1999 Volvo s70 Possible MAF sensor issues

dcmatos · Post by **dcmatos** » 18 Sep 2015, 13:00

I had my MAF sensor replaced about 5 months ago because it was reading too rich and would not pass an inspection. It worked fine afterwards. I changed out my battery a week ago because the battery went dead after sitting for 4 months without running. I thought it was the fuel pump but a few codes came up when it was diagnosed at Autozone:

p0440
p0171
p0174

It may be possible that my MAF sensor is faulty, but I think there is a strong possibility that my 02 sensor is bad. I'm going to try to clean my MAF sensor first before jumping to the o2 sensor, since it is reading lean and it is cheap. I need a little advice/help if possible.

JRev · Post by **JRev** » 18 Sep 2015, 13:05

Did you replace with a Volvo genuine/Bosch? I only ask because from my experience if you use aftermarket then they will fail again.

Post by **abscate** » 18 Sep 2015, 13:12

That P0400 code is an EGR problem.

A vacuum leak (either in EGR or other hose) will cause all those symptoms and code. Leave the MAF alone and find that leak first

Post by **RussB** » 18 Sep 2015, 13:32

Yes, vacuum leak. Leave the good parts alone and look closely at all vacuum and turbo lines and hoses

dcmatos · Post by **dcmatos** » 18 Sep 2015, 13:34

JRev wrote:Did you replace with a Volvo genuine/Bosch? I only ask because from my experience if you use aftermarket then they will fail again.

I replaced it with a Cardone remanufactured MAF.

dcmatos · Post by **dcmatos** » 18 Sep 2015, 13:39

abscate wrote:That P0400 code is an EGR problem.

A vacuum leak (either in EGR or other hose) will cause all those symptoms and code. Leave the MAF alone and find that leak first

Sorry I meant to put p0440 instead of p0400

dcmatos · Post by **dcmatos** » 18 Sep 2015, 13:40

RussB wrote:Yes, vacuum leak. Leave the good parts alone and look closely at all vacuum and turbo lines and hoses

I'm sorry I mean to put in p0440 as the code not p400.

Post by **abscate** » 18 Sep 2015, 14:07

Thats an EVAP code - and...it will still give you a vacuum leak!!

dcmatos · Post by **dcmatos** » 18 Sep 2015, 14:18

abscate wrote:Thats an EVAP code - and...it will still give you a vacuum leak!!

Ha!

What's a good way to find the faulty hose? Just start up the car and take a look?

Post by **abscate** » 18 Sep 2015, 18:04

Careful VAT ( visual, audible, tactile) inspection.

A smoke tester is the definitive way to find it.

Your EVAP stuff is in front of the right rear wheel, btw. Don't let the 1998 location fool you.