2006 V70 2.4D, 325K KM/200K miles recurring fault: ECM-135F Mass air flow (MAF) sensor - Signal too low Topic is solved

[jvl]

Hi all,

First of all, I would like to wish you fellow Volvo enthusiasts all of the best for 2022!
Your thoughts on a recurring fault would be highly appreciated.

I bought a V70 2.4D this spring and it's currently at ~325K kilometers / ~200K miles. I've driven it for about 20K problem-free but now it keeps warning me: "Engine service required'. A readout with VIDA presents a fault in the ECM: ECM-135F Mass air flow (MAF) sensor - Signal too low. Other than this, there's a fault about 'incorrect checksum', this fault was already present when I bought the car and is probably due to the fact that the PO has had it chiptuned.

What I've done so far in an attempt to solve the problem:
- changed out the front vacuum engine mount that was leaking terribly, replaced with new mount
- changed out MAF sensor for identical used one from salvage car with about 150K KM / 90k miles, cleaned the connector.
- cleaned out the EGR, and found it to be relatively clean. Cleaned it anyway as I had taken it out already.
- renewed fuel & air filter
- cleaned the MAP sensor and connector
- reconnected the swirl valve control arm. This was already loose when I bought the car and hadn't given me troubles before, probably because the swirl valve has been disabled in the software with the chiptune (?).
- used DPF / diesel cleaner additive in the fuel 2 times. This did improve a rough start that is probably caused by leaky injectors, but doesn't seem to help with the issue above.
- checked the MAF and MAP sensors as per VIDA procedure. VIDA tells you to 'compare the temperature readings' for MAP and MAF and these temperatures are about the same. The only thing I find weird is that when I turn off the ignition, the MAF temperature drops down to -75 celcius / -103 fahrenheit. Is this normal because there is no air flow to 'cool down' the wire in the MAF sensor when the engine is off? When the engine is running, the values are about the same.

When I reset the code, it sometimes comes back on the first drive after the reset, and sometimes after a few drives. When it does, the CEL always seems to activate when the engine is just about to get to operating temperature (just before the temp needle hits the middle).

I'm thinking that it might either be a faulty MAP sensor or a leaky vacuum engine mount (I haven't replaced the rear mount yet).
Knowing that diesels are getting less and less popular and that i'll probably be the last owner, my aim is to only replace those parts necessary. Any tips on where to look before I start changing out many parts would be highly appreciated!

Thanks in advance as always,

Joost

[jvl]

Quick update:
- the check engine light sometimes dissapears, aaaaaaaaaaaaand then it's back again on the next drive. Opposed to my earlier post: it sometimes comes on when the car is already warm.
- I'm starting to think I might have a leaky air or vacuum hose and/or cracked intercooler, any experiences on easily doing a pressure test? I do have basic tools + compressor + mid rise lift so getting under the car is no problem.
Any thoughts?

Thanks!

Joost

[jvl]

Hi all,

As I had just a minor lack of power, I just kept driving the car up untill it's annual inspection. The CEL would occasionaly turn on and off. When on, I would experience lack of power due to it going into reduced torque mode. Upon inspection, I asked the mechanic to check it over and he found a loose pressure hose at the underside/backside of the turbo, the flexible part that connects the turbo to the pressure pipe that runs under the oil pan. After fixing that, all seems to be well again! The car runs great, pulls like a train and no CEL anymore.

Hope this info helps others in the future.

Joost

[jonesg]

a smoke test might have found that leak for you.