S40 (New) Electrics : Help with possible ECU Fault and part numbers

[Mikey360]

Hi all, new to the forum, spent a long time reading though other topics and always found you guys very helpful.

I've got a 2010 Volvo S40 D5 manual, bought it knowing it had this fault.

Bit of back story, it's had the DPF and CAT gutted and then remapped (Not done whilst I've had it), it feels like it's in limp mode with no power and no boost. No messages on the dash and no fault codes other than 3A00 which I believe is common if anything has been remapped on the ECU.

It's been with my mechanic for about a month, he does some basic remap work too. He's tried putting a fresh map on the ecu to try and cure the lack of performance with no success. Tried swapping it out with a map from a 2009 V50 D5 auto that he remapped a couple of weeks ago as he removed the swirl flaps. This did manage to bring up some codes related to DPF pressure sensors etc, but it still ran exactly the same.

It's clearly had a replacement ECU at some point as there's some chalk writing on it saying "V70"

He's can't take it any further, he's suggesting trying a replacement ECU to see if that fixes it, However....

The ECU that's currently fitted is 307299826, VDASH is stating that the ECU part number is 31272463.

Has the incorrect ECU been previously fitted and that's why it's not happy, or do the part numbers not matter as long as it's for the same Volvo?

Planning on buying a second hand ECU and getting it cloned, but thought I'd ask here before wasting money on the wrong ECU.

Thanks in Advance!

[Mikey360]

Forgot to mention he's checked things like the turbo, intake leaks, MAP sensor etc

[pinballdave]

The part number returned by VDASH (and VIDA!) comes from the software loaded into the ECU, so will be the part number from the original ECU that has been cloned, and may not match the hardware that it has been cloned into.

Volvo has several different ECU part numbers for what is essentially the same circuit board in the same box. The difference is in the software inside the ECU, and in some cases components on the circuit board are added or removed depending on options. So in some cases it's possible to clone an ECU to one with a different part number. as long as it contains all of the optional components the original ECU uses.

Now I don't know if this is the case with your ECU, it may have been cloned into a different but compatible unit, or the replacement might have some subtle difference that is causing the fault.

Cars that have had ECU modifications to remove the DPF or EGR, often seem to end up with faults that do not trigger codes. So make it much harder to fault find.


Of course it could be something similar to my S40, which I bought with similar low power faults and a 'gutted' dpf, and eventually found a golf ball sized chunk of the DPF matrix wedged half way down the exhaust pipe blocking off the flow.

[Mikey360]

Originally Posted by pinballdave

The part number returned by VDASH (and VIDA!) comes from the software loaded into the ECU, so will be the part number from the original ECU that has been cloned, and may not match the hardware that it has been cloned into.

Volvo has several different ECU part numbers for what is essentially the same circuit board in the same box. The difference is in the software inside the ECU, and in some cases components on the circuit board are added or removed depending on options. So in some cases it's possible to clone an ECU to one with a different part number. as long as it contains all of the optional components the original ECU uses.

Now I don't know if this is the case with your ECU, it may have been cloned into a different but compatible unit, or the replacement might have some subtle difference that is causing the fault.

Cars that have had ECU modifications to remove the DPF or EGR, often seem to end up with faults that do not trigger codes. So make it much harder to fault find.


Of course it could be something similar to my S40, which I bought with similar low power faults and a 'gutted' dpf, and eventually found a golf ball sized chunk of the DPF matrix wedged half way down the exhaust pipe blocking off the flow.

Thanks for the reply, would be interesting to see if the different ECU numbers would cause the fault! Might order 2 replacements with both part numbers and get them both cloned.

Haven't had the exhaust off yet, it does rev quite freely when not under load so not sure if there could be a block in the exhaust.

[domhart10]

I think I would go back to the start on this, you should be running the ECU for your car. If its not then im not sure how they managed that and it would defenitly be causing an issue with the car.

If the ECU has been opened / tampered with then yes I would also expect further issues like water ingress etc which do play games down the road with your car.

Best bet is to find a second hand ECU that is for your car (Ebay should have some) brand new ECU's are incredilby expensive. There is a difference in ECUs between PFL and FL models.

Then I would get a reputable mapper to start a fresh from an OEM map to make sure your car is running right with a dyno print out so you know nothing funny is going on.

[Mikey360]

Originally Posted by domhart10

I think I would go back to the start on this, you should be running the ECU for your car. If its not then im not sure how they managed that and it would defenitly be causing an issue with the car.

If the ECU has been opened / tampered with then yes I would also expect further issues like water ingress etc which do play games down the road with your car.

Best bet is to find a second hand ECU that is for your car (Ebay should have some) brand new ECU's are incredilby expensive. There is a difference in ECUs between PFL and FL models.

Then I would get a reputable mapper to start a fresh from an OEM map to make sure your car is running right with a dyno print out so you know nothing funny is going on.

Yup fully agree, just ordered the original part number for the ECU, will get it cloned, fitted and see what happens, thank you!

[Mikey360]

Quick update for anyone following this, correct ECU cloned and fitted.....
No difference unfortunately.

Will try to get it properly remapped on the new ECU and see what happens!