't re-visit the problem for a day or so. I will re-check for grounds at headlight pin and 103, inspecting carefully. Had forgotten about checking voltage drop :oops:

Thanks again, especially with the diagrams and have a safe and Happy New Year. I will follow up soon.

Rusty Wrench wrote:

I'm using digital test light. Has led volt display; got a little circuit board in it. Scope on a rope thing.

With headlamp disconnected- put alligator clamp on B- and probe to one of two harness socket. The test lamp read 12v. And I said ok, we have power.

Then alligator on B+ and probe to other headlamp socket (presumably ground) and test light dark. I said ok, we don't have ground.

But checking it a couple times in that process I believe I also probed both sockets with both +12 and -12.

Gotcha, thanks for the clarification. Digital test lights are absolutely harmless, IMO, especially on high current circuits like this headlight. If you did cook something, it wasn't from the use of the test light.

I don't recall wire colors but think I cleaned G104. I understand what you're saying. Likely won't re-visit the problem for a day or so. I will re-check for grounds at headlight pin and 103, inspecting carefully. Had forgotten about checking voltage drop :oops:

No worries. Happy New Year! Let us know what you find.

G103 was the gremlin
Illustration was invaluable

Zero voltage drop. The eyelet has 2 crimps; the strain relief crimp was mostly intact but the wires at the contact crimp were eroded away. Not so easy to see. Had to remove the battery box for easier access to repair.

New ring terminal. Everything works. Friend is ecstatic and I'm redeemed.

Thanks Much!!!
Don

Rusty Wrench wrote:

G103 was the gremlin
Illustration was invaluable

Zero voltage drop. The eyelet has 2 crimps; the strain relief crimp was mostly intact but the wires at the contact crimp were eroded away. Not so easy to see. Had to remove the battery box for easier access to repair.

New ring terminal. Everything works. Friend is ecstatic and I'm redeemed.

Thanks Much!!!
Don

Ayyyyyyy. Great to hear, Don! Both headlights are working now, too?

Not all OE's are as good as Chrysler about having illustrations like that, but they're nice when available.

Both headlights are working now, too?

Funny you should ask... and I think my memory is correct.
The original (low beam, outer lamp) lamp problem repaired and functional. Black/Lt Green headlamp ground (and 4 others) are solid now.

But... after repair, bright beam inner lamp has ground but no power. Did before. Obviously disturbed something.

However, my friend has two working headlights and he knows he dodged a bullet by finding a bit of weakness in the driveway rather total failure on the road. I wanted to trace the power loss but he'd had enough.

We're still good friends:)