Problems after flood

We have a 2000 Montana. It was recently involved in a flood.

The water was high enough to come into the passenger compartment, but didn't get into the crankcase, transmission or air filter housing. The car started fine after the flood, but would not rev above idle. I discovered that the exhaust system was full of water, and drilled a hole in the muffler. Water seeped out for about 1/2 hour, and I was able to drive the car home with no problem at all.

Since then, the car has been throwing code P0131, P0137 and P0401.

We are selling the car in a couple of weeks, but I don't want to sell it with the MIL on. What should I check first?

Those are codes for the O2 sensors before and after the cat....

It's possible the sensors were contaminated by the water in the exhaust.....or there is water in the harnesses to the sensors that is causing problems.....

The other is insufficient EGR flow, not sure if there is a blockage in the pipe to the EGR?

Thanks for the reply.

I was thinking that the O2 sensors were probably damaged by the water. The flood was a few weeks ago, so I doubt there is water in there now. The van has been driven a lot. My son drives it, and he works about 30 minutes away by highway, so it has had plenty of chances to warm up well.

Yeah, I'm not sure why the sudden EGR code either. I can't figure out how it might be related to the flood. It might be somehow related to the malfunctioning O2 sensors? This EGR doesn't work by vacuum, does it? I think it's electronic.

I guess I was hoping someone might see a relationship between the flood, O2 codes and EGR code.

Exactly how high did the water get on the outside of the car?

Exactly how high did the water get on the outside of the car?

About halfway up the plastic panel at the bottom of the doors.49692

OK, since you were trying to start the car, it's possible water went into the tube to the EGR....wither it affected the EGR, or may have carried crud into the upper plenum passage, I don't know....

A scan tool will be needed to check out the O2 sensors, and also to activate the EGR, by progressively opening it.......if it causes the vehicle to stumble, you know it is opening.....but if it still sets the code after resetting it, it could be a blockage in the upper plenum......

I think I'll take it to a mechanic with a good scan tool rather than gamble on replacing parts to no avail.

BTW, just to be clear, I didn't try to start it until the flood receded. This photo is from the very worst point of the flash flood, taken by one of my son's coworkers. He parks the van at this warehouse, then travels to his worksite. While he was gone, the flash flood took place and no one could move the van. It's actually sitting on a slight hill, which probably saved the engine.

About halfway up the plastic panel at the bottom of the doors.49692

Oooow, that doesn't look good at all. Looks like the water is right at carpet height. Was the interior swamped too?

Can't even imagine what a nightmare this would be to deal with.

Please let us know how this plays out.