Camshaft Sensor Issue

[disastrous-e30]

Hey guys,

I am new to the forum and I am having an issue with my car after wiring up the M52. I have exhausted all potential issues for the rough idle and I have settled on the Cam Sensor, not only because of the code but because of some items that I am about to describe. I first thought it was because I had a non-oem cam sensor so I changed it to two different OEM sensors and it still doesn’t work. I have tested the OHMs in the sensors of the Crankshaft sensor and the Camshaft sensor from the DME and I get 0.3 OHMs on both so I think that rules out any wire issues. Then I tested the volts on the Crankshaft sensor and the Camshaft sensor and I get 5v at the Crankshaft and 1.2 volts at the camshaft. From what I have researched it looks like I should probably get 2.5 volts at the camshaft sensor. This makes me think I have a bad DME. Any ideas or thoughts?

[Chilezen]

Are you running OBD1 or 2? What's the code you read? What else did you rule out? Why have you settled on the cam sensor? What are the other symptoms, and how long have they occurred? Is it a constant rough idle regardless of the temp?

[disastrous-e30]

This is a new swap so it’s actually hasn’t run well yet. It’s OBD2. It’s code P0340. I’ve settled on the sensor because of the difficulty to start the car as well as the rough idle which continues during warm up until it eventually dies. That’s the only symptom and yes it happens even if I let it idle for as long as it can. I’ve looked at all of the other items that may cause a rough idle and start up in the process and it’s none of the typical issues that happen to these engines.

[mjweimer]

Have you seen this thread?

https://www.bimmerforums.com/forum/showthread.php?2395865-S52-Camshaft-Position-Sensor

Lot's of really good info there and some great troubleshooting tips if you have access to a scope. Spoiler alert, he was seeing low voltage and a DME replacement fixed the issue.