2001 V40 MAF Sensor code P0102 other cause?

Billbrink · Post by **Billbrink** » 06 Oct 2015, 04:45

I know this has been touched on in a few other threads; I've read them all and this is a little different. About 5 weeks ago I pulled in the garage, shut the engine off and the cooling fan continued to run for about 20 minutes. It had been a very hot day, but the temp gauge never rose above normal operating temp. When I started up the following morning the Check Engine light was on. I ignored it for the moment and after a couple days, the light switched back off. In the following days, also very hot, the engine would quit on me, always in gear when I was slowing down to make a turn, stop for a light, or even in stop and go traffic. In every case I was able to throw it into neutral and restart without any hesitation whatsoever and no repeat of the stalling for potentially hours of more driving. I had the code checked and it was P0102, so I got a can of proper MAF sensor cleaner and did a textbook job of cleaning the sensor and contacts (at the sensor end). I zeroed the code and it drove fine for about a day then the same thing happened.

The thing is, the code has cleared several times with normal driving and when it returns it is always followed by the cooling fan running after I shut the engine off. I experience no performance issues with the engine at speed; no hesitation, no roughness, nothing. When it stalls it's instantaneous, and usually still rolling so the first clue is brakes and steering get a little harder.

As for other details about the car: For the last couple years, it seems like when the engine is warming up, the turbo can be a little slow on the draw, and suddenly kick in at higher RPMs. It only has 102K on it, and the ac blower motor seems to have a mind of its own, and every single bushing has either been replaced, or needs to be, or both. Basically a typical '01.

This doesn't seem like a sensor failure to me. It's too intermittent and brief. Given the hot conditions here in Austin, I'm running the AC, which I suppose may open up a whole can of potential vacuum gremlins. I'll have a go at disconnecting the sensor while it's running to see what happens, but any suggestions on what else would cause this sort of thing would be appreciated. I think the strange tie-in with the cooling fan must mean something.

Post by **alschnertz** » 06 Oct 2015, 18:46

I know the cooling fan on my '01 S40 seems to have a mind of its own sometimes. It doesn't usually run for more than a couple of seconds after shut-down. But, there have been times when it runs constantly with the engine off and key in position II (run). Simply shutting the key off and then on usually kills the fan.

And a heater blower acting wacky is not unusual on an ECC equipped car from what I've researched. Not saying it's right, but it can be typical for an aging ECC board.

As for the MAF, all I can say is that when it failed our '95 854T, there were a couple of stalls before it gave up completely. I couldn't detect a pattern, but it was my daughter using the car at the time, and she's not quite as car-savy as her dad.
It took 2 "new" Bosch units before getting a good one. Buy from a reliable supplier who will take electrical parts back if you go that route. It worked for me (thanks FCP).

Billbrink · Post by **Billbrink** » 11 Oct 2015, 14:33

Update. Talked to a relative expert about issue and he agreed that it did not sound like it was actually the MAF sensor causing the problem. He suggested i clean the throttle body, so I did. It was surprisingly clean. With minimal crap accumulated on the throat or the butterfly; certainly not enough to cause any sticking or impairment of movement. Its overall cleanliness apparently indicates the PCV trap is not the culprit either.

This is getting weird. I have driven the cycle, had the engine light go off, then the next day the engine will suddenly quit. On one occasion, I was on a highway, directly in front of a massive dumptruck being hauled on a giant flatbed trailer, which took up almost 2 lanes. I'm going 60 mph and take my foot off the gas; suddenly the engine quits. I can't pull over with Optimus Prime rolling up behind me, so I slip the transmission into neutral and restart. The engine started quickly, but with a jolt, and on I went with no more trouble until the next day, when it quit on me in a parking lot, having only been driven about 150 yards. (again: in gear, rolling, with my foot off the gas pedal).

What are the odds that a static sensor with no moving parts would fail- only under certain conditions, but only once for every 25 times those conditions occur?

Post by **alschnertz** » 12 Oct 2015, 05:24

Don't know why I didn't think of this before, but what about the Throttle Position Sensor?

I had that go on the 854T as well. And thinking back, your symptoms are very similar to what I experienced. Even more so than the MAF issues that I had.

Billbrink · Post by **Billbrink** » 10 Dec 2015, 19:40

Resolution. Guess what. It WAS the MAF sensor. I picked up a cheap $40 one and swapped them out. All the weirdness stopped. How this had anything to do with the cooling system is beyond me.