Check Engine Light- 4C52, 474D Codes- Resolution

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I thought I’d post a new thread on this issue- this issue has been reported elsewhere on the diesels, but not coherently.

Key Words:

Check Engine Light
4C52 CHARGE AIR TEMP. PLAUSIBILITY
474D INTERCOOLER TEMP. PLAUSIBILITY
2010 X5 35D diesel


The story:

My check engine light came on a few weeks ago. I pulled the code and found it to be an intake air fuel issue (generic code reader, my BMW reader will not work on the diesel).



I needed to have the first oil and DEF service done, so I took it to the dealership. 9600 Miles, Oilservice warning just started.

Tech reported an intercooler temp error. 474D. They just reset it, since there was no ‘active code’ (ie it wasn’t throwing it repeatedly) and BMW has no published service advisory for the 474D code.

I wasn't thrilled, but the tech had rarely dealt with diesels. We discussed it for a bit, and I pointed him to Xoutpost and BF for more details of this issue, including what solutions are being reported. He agreed to look into the issue. He was thankful for the heads up as BMW really does not provide dealers/techs with 'raw data'- they only get info when BMW has resolved an issue and has a solution.

Anyway the CEL came back on 4 days later on a Monday. Same generic code. I had actually pre-scheduled a visit this Thursday with a loaner …(knowing that the CEL might be a recurring theme, I had scheduled two visits on consecutive weeks just in case ). I do not like to be a victim, by booking I was protecting myself from the 'sorry we don’t have a loaner' dance. I live 45 miles away.

They had to keep the car for a while- they could not duplicate the failure, and went on to open a PUMA. They suspected a potentially ‘blocked’ intercooler. They removed and inspected the IC: fine. (Not an unreasonable query- If you have a blockage through the intercooler, the altered airflow can cause “implausible” temperature measurements.)

In the end, he replaced the intake temperature sensor and reprogrammed the DDE. Effectively following other reports of fixes for the ‘4C52 error’ that have been reported. Although mine was not the same error, it seemed to be a reasonable culprit… I promised to report the success of this fix.

Happy to report that so far it has been 12 days and no more codes.

I suspect a bad ‘batch’ of sensors. It is pretty easy to get a temperature offset in a sensor- a few degrees with the wrong solder or wire, or just improperly calibrated during sensor manufacture, such that the DDE is getting a value that is outside the operating envelope. It would be ‘silent’ too- the sensor is properly streaming data, there is no ‘open’ or short- just inaccurate. It will only show up indirectly when you need to ‘do’ something with the reading- in this case measuring the relative temperatures between (possibly) ambient or intake air and compressed, post turbocharger air.


A


PS Oil service done with no issues- SLX oil used, ~2.5 "units" of DEF (each unit is 2.5gallons) so a total of 6.5 Gallons of DEF used. No idea how much remained when they began the service.