850 Non-Turbo ECU/ECM Replacement

[ShahinS]

I don't get it .....what is the problem then

Your mechanic said that the car is running rich....

If your car is running rich(like he said)you would have a black smoke from the exhaust as a result of unburned fuel and that's a fact.

Sorry maybe I didn't explain it well enough. He was getting the MAF Code (I Don't know the code#) he put a new Bosch MAF on, and he was getting reading all over the place from the MAF it was fluctuating from 30 to 90 at idle, but the O2 sensor was was trying to accommodating it. When he swaped the ECM with a one at his shop he was getting constant reading from the MAF, so he concluded that the ECM is bad. But he was saying that the O2 sensor and the ECM was working together to solve the fluctuating issue, well in fact, there is no fluctuating problem, the MAF is working fine but ECM is not, he also cheked the MAF wire too to make sure the wire was good.

Conclusion from him: This is a bad ECM unit thinking that the MAF is going up and down all over the place, hence giving a bad MAF sensor code.

Menahile car is running fine thu, hope this makes sense...

[misha]

Like i said before....bad MAF will make rpm's go up & down following with black smoke or sooth from the exhaust,loss of power.Fuel consumption would be a double or triple higher than usual.

Bad (front)o2 sensor will also make the car running very rich=abnormal fuel consumption(and from my personal experience...those are the only symptoms of a bad o2 sensor).
If you don't have the symptomes from above,than both of those sensors are completelly fine.

[Matty Moo]

I have an ECU here that you can have for the price of shipping if you want to try that route. I imagine it would sit here for the next 20 years otherwise.

[ShahinS]

Like i said before....bad MAF will make rpm's go up & down following with black smoke or sooth from the exhaust,loss of power.Fuel consumption would be a double or triple higher than usual.

Bad (front)o2 sensor will also make the car running very rich=abnormal fuel consumption(and from my personal experience...those are the only symptoms of a bad o2 sensor).
If you don't have the symptomes from above,than both of those sensors are completelly fine.

misha,
First of all THANK YOU! You have been very helpful. Believe me that I have been scratching my head over this too, and I think I really should go to another Volvo shop and get 2nd opinion, so I'm going to go for a joyride tonight try to get the CEL come on again!... I am in such a time crunch here, but thankfully the car is driving fine for now. Thanks Again!

[ShahinS]

I have an ECU here that you can have for the price of shipping if you want to try that route. I imagine it would sit here for the next 20 years otherwise.

I just PMed you!... Thanks!

[misha]

...I think I really should go to another Volvo shop and get 2nd opinion...

I was about to say that to you but....it's very hard to find a decent mechanic who will not try to rip you off nowadays.Volvos are not complicated to work on,but mechanics(or should i better say electronics tehnicians) with a good experience with them are hard to find.

Good luck!

[ShahinS]

Drove the car almost 90 miles and the light didn't come on, I double checked my milease, I was getting 22mpg in city driving. So all was good, but I ordered a matching part number ECM/ECU (0 261 204 224 & P01270416 and FD.2 lettering on the right side) from Ebay and took it to my Mechanic, we replaced it, he reset the MAF reading and double check everything, and all was fine. So now I have done 50 miles with this new ECU and all is good, the car is running better overall, it has more acceleration and shifting is a bit smoother.

Question: How hot the ECU/ECM box should get, so there are AC lines going into it, but it is normal that the ECU be very hot to the touch?

[misha]

I don't want to evoke a bad luck,but you didn't neither had a code with your old ecu after reseting.You also had the same mileage,engine ran smoothly...etc....it's also the same with the replacement ecu.

So...everything was also ok with the old ecu.

My opinion is that your mechanic just trying to hide himself from being wrong in it's diagnose....it happens all the time.