Hey everyone,

I couldn't find an exactly-similar problem to mine on the forums so I'm creating a new thread for this issue I've been having with my '01 S40, 52k miles. I recently did some fluid changes (power steering, ATF, brake fluid flush + change), but being the idiot that I am, I had spilled a little brake fluid onto the wiring/hoses directly beneath the master cylinder -- I immediately washed it off with water after spilling. It ran fine for a few days after.

However, I recently turned the car on in the morning and was met with erratic idling, shaking at low RPMs, and MIL with P0102, P0172, P0131, and P0301-4 codes. I didn't drive it after that and a few more days later (today) it flat out stalls on me when I turn it on. I thought it may be the MAF that's dirty at first, so I cleaned it with CRC cleaner and while I was at it I changed the dirty air filter, but no luck, same problems. I'm totally lost, what could be the issue? Could the brake fluid even eat through any hoses or wiring insulation? I inspected the hoses and clamps for any vacuum leaks, and I don't see anything.

 

Check that you didn't get some on the O2 sensor (your engine is different from mine, but I'm thinking that the upper "pre-cat" O2 sensor is probably pretty close to your brake fluid reservoir).

That could explain at least three of the codes. Electronics really don't like being doused in petrochemicals OR water. Some of those circuits are very low-current, so even a little conductivity from dirty / contaminated water on the connectors could be a problem - or worse, if there's some sort of ECU module in the area I'd have to wonder if it survived the double-dousing.

 

I'd be more suspicious of the MAF sensor than the O2 sensor. The codes are saying the front O2 sensor is detecting a rich condition, you have resulting misfires and the 102 is a signal issue from the MAF. I don't think the wiring to the front sensor is at risk from a spill (it runs from the firewall to the downpipe so you can inspect that wire for any damage. Then you can inspect the wiring going into the MAF but considering you've already tried to clean it, it could just be that the MAF gave up the ghost (If in the odd possibility that a vaccuum line sucked in some brake fluid into the intake, that could certainly damage a MAF but that seems very remote to me given your car didn't have any signs of an air leak).

 

Well, I didn't think it could get worse, but it did! Tried to backprobe the MAF wiring today to see if the voltage is correct, and when I turned the car on it stalled out and threw P0700 and P0705 codes for the transmission. Considering scrapping the car at this point.

 

the P0705 is pointing at your PNP switch. Not uncommon for them to build up corrosion on the contacts so try doing a shifter row to see if that clears it up. Back to your original concern about the brake fluid spill, seems you may need to start inspecting and opening the electrical connectors in the spill area and clean with electronics cleaner or similar to see if that helps. It may be you have a wiring issue or you need to replace the MAF and possibly the PNP.

 

Update: the issue was a snapped hose from the ICV to the intercooler! such a small part causing so much trouble and the 0705 was indeed the PNP switch. Thanks all for the help