Accelerator pedal (AP) fault codes
 

Hi all,

Happy Christmas fault code advice required!

My old man's 2009 V50 T5 (35k miles) has been gone into limp-home mode three times over a couple of months. I read the codes yesterday, a couple of weeks after after the second event, and got...

ECM-941D - AP sensor, analogue signal - Signal too low
ECM-9430 - AP sensor, analogue signal - Faulty signal
CEM-3F93 - AP sensor - Signal too low

Then last night it shut down again, and repeated ECM-941D and CEM-3F93.

The first two shut-downs were straight after a cold start. Yesterday's was on the move. Gut feeling...it's either the pedal sensor itself (I know these can give trouble), or a wiring issue.

I've heard good reports of people cleaning the tracks inside the pedal. Any views?

Your thoughts, please!

cheers

James

Hi James !

Firstly the 2 ECM codes are being caused by the CEM code so you can ignore those .
It may help if you know how it works :
The pedal sends out 2 signals , One is digital and goes direct to the ECM , the other is analogu a 0 - 5 volt signal varying with throttle position . This goes direct to the CEM and is converted in the CEM and sent on the network system to the ECU . This is like a plane where everything is duplicated .
So the ECU monitors these two signals and they must both give the same reading in the ECU .

This signal is only failing intermittantly so any fault tracing you do is going to show ok you are never going to be lucky enough to catch the sytem in the fail mode to fault trace it .

I would check the wiring plug on the pedal first . unplug it and with a thin terminal of similar size just press it into each socket in the plug one by one to make sure there is drag when you insert and pull it out . This will test that the terminal is in fact gripping the pins in the pedal socket ..
Get some volvo rapid rust loosener 1161658 and spray the socket and put it back .
next remove the CEM and do the same with the relavent plug which contains the pedal signal wire . Check all the CEM pins for corrosion especialy the big green one .

Hopefully this will do the trick although it may be some weeks before you know .
If it still happens you could run a new wire down from the pedal to the CEM .
Changing the pedal is the last thing before changing the CEM or ECM .. I have never found a pedal which is actualy faulty with this problem .
You do get it serviced properly and have the software updates i take it .. The CEM gets updated at every service so you need to know this has the latest software .

I hope that helps ,

Hi Nick,

Many thanks for your expert assistance, and for confirming my suspicion that this would not be as simple as a failed pedal. A couple of quick questions, if I may...

Is the rust loosener a contact cleaner? I don't have ready access to the Volvo stuff (see below), but I can probably find a substitute.
Where is the CEM located on these cars?

The car gets serviced as a local independent Volvo specialist, but they don't have access to VIDA, as far as I'm aware. The nearest dealer is a considerable drive away, sadly, although making a special trip for a software update won't be a problem. I remember you saying something similar about my V70's SAS error...which I must confess I have yet to get around to looking at!

In other news, I was hearing last night that the "other" local indy replaced a pair of track rod ends, then didn't check/adjust the tracking, which proved (weeks, and considerable tyre-wear, later) to be 20+ degrees out! That one left me open mouthed...

cheers

James

The Rapid rust loosener is slighty acidic so it actualy cleans the connectors of any corrosion , rather than just cleans grease off like brake cleaner or lubricates to prevent the air getting to the contact points .
It is brilliant on manifold studs and other stiff or rusy threads . I always keep a can in my box despite it being £6 a can . well worth it .

The CEM is under the glove box , the big white unit with the fuses in ,it has about 3 plugs on the underside , then it will hinge down after removing two thumb screws , then you can remove the other 5 or so plugs and remove the CEM from it's bracket , it kind of slots out .
Disconnect battery first then all you will loose is the time !

Thanks Nick - I'll have a play if the rain ever lets up!

cheers

James

yes indeed , bridge on the point of closing here and gales and lashing rain i havent been in my garage for a week !

That'll be a job for next year then?? :rolleyes:

:star-wars-smiley-01

Just a little update. I pulled the CEM shortly after Christmas (which was a fun job...!) and cleaned all the pins...and it has been good as gold ever since. Many thanks, Nick!

cheers

James

That's a good long test , If it does come back , replace the Analogue signal wire from pedal to CEM ...
Best wishes ..

Foggyjames, did this issue reoccur at all over the last year? I have the same fault and fiddled with the CEM and it went away for 2 months. What cleaner did you use? Thanks