Hello all. Got my G63 in June. Only have 3200 miles on it. Back in September, I drove through heavy heavy rain in the highway. In the middle of the drive, bunch of service lights came on. ABS, Differential, Engine light on. When I got home, after several days, no lights were on, but the engine light did eventually come back on. I took it to the dealer and they check the electrical system. All good. They reset the codes, test drove it and lights came back on.

The last thing they did per the report replace the differential lock of the rear axle. After that, no issues.

Jump to yesterday, I go to an automatic touchless car wash. Only the front part went it the wash. And the lights came back on. The garage door for the car wash did not go all the way up, so I back up and left. Took it home and started it up today. Only engine light remain. Going to take it to the dealer in 2 weeks. Any idea what is causing this? Looks like a water issue? Water seal issue? So I can point them in that direction and I don't have to ever deal with this again.

I haven't driven the vehicle in heavy rain since September. Light rain yes and no issues. First time in a car wash. I've washed it at home with power washer, no issues.

 

This is a known weak spot. Water's getting into the rear differential control module. Its location makes it vulnerable. The seal on the module housing or its connectors is likely the culprit. Tell the dealer to inspect the seal and connectors at the rear diff lock module specifically for water intrusion. That should get them looking in the right place.

 

Thank you Alexie. Is there a permanent fix for this on their bulletins or it's going to keep happening even after a fix? Which the module was already replaced once.

The lights went away and the engine light has gone away and I've driven it for 200 miles. So I might cancel the appointment.

 

If the module was already replaced once and the lights cleared themselves, you likely have a loose connection or a wiring harness issue, not a faulty part. A permanent fix requires a proper diagnostic scan to find the exact fault code that triggered it, even though the light is now off. The problem will almost certainly come back if it's a wiring gremlin. I'd keep the appointment for the scan. If you cancel and it returns, you're back to square one.

 

As an aside, the dealer should be helping you. Not you helping the dealer because they suck that bad.

 

Anyone know of a bulletin that actually fixes this issue?

They fixed this last time. Replaced the wires which they saw was starting to corrode from water getting in.

2 weeks later, I pay for a hand car wash not even automatic and the engine light comes on again. Went away the next time I drove it. I drove it in the rain a couple days ago and the engine light came on and then the other lights (rear differential, etc.) comes on again. Getting really annoying now.