91 Buick Regal, how to diagnose trouble code 41
 

Hello. I have a 91 Buick Regal with the 3.8 engine and an aftermarket natural gas (LPG) system.
One or two seconds after engine start the service engine light comes on. When i blink out the codes it shows 41 which could be:

• no distributor signals to ecm, or faulty ignition module ( carbed models)
• cylinders select error- mem-cal or ecm problem ( fuel-injected models
• cam sensor circuit (3.8 engine)

I was also thinking that the seperate (E)CM of the natural gas system could make this code show up, but i'd rather vertify that its nothing else.

The engine has a slight missfire when it runs on gasoline, and when the car is on operating temperature, and its running on LPG, it has a bigger, more noticable misfire (Often a sign of bad ignition, since LPG is harder to ignite. Spark problems show up earlier on LPG than on gasoline)

I am not a pro when it comes to electronic stuff, but i know how to turn a wrench, and i can follow good instructions precisely.

What would be the first step to diagnose a trouble code 41 ? Which cause is the most common one, and how can i test them step by step?

It would be great if i could receive help [img]data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7[/img]:)

Greetings, Jack

So its more likely being the fault of the camshaft business? Because of my natural gas system, its kinda diffucult to get to the camshaft position sensor. Would it be possible to test if theres a signal coming from the sensor without disassembling it? Like backprobing the wires to see if theres a voltage change or an resistance test or something like that? If yes, what color do these cables have, and where do they lead to?
Greetings Jack