[remocmij]

I have a 96 passat TDI that is going into limp mode. sometimes the check engine light comes, sometimes it doesn't. tried to scan for codes but unable to link to the ecu. replaced all the vacume hoses, including the one in the ecu. but no change. changed the n75 soinoid and the egr solinoid. still no change. cleaned the intake manifold , still no change. don't know where to go from here. I find it very frustrating not been able to access the ecu and check for codes, because i don,t like changing componants as a form of troubleshooting. any suggestions would be apprieceated
thanks

 

[Fluid]

Hm, limp mode is caused by the ECU sensing a problem with fuel, air, or engine.

You;ve fixed teh vac hoses the solenoid.

There shouldn't be a problem with air. At this point, if your car otherwise runs fine, get a boost gauge. Tap a vac line for boost and run it into the cabin. During normal driving, check if it's overboosting. If it is, the problem is with air.

No bubbles in the fuel line? It could be a problem with the injection pump. When was the filter last changed?

 

[remocmij]

fuel filter was the first thing i replaced. it is fine with no air bubbles in the fuel line. do you tap into the boost line at n75 solinoid?

 

[chittychittybangbang]

Tap into any intake manifold vac line. So any line that comes off the intake path downstream of the turbo and intercooler should work. I wouldn't tap into the line that goes to the ECU just in case it leaks or causes an issue with normal sensor operation. What ECU part number do you have?

 

[wren53]

could a bad turbo cause limp mode?