Hey guys,

So heres the story with my 90 SSE. I just got it a few weeks back and it had a bit of a rough idle. No check engine light was on. I drove it for a week, then next fill up I put some fuel injector cleaner in it. About 10 minutes after I did that, the service engine light came on. I wasn't too worried about it since I had new plugs, wires, coils, icm, o2 sensor waiting to be installed. Well I just installed all of that (and the battery was out of the car) and I start back up and I still have the light. Pulled the code tonight and its a code 41, "Cam Sensor Circuit."

Just wondering what I'm supposed to do about this. Car runs great, except for a bit of a rough idle. And when I go to start it, it fires right up but I have to give it a little gas otherwise it dies right away (sometimes) while I never had this problem before. Acceleration is smooth, highway driving is fine, its pretty much just my idle thats messed up. I was going to change the cat yet, as I think the stock one is on (225000 miles) but other than that I'm out of ideas.

Thanks in advance
-Bob

When mine chunked the cam sensor magnet (that is mounted in the cam gear), my idle was rough and it ran a little weak. If you pull the passenger front wheel and the fender liner, you can get a good view of the cam sensor. Pull it, and turn the engine with a large wrench on the crank bolt clockwise until you see the magnet or its empty hole in the cam gear. If there is no magnet, you need to get a new one in there. Hopefully the magnet is still there, because the sensor is much easier to replace.

OHHHH, the dreaded code 41. I hate that code.. You'll know why in a bit.

The cam sensor, which is mounted on the timing chain cover, gets its signals from a magnet encased in plastic, in the camshaft timing gear. This is the chain driven camshaft, its the gear, that holds the magnet, and sends the signals to the ECM.

The problem with this design, is the magnet is encased in plastic, and plastic in an engine? Not good, it breaks down, and at the right moment, flies loose, (usually after you've done some racing with it, lol)

Shops charges vary arounds 500-900 dollars for replacement. The timing chain cover, waterpump, harmonic balancer, and everything else on the front end has to come off to get to the magnet. To replace the magnet, the cam gear has to be unbolted from the camshaft, which means, you'll have to line up the timing marks on the crank and cam gears. Its a big job. I was able to do this in 8 hours, with power tools.

You'll have to go to the dealer and get a new, as GM calls it, an interrupter. Also get a set of front end gaskets, and some permatex ultra copper sealer.

There are guys on the board who will chime in, they've done a cheap and easy way to replace the magnet---I don't recommend it, especially if you really rack up the miles on the car, theres no telling how long that job will hold up. The best solution is a dissassembly of the front end and replacement of the magnet.

Of course, you can do without. Its only there for the proper sequence of the firing of fuel injectors. The ECM will instead take the reference signals off the crank sensors to determine the firing of the injectors. It isn't exact, and as SFI (sequential fuel injection) performance suffers, your gas mileage is affected too, and the car may run like poo poo sometimes. I didn't notice much of a difference, but did notice gas mileage wasn't as great. I had to drive like this for 2 weeks till i could get the $$$ for parts, then i finally did it. I just hate check engine lites, lol.

Anyways, good luck, and any questions, just ask.

Well I'm pretty sure I know when it happened. Took about a day for the code then however. I was sitting at a stop sign waiting to turn left. I punched it and the car just went POP! and died... I was thinking ok... Started right back up and didnt drive any different... I thought maybe that had something to do with the injector cleaner I put in there... either way I know the last people must not have pushed the car too much.

I got some work to do on the gtp, so this code 41 crap will have to wait a bit... I'm not too excited about changing that sensor either after reading and doing a more thorough search on this topic :(

The sensor is the easy part. It'* the magnet on the cam gear that is a pain.

Not if you use an impact wrench. I've seen electric impacts at Wal Mart and Harbor Freight that can do the job without breaking the bank.
Remember, on these cars the crank pulley bolt takes 220 ft. lbs of torque.

Why not do the Padgett Fix on this problem. It worked me.

http://www.6007.us/

Click on the abouve URL then go to "Cars, Musings, and misc". Then click on "Assorted Articles, Code Deciphering, and Musings". And finally "Simple Cam Magnet Replacement on a 3800".