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Discussion Starter · #1 ·
Hello,

Been troubleshooting for a week. My wife banged into the headlight/turn signal control knob and that is when things stopped working.

I have taken the steering column apart and visually inspected all the wires and harnesses and can't see anything damaged or disconnected. I actually got a replacement headlight control knob and that didn't fix it. I have checked and double checked all the fuses and bulbs and nothing appears blown. I have swapped some of the relays around that control headlights and ecm to see if that might be the problem and still not lights.

Any thoughts on anything else I can try short of taking it to my mechanic and probably spending hundreds of dollars?
 

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There are fairly detailed troubleshooting instructions for the lighting control system available in the Factory Service Manual. However, the entire system is a sort of hybrid digital/analog control scheme that uses the various switch positions in that knob as a kind of logic matrix, which then instructs a cpu to operate the various components. In other words it's not a simple, straight-forward switch & relay system. The troubleshooting instructions actually describe procedures about reading voltage pulse widths, timings, etc.

So short of anything obvious, a trained technician with the proper tools may be your only option.

One thing you might check are the other connections to the second combination switch on the steering column (wipers). Both of those switches are actually wired together and function as one device in the logic matrix, so there could be something you missed on that side.

Also, does the buzzer still come on when the lights are set to on when the engine is stopped? If not, then it is probably something in the control circuit that isn't communicating properly with the BCM (Body Control Module). If it still works then it's likely a fuse somewhere in the actual lighting power circuit.
 

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Discussion Starter · #3 ·
Thanks for suggestions. So I took it to my mechanic today. He told me it's the BCM but I should take it to the dealer because even if he replaces the BCM the dealer will need to reprogram it to get it to work with my keys.

Is this true? I've read that can cost upwards of $800 at the dealer but I have seen the part for sale for $160

http://www.automotix.net/usedautopa...046572f.html?gclid=CIWN9vaAqboCFYdQ7AodETYAHQ


Can I buy this and replace it myself or will I still need to pay the dealer for work?
 

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I don't know exactly what the BCM does in the starting circuit, but the description from the FSM reads as follows:

BCM sends a starter request signal to the CPU of the IPDM E/R
over the CAN communication lines.
So I suppose that could be correct.

However, how did the mechanic determine the BCM needs replacing in the first place? (just curious)
 

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Discussion Starter · #5 ·
I don't know exactly what the BCM does in the starting circuit, but the description from the FSM reads as follows:



So I suppose that could be correct.

However, how did the mechanic determine the BCM needs replacing in the first place? (just curious)
He said he checked everything with multimeter and ran diagnostic. He said he was able to send commands using his computer and turn the lights on so technically everything is working electrically. He also swapped the switches that lead to the BCM with two different known good switches from another Xterra.

After picking it up from the mechanic and talking in more depth I think he has a strong hunch but not 100% sure. I have an appointment with the dealer in two days and getting ready to bend over for them :crybaby:

But I need to get this fixed
 

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He said he checked everything with multimeter and ran diagnostic. He said he was able to send commands using his computer and turn the lights on so technically everything is working electrically. He also swapped the switches that lead to the BCM with two different known good switches from another Xterra.

After picking it up from the mechanic and talking in more depth I think he has a strong hunch but not 100% sure. I have an appointment with the dealer in two days and getting ready to bend over for them :crybaby:

But I need to get this fixed
Be sure to let us know what you find out. I'm very curious about this myself. :scratch:
 

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Discussion Starter · #9 ·
So the dealer said the problem was a short in the wiring harness in the steering wheel that the combination switch connects to. $600 to replace it.

The good news is they are going to replace my transmission and radiator for free based on some recall and that would have cost $7000 if I had to pay for it. So sometimes it pays to go to the dealer
 
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