Case Study: P026A on 2012 Passat TDI (CKRA)

[Jef]

ST?ID=104013

2012 Passat TDI, CKRA engine w/ DSG transmission

Cust states engine would start and run fine, but put into gear and engine would bog down and die. Difficult to free rev engine, 2500 to 3000 RPMs tops.

P026A 000618 Charge Air Cooler: Efficiency Below Threshold
P0101 000257 Mass Air Flow Sensor (G70): Implausible Signal
P2209 008713 Sense Circuit for Heater for NOx Sensor 1 Bank 1: Implausible Signal

Unplugged MAF, cleared DTCs several times in a row, no change. No restrictions with the exhaust system. No restrictions found for intake side or intercooler. Fuel filter was replaced prior to calling, no glitter / metal shavings in fuel system.

Further digging found the following in live data:
IDE04938 - Sensor for temp after charge air cooler: raw value = 110°C

Looking at other examples of known good engine with location IDE04938 - Sensor for temp after charge air cooler: raw value, the highest value found was 55C, most were in the 30C range.

This data is from the G42 sensor (G42 / G31 / GX9) in the wiring diagram. Electrical paths to the sensor (wiring / terminals) were to factory design. Sensor was just reading a stupid high value. A new sensor was installed, DTCs cleared a few times and the engine is currently working to factory design.

Another classic case of "fixing cars is easy, diagnosing them is the hard part".

 

[Uwe]

IDE04938 - Sensor for temp after charge air cooler: raw value = 110°C

Well, that certainly explains why the ECU thought that the intercooler's efficiency was not up to snuff!

What's a bit sad is that the ECU doesn't recognize this as an obvious issue with that sensor, say right after a cold-start, when everything else is at 30C or less, and that sensor is still at 110C... "Hey, there's something wrong with that sensor, not the intercooler itself!"

-Uwe-

 

[Jef]

.... again, our consulting fees are very reasonable but no one from VW / Audi has taken us up on our service. How about this, Mr Diess, contact us and we will do a free consulting session, no obligations. I think you will quickly find we bring a lot to the table. Maybe afterwards, we can go get some hot wings or tacos, our treat.

 

[Jef]

ST?ID=115549

Another one... 2013 Passat TDI, lacks power.

P0111 - Intake Air Temperature Sensor 1 Circuit Range/Performance; Bank 1
P0101 - Mass or Volume Air Flow Sensor "A" Circuit Range/Performance
P026A - Charge Air Cooler: Efficiency Below Threshold

key on, engine off:
IDE04938 - Sensor for temp after charge air cooler: raw value = 105C
That value is generally 50C range or less.

Tech verified wiring for G42 / G31 / GX9 that is at the top of the intercooler was to factory design, no wiring issues found. A new sensor was installed and that fixed the issue.