Volvo Repair Questions? Ask a Mechanic for Answers ASAP
Hello and thanks for your question. My name is XXXXX XXXXX I will do all I can to help.
Let me first ask, do you know exactly which codes were stored?
i think it was P0101
that was it? just 1 code stored?
it showed up twice
one time there was a code about fuel rail
alright, fuel rail pressure sensor maybe?
meaning there is usually 2 codes both P0101 and sometimes there are 3 the other being the fuel rail code
when looking at the fuel pressure on the scan tool is looks good and doesn't drop when running or stopped
OK, This P0101 showed right back up after replacing the MAF though? and that was the only code stored at the last time you scanned it?
Alright, give me just a few minutes to look over a few things. thank you.
I'm digging here, sorry to keep you waiting going through all data now. You may wanna check back in 5 to 10 minutes here. I wanna give you the best answer I can.
I love the way they are real precise here in their possible causes.
that's what they have, I'm digging in the wiring diagram now, do you have a voltmeter
ohm meter and a volt meter?
alright, Here's a diagram of the MAF circuit, first thing to do is make sure the GREEN wire has battery voltage with Key ON.
give it a second to load.
ok right now there is a box with a broken page
check it now.
I see it when I click it.
The VIOLET/WHITE wire at the MAF should have 5 volts reference voltage with key on engine off, when measure between that wire and chasis ground.
And the GREEN wire should be battery voltage around 12 with key ON Engine Off.
ok i see it now
alright, MAF is at the top. you can blow it up with the + icon.
when you monitor the MAF signal with your scanner. does it change with engine RPM? have you tried getting in that data stream/?
yes it does
So we can conclude that the wire from the MAF to the ECM is good then, and if you got a P0101 with 2 different MAF sensors, then we can also just about be certain it isn't the MAF itself.
This sensor aftermarket ? or came from Volvo. (it would be a bosch sensor).
i didn't get it from volvo but it is a bosch
alright, going through what the causes of the fault code can be, I would verify correct voltage on GREEN and VIOLET/WHITE, and if they show 12 volts and 5 volts, I would smoke test the intake system, (sometimes these vacuum leaks on turbo's can be hard to find, that pipe that goes to the ETM under the intake has been known to melt from the inside out or crack and only leak under boost).
If that pipe looks good and the voltage checks out, The only thing that is left is the ECM software bungled up and you need to update to the latest version, or the ECM itself which I highly doubt is defective.
ok how do you do the smoke test
One thing I like to do, is get somebody inside to stall test the engine, (FULL BRAKE and 1/2 throttle in D) to get some boost pressure in the hoses, then you can hear and feel around them and see if anything is leaking pressure.
put the E brake on fully as well, and trust them. :)
Smoke test takes a machine, similar to a fog machine at a concert. it pressurizes the intake system. alot of shops have them now. you take the fresh air hose off the MAF sensor and use an adaptor to pressurize all of the vacuum and turbo hoses with smoke liquid. then you just look for the smoke.
best way to find vacuum leaks in my opinion. it takes a big leak on these to find it spraying carb cleaner around hoses and connections.
Has it ever been updated to Volvo's latest and greatest software that you can recall? I swear I think they build some glitches in after 5 years or something. lol.
yeah thats what i tried
Alright, that can "loosen" up the ECM a little so it doesn't look at everything so critical, expand the parameters a bit.
yeah it has 161,000 miles
ok i will check the voltages and for leaks. if everything looks ok i might have to bite the bullet and bring it to volvo
I don't believe you have a wiring issue if you can monitor the MAF and the signal changes. and I don't think 2 sensors are bad. So I would say that either a software upgrade or you have a vacuum leak somewhere . I seriously doubt the ECM has an issue, it's a possibility, but I would be 99% sure it hasn't failed with just 1 code stored. I believe a smoke test for vacuum leak or software update fixes it.
Yes, If you don't have an independent that can perform software downloads on volvo's then it will be a dealer only type operation. Some import independents have invested in VIDA system, but unless their Volvo specific they prob. don't do it.
ok thank you
Alright, thank you. have a good week.
thanks you too