D5 Limp Mode, No Codes, DPF Temp Sensor?
 

Hi all, I very rarely visit here any more as my 2012 XC60 D5 AWD has been super reliable over the past 4 years of ownership, mileage now 125k.

However an intermittent power loss issue has recently arisen. This has so far only happened twice during the last few days as follows... engine is just up to temp after approx 5 miles, under light throttle and gentle acceleration, it goes into limp mode - no EML. Stop and switch off briefly, restart and still in limp mode. Switch off for a few minutes and normal service is resumed.

My mechanic/friend in the local garage scanned it with his top of the range Snap-On reader and found no relevant fault codes were logged. Admittedly it's not VIDA but it is a top end bit of kit and he reckons, if a fault's been logged, it'll find it.

Additionally, I've noticed that DPF regens have seemed more sporadic/less frequent over the past 2 tank fulls of fuel - possibly relevant?

So I've been Googling and searching the forum here and came across a number of threads where failed DPF temperature sensors have been causing problems similar too mine. These threads all correctly state that there are 2 temp sensors in the system (1 actually in the cat and the other in the front of the DPF), however some have stated that if the 1st sensor fails you get no EML or faults logged and others say the same for the 2nd sensor. Hoping that this is in fact the cause of my problem (the sensors are relatively affordable), which one is it most likely to be? I am tempted to buy and try both but would obviously prefer spend as little as possible at this stage.

Any help much appreciated.

This fault happened on a few cars back then 12 years ago the stored fault code indicates which temperature sensor is faulty. you need to make sure there is a stored fault code.I cant comment on how good or bad non volvo general code readers are...

OK, thanks for the reply. There's actually a well regarded independent Volvo specialist about 6 miles from my work, I'll give them a call tomorrow and see if I can pop over for them to interrogate the ECU, it does seem strange that a limp mode scenario wouldn't log a fault.

As a follow up to this, I had Avalon Cars, a local-ish independent Volvo specialist have a look and run their diagnostics on on the car. VIDA came up with ECM-P004900 turbo over speed and ECM-P0023400 turbo over boost.

As a preliminary precaution, they carried out a smoke test and did locate a leak on the inlet side, between the air box and turbo which they rectified with the simple addition of some hose clips. I was then given the option of trying the car at that, or go a step further and replace the T-MAP (boost pressure sensor) on the intercooler as they're finding that these are now giving loads of boost related issues on many of the cars they're seeing. I opted to have them change it while it was there.

Only got the car back this morning but so far all seems good, in fact it feels to be pulling harder and cleaner than ever - despite having always been very happy with the performance of the 215hp D5. Time will tell, but hopefully that's the end of this little saga.