Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
2005 Volkswagen 2,0 TDI (PD injection),automatic. Cranks but wont start intermittently, No DTC , Run engine for 5 min plus switch off, Restart vehcle just cranks but wont start. Key on engine off radiator fan runs on cold engine. Wait approx 10 min vehicle will start or switch Ign on and off a few times. When engine is at operating temp and you switch off, waiting period before she will start approx 30 min to 1hr. While she cranks with non start and scan tool connected, all sensor values/numbers do not show, it is blank.The automatic shift indicator on cluster also flash. Main relays check out okay. When back on vehicle again will be checking power and ground to ECU while there is a non start. Just off the top of head, power to the ECU is being pulled to ground. Any advice would be real welcome
Euro cars, I don't like them at all! Too much finicky electronics.
Check all fuse connections too. I had an Audi A4 that would occasionally stall and bring up "short circuit to ground" faults on all the major engine components including injectors. I traced it back to a single 25 amp fuse that had a bad contact in the fuse box - burned on the sides. Every now and then it had a voltage drop that made the ECU assume that there must be a short somewhere. Running your hands across the fuses sideways can show up a bad contact.
Getting involved in discussions because I have a lot to learn still.
The immo system features a lag function. On these # 4 and ยท# 5 iimmo types there is no key identification request after engine shutdown for some 10 seconds on restart. Any key ,even without transpoder, will start the car during this period.
So if the engine does not start IMMEDIATELY after shutown this points into another direction than immobilizer.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
