d5 (s80 2002) "engine service required" solved

[matthewb]

Posting this in case anyone else has similar issue.
Background.
My wife was driving our s80 to work when it accelerated erratically under throttle and "engine service required" info mesage came on and it went into limp mode.
She pulled over and 15 minutes later i arrived, swapped cars and i drove it home.... all working completely normaly.
A few days later it went into permanent limp mode ( just before christmas)and has been like that since.Drives ffine, just no turbo and rev limited.

I had the codes read at volvo and they returned the following
ecm-1300 mass airflow sensor signal low
ecm-4405 egr valve flow troo low
ecm-6800 vnt regulator signal too low

Faults cleared and then immediately back .

Truro Volvo thought the egr or the turbo VNT the most likely culprit.

I stripped the egr out and cleaned it. It wasnt all that dirty, a bit of loose fine dust but not loads and it didnt seem sticky at all - no change,
I changed fuel filter ( it was due anyway)- no change

A friend has one of the elm327 bluetooth diagnostics with the (Torque pro) android app and interestingy this connected to my '02 volvo an flagged up the same codes as Truro Volvo main dealer had.... BUT it also showed NO info at all form the EGR in the live data... consequently i wondered if the EGR solenoid was duff. So i disconnected the EGR solenoid and turned the ignition, this time as well as the " engine service required messsage" i also got an "emissions service required" ( or similar i cant remember the exact wording). Plugged the solenoid back in and this message went away..so i assumed all was well with the EGR....
So next up was VNT. This required stripping out the turbo... which i didnt fancy so i thought i would have a look at the maf sensor instead.

The MAF on my D5 is part# 0280218088 and its a bosch with 5 wires.
After some google digging it looked ike it was meant to have a signal somewhere around 1 volt at idle fed back to the ecu. so after more digging and the purchase of a new multi meter i started measuring. Mine was feeding back 6.79 volts........... culprit found ( i hoped) i got on ebay and 3 miles away a breaker had a new maf for £20...... fit maf.. turned ignition to position 3 without starting...." engine service required" message popped up............ again........but then immediately dissapeared.. started her up and car is runnng fine now....
if you want to check your maf voltages then on my 2002 s80 d5 with the Bosch 0280218088 MAF fitted the pins to check are pins 3 (common) and 5 (signal). Pin 5 is the far left pin ( stood in front of car looking into engine bay) and pin 3 is the middle pin. I used a small pin/nail/tack pushed into the back of the plug so i could get a connection. At idle he voltage should be around 1volt and as the revs go up the voltage should increase up towards 4.5 Volts. Mine was 6.79Volts all the time.

In hindsight it seems obvious that this was an electrical fault because when clearing the codes the faults would immediately reappear if powering up the electrical system even BEFORE starting the engine.So a faulty sensor was feeding back faulty info to the ecu without the engine running.
Anyway.. all solved.if it reoccurs for any reason i will update... but fingers crossed and i hope this info is useful to someone else!

[cheshired5]

With Torque Pro, all you need to do is go to real-time information and bring up a dial showing MAF reading.
This will show instantly that you have a MAF response issue before you even lift the bonnet.
Faster and easier than taking voltage readings with a multimeter.