I own a G37x with 180,000 miles on it. This might be a bit long, so buckle up.

A couple of months ago, while I was driving, the car suddenly went into limp mode and then died. I had it towed to a shop, and they diagnosed a failed alternator—which made sense. I spent $700 to get it fixed.

Fast forward a few weeks: the car was running fine when I suddenly got a low oil pressure code and a VVT Solenoid Bank A code. I was worried it might be the gallery gaskets. Around the same time, I brought the car in to get new tires mounted and asked the shop to check the codes. When I picked it up, they said there were no codes and everything looked fine. I was confused, but since the car drove well, I didn’t worry too much.

However, about once a week, I’d notice the battery and brake lights flash for a split second—barely noticeable and very rare.

Then, this past weekend, I was driving on the highway when the battery and brake lights came on and stayed on. I assumed the car was about to die, so I pulled over and turned it off. It wouldn’t start back up. After waiting about 10 minutes and wiggling the battery terminals, it started again. I drove maybe two seconds before it went into limp mode and threw a check engine light.

I called a tow and scanned the codes. It showed a MAP sensor code and a lean fuel mixture code. I had it towed back to the shop. They replaced the MAP sensor, but I wasn’t convinced that was the root problem.

I got the car back and drove it for two days. Then the same symptoms came back, car went into limp mode so I pulled over. battery and brake lights, dashboard lights going crazy, rough idling, and even the windows wouldn’t roll up unless the engine was off. I left it overnight, and the next morning it started fine. I managed to drive it home, though the battery and brake lights stayed on.

I replaced the battery, but the issues persisted. At this point, I suspect it might be a bad BCM (Body Control Module), although I’m not seeing many of the usual signs of BCM failure. One thing I did notice is that the floorboard is wet, but the BCM itself doesn’t look corroded.

I’m really not sure what to do next. If it does turn out to be the BCM, I’m not sure it’s worth replacing it given the car’s value. Has anyone experienced something similar or have any ideas on what the issue might be?

 

Keep in mind that there are more electrics under there than just the BCM. The ECU is in that neighborhood as well as other modules and the related wiring. There have been cases where the ECU got water damaged while the BCM was totally fine.

I would check that the ECU is dry and not corroded. Also, make sure the wiring is in good condition and pay special attention to the various grounding locations under the dash area.

As far as repair costs vs. value- that is a equation only you can solve.