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1999 Audi A4 1.8T Misfire and Throttle Position Code P0302 & P1505 - How to Fix Without Going to the Shop?

Model: 99 A4 1.8T Fault Code: P0302 Posted: 2010-04-05 06:56

I currently have two diagnostic trouble codes appearing on my 1999 Audi A4 1.8T: P0302 and P1505. I'm trying to resolve these issues myself before taking it to a mechanic. P0302 indicates a 'Cylinder 2 Misfire' condition, which can be caused by an ignition system fault or a fuel injector issue. P1505 points to a 'Closed Throttle Position Does Not Close/Open' problem—this could stem from an open or short circuit in the throttle position sensor or a failed closed throttle switch. In addition, my turbocharger is not engaging, which I've been told is normal and should resolve once these codes are fixed. However, I'd like to understand what steps I can take to diagnose and fix both issues effectively.

Related fault codes

P0302P1505

Comments (2)

Anonymous 2010-04-05 13:55

Just a quick note—I suspect there might be a vacuum leak in one of the hoses. Vacuum leaks are known to trigger misfires, especially with codes like P0300 or P0302. While a single misfire could be temporary, could it potentially lead to more serious long-term engine problems if left unaddressed? Any experience with vacuum leaks related to these codes?

Anonymous 2010-04-18 01:31

The spark plugs and ignition coils used in the 1999 Audi A4 1.8T are known to have reliability issues, and some models were part of a recall (GFL). Try swapping the spark plug coils between cylinders #1 and #2. If the code shifts to cylinder #1 (P0301), replace the coil for cylinder #1. If it stays on cylinder #2, then the issue may be with the spark plugs themselves. Vacuum leaks can cause random misfires (P0300), so checking for such leaks is a good first step. I'm less familiar with P1505—anyone else have experience with that code?