Check Engine light vs fault

[Andrew1972]

I have a 2018 Tiguan and the only very occasional issue is backing up with a cold/cool engine it hesitates and near stalls and then catches back. It has never illuminated a check engine light.

Does the computer store codes but not illuminate the check engine light?

There is a specific TSB for this and would like to get addressed:

 

[atikovi]

Originally Posted by madRiver
Does the computer store codes but not illuminate the check engine light?


Sure does. Could have pending codes stored that won't illuminate the CEL, yet. Could have transmission codes stored some of which won't illuminate the CEL.

 

[mk378]

If the ECU loses memory backup power it may run badly the next time the engine is started until it can recalibrate. The only other symptom of that would be the emission ready codes become not ready for a time. To troubleshoot a highly intermittent problem you really should have your own code scanner.

 

[Andrew1972]

Originally Posted by mk378
If the ECU loses memory backup power it may run badly the next time the engine is started until it can recalibrate. The only other symptom of that would be the emission ready codes become not ready for a time. To troubleshoot a highly intermittent problem you really should have your own code scanner.


I understand for self diagnosis however this vehicle is covered by a 6yr/72k mile warranty. My hope is faults not CEL are in fact stored. I am unclear if a dealer will perform a TSB unless there is actual fault they can reproduce or diagnose.

 

[Mad_Hatter]

Originally Posted by madRiver
I am unclear if a dealer will perform a TSB unless there is actual fault they can reproduce or diagnose.

They won't. A TSB isn't an actionable item until there's a bona fide fault.

If you don't have an OBD2 go to AZ and see if they can pull up any pending faults.

It would be nice to know if your O2's are still in closed loop when this happens. In closed loop you're running rich, maybe the rich air/fuel is causing a stall?? With an OBD2 you could monitor such things in real time.

Just a hunch...idle control maybe? At cold startup you're idling high then you put it into gear and the rpms drop too low, momentarily, causing it to almost stall out??.. check out the rpms change from P to D when cold...is it dipping well below 600 rpms for a moment?