Check engine light help
 

Check engine light came on this morning after starting car. 28k mile 08 C4S with no engine mods other than X51 airbox with dual snorkles. Dash warning says emissions fault-have dealer check.

Car ran fine yesterday morning going to work. A little over half way into a full tank of gas 5-6 days ago from usual source. It rained very hard yesterday for awhile while parked outside my office. When leaving work car didn't turn over after usual short crank, and I had to try 3 times to start but then seem to run fine on way home, however 2 things happened for first time. One, cruise control wouldn't work but had worked same morning on last drive. Second, the tach needle above 2700rpm jumped around 1-200rpm when cruising or accelerating at/above that level. Car was never in any limp mode and no warning came on yesterday. I had to crank starter once for about 5-6 seconds today to start on first attempt. Engine sort of sputtered for 1 seond at start and engine light came on after maybe 10 seconds but no strange engine sounds after started and was idling fine before I shut it off.

Any ideas would be appreciated. I don't have OBD reader, but if safe I can drive 2 miles to auto store to have checked. Could be gas cap I guess, but that doesn't explain new issue with tach and cruise control. Maybe water made it somewhere it shouldn't. Can't think of a way to tie all 3 issues together since all happened within 12 hours.

As long as it's not a flashing CEL, you can dirve it to get the code(s) read. GL.

Thanks, I'm pretty sure it was solid engine light and !

I called the indy a mile from my home, and they of course just want me to drop if off, which I will do depending on what OBD scan shows code wise. Mechanic mentioned a bad alternator can sometimes cause these multiple issues including rpm fluctuations.

Certainly an alternator can cause all kinds of seemingly unrelated electrical and drive-ability issues to arise. But since you mentioned emissions fault, combined with heavy rain, it may be as simple as replacing a coil pack. Pretty simple job if you can contort your hands and have a universal joint socket. Get the codes read and report back. Misfire in a cylinder should be easy to diagnose. Good luck!

I went to get the code read at parts store since it was closest.

The only code was P0335 which appears to be crankshaft position sensor circuit A. That explains check engine light which stays on without blinking. Car was difficult to crank over but ran fine once going, although I drove the 5 miles nice and easy.

Does anyone know if this could account for other symptoms including mild rpm fluctuations and cruise control not engaging? I'm hoping so. If it's an alternator issue I suppose it could cause some or all of the issues, but frankly I don't know. I'll do some research and search the forum now that I have a code at least.

If it is just that sensor, has anyone replaced one? Wondering if it is easily accessible or buried deep.

I could try to swap them if they are pretty easily accessible . I haven't found a DIY for this anywhere yet. Any suggestions where to look since I don't have a shop manual?

Here's an article that shows the location of all the critical sensors in a 997

A cam position sensor could cause all of these issues. When one fails completely the tach needle won't jump as you try to start the car - it should bounce up and down as the engine rotates on the starter.

If you had a Durametric you could look at camshaft deviation on both banks and determine which one wasn't working.

Here's what mine looked like when it went bad earlier this year. The one showing all zeros is the failed one. I bought 2 and now have a spare in case the other one fails or one in my wife's car.

https://cimg3.ibsrv.net/gimg/rennlis...c31ce48ab6.png

Since my code is for crankshaft sensor instead of camshaft sensor, would I see an abnormal reading for camshaft deviation? At this point I'm assuming most likely issue is what the code was for or maybe alternator issue. I assume if it were a bad camshaft sensor I'd get a code for that, and I'd get a different code if it were a bad coil pack. The battery is 6 months old and car used daily, so that shouldn't be any issue typically.

yeah, seems there is only one crankshaft sensor unless I'm mistaken, and seems to be accessible from either a wheel off or from below.