ML420. Error code P2520 and P0105.

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V12cat

Member
Joined
Feb 8, 2012
Messages
41
Car
S500L, ML420, V12XJS, Pajero 2.8 SWB
Hi all.

Both these errors (P2520 and P0105) have appeared (possibly coincidentally) after an EGR delete remap (Avon Tuning).
Google has definitely not been my friend and has brought up wildly differing reasons for these codes and my code reader (Carly) isn't agreeing with google either.
One or both of these puts the car into a low power limp mode (usually with no engine management light) so is quite frustrating and they come up on most journeys, especially when idling.

P0105 Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction
P2520 The feedback through the transmission protection is not maintained.

I think these are the most likely to be correct code descriptions. I do have an independent Mercedes specialist in my nearest town so I could get a Star diagnosis which might be more accurate.

I've scanned the car numerous times in the past and these codes have never appeared before.

Is this something that anyone has come across before?

Thank you.
 
...to add to this, I've just taken it for a fairly lively drive and no limp mode but when I left it idling back at my workshop I heard the engine note deepen and it had gone back to limp mode, this time with a management light.

Same two codes.
 
...and the mapping tech said the vehicle already had a map on it. Not a good one, but I suppose they would say that. Given what I've read about swirl motor deletes etc I wonder if that is why this is happening. Maybe an incompatible gearbox map on it too? The car has got a pretty comprehensive service history but no mention of mapping.
 
I'd say your fault code definitions arent helping you to be honest. They arent codes I recognise as usual fault codes.

The MAP barometric pressure could indicate an air leak. My advice is dont delete anything further, let it collect data and then get it on Xentry.
 
I'd say your fault code definitions arent helping you to be honest. They arent codes I recognise as usual fault codes.

The MAP barometric pressure could indicate an air leak. My advice is dont delete anything further, let it collect data and then get it on Xentry.
Thanks for the reply.

My software actually points the p2520 code to the R48 thermostat heater.

The error codes don't seem to be causing the limp mode directly. If I drive and keep the engine speed above about 725rpm limp mode never happens and the vehicle performs as expected for 350bhp and 810nm. The codes still occur but don't illuminate the engine light. As soon as the rpm gets below about 725 you can heat the engine note change slightly and the manifold pressure drops from around 1125hpa to 800.
 
OK, a bit of feedback that might help others as there doesn't seem a lot of info about this sort of thing on MB forums. Avon tuning themselves were at a large agricultural trade show this week and I had chance to speak to them.

The new error codes could well have been intentionally suppressed by the previous mapping done on the vehicle. Hence why they appeared after my remap. Making their appearance related to but not due to my remap.

Feedback the technician got from them suggested testing the power to the manifold pressure sensor, which tested fine. But, they also said check the output of that sensor against atmospheric pressure, so ignition on but engine not running. There are three other sensors on the car that also would be at atmospheric pressure at rest and here is where a discrepancy showed up. The inlet sensor and both exhaust back pressure sensors showed similar readings but the manifold sensor was about 90mbar higher. Not enough to bother the engine when running off idle with some boost (and didn't cause any discernible smoke) but enough to throw an error at idle.

I had tried a new sensor but that made it worse. Transpired I had been supplied the wrong sensor. Anyway, correct new sensor and it doesn't go into limp. Guessing but not checked that the R48 thermostat sensor error is still there.

The Avon Tuning map is a lot smoother and much more progressive than whatever was there before too.
 
It's very possible. Engine maps are a funny business. Some people claim to be "mappers" just load generic maps to ECUs where the range factors are so extreme it prevents fault code reporting. I have certainly had that experience before many times.

Personally I always use GAD tuning, despite their distance from me. Their map files are excellent and not extreme that it prevents fault code reporting.
 

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