Parking brake function - Correlation plausibility
â–¶ How to fix
Check TCM for leakages and/or blockages. Check piping between EPB and TCM. Replace TCM if no piping problem is found.
What you'll see
No driver-visible symptom recorded.
System reaction
Proportional braking may not work properly, under braked trailer (jackknifing) Yellow warning lamp.
Diagnostic depth
Detection
1. Demanded spring brake pressure differs from measured pressure more than a certain limit. 2. If spring brake pressure is under a certain value, yellow coupling line pressure has to be above a certain value.
Possible cause
Yellow coupling line pressure does not change as expected.