I purchased a 2004 G35 sedan approximately 6 months ago with 120,000 miles on it. No problems until yesterday (outside of the CD player being jammed and the intermittent radio problems that are so common with this model).

Approximately 15 minutes after leaving the car wash I noticed that my car would not beep when I locked it with the remote. The doors would lock but the car wouldn't honk. I thought it was weird and I went into work.

After leaving work at the end of the day I noticed that my check engine light was on. I pulled into my garage and noticed my headlamps were on (even though I had them off). I turned the car off and back on and noticed the headlamps were still lit. I drove to Autozone and received the following codes from the CEL.

U1001
U1000
P0327
P1124
P1612

It appears that it could be a problem in the wiring harness, ECU, or grounding. I believe the knock sensor error can be related to the harness wiring... I am taking the vehicle to the dealer to have it diagnosed.

In the meantime, the headlight operation has returned to normal, and the car now beeps when it locks. There has been no difference in driving/idling/interior electronic performance throughout this entire situation. Should I consider resetting the ECU to see if the problem fixed itself? Or would following through with the dealership appointment be better?

Thanks in advance for any input.

 

Dealer Called:

Stated that they cleared the code and everything seemed normal on their drive. When they parked it and locked it the horn on the car started going crazy, and the codes reappeared. They cleared codes again and ran it and it ran fine. Upon locking it the horn went crazy and the codes reappeared.

Upon further inspection they discovered that the drain near the battery bay was clogged with dead leaves. They suspect that water could have gotten into or onto the IPDM, and that this could cause these symptoms. They also mentioned something could have gotten corroded. They are going to look into it further to the tune of 2 hours of labor...Looking at $350 after they tell me exactly what needs to be replaced...Bend over!

I will update when more information becomes available.

 

Total cost out the door is $1300 for IPDM replacement. Corroded due to water. Says harness shows corrosion but is salvagable. I'm not sure I would have been able to diagnose without them, but highly doubt I couldn't find an OEM IPDM for less than $750.

 

Lucked out and reviewed my insurance policy and it covered "water" damage. And fortunately it was covered. So all in all about $250 out of pocket, $100 deductible + battery and a few other small things. Plus I took a free diet coke when I picked it up today. So be sure to review your insurance policies if you think you have failure due to corrosion of any essential electrical component.