Cam Position Sensor Replacement

[jmb952]

1999 996 C2 Coupe, 6 speed

First off, I am new to this forum and wanted to say hello to all. After having owned several Porsches in the past, and having been without for several years, I am very happy to say that I am once again a Porsche owner! Unfortunately, I have an issue that needs resolving...

My 996 is idling rough and threw a P0341 code...Bank 1 cam position sensor.

According to the pics I've seen, it seems to be behind the AOS. How difficult is it to check and/or replace this sensor with the engine in the car? What is the best way to get to the sensor and how much disassembly is required?

Thanks.

[Jeremy Cottrell]

Bump for any tips.

[Peterfrans]

Bank 1 cam sensor is on cilinder 1, not on the flywheel side

[Dharn55]

Unfortunately Peterfrans has it wrong. On a 996 USSpec bank 1 is on the drivers side, at he top of the cylinder head toward the front off the car. It can be a pain to get to with the engine in the car. Probably the best way to get to it is from beneath the car. I can send some pictures if that will help. On early 996's, 5.2 DME there is only one cam position sensor. On the 7.2DME there is one on each cylinder head.

[injurylawyer]

Unfortunately Peterfrans has it wrong. On a 996 USSpec bank 1 is on the drivers side, at he top of the cylinder head toward the front off the car. It can be a pain to get to with the engine in the car. Probably the best way to get to it is from beneath the car. I can send some pictures if that will help. On early 996's, 5.2 DME there is only one cam position sensor. On the 7.2DME there is one on each cylinder head.

 

I purchased a '99 996 C2 in October 2014. Never been in an accident. Less than 10k miles before I purchased the car, the engine was replaced on the car by the previous owner professionally with a complete rebuild using a '01 block, L&N Engineering Nickies upgrading the bore from 3.4L to 3.6L, forged pistons and their IMS upgrade.

 

The car runs great but I have the P0341 code and the CEL on. After discussing same with the prior owner, who essentially owned the car for 13 years, it was not on supposedly after the rebuild but perhaps about 5k miles later when it started. The prior owner had the very reputable shop that rebuilt the engine replace the sensors, check and redo the timing, replace the tensioners, etc. and try to trouble shoot the issue to no avail. Even the DME was sent out to be tested and came back just fine. Money was really no object for the prior owner (lucky him).

 

The master mechanic who did the work tells me the car is running great, nothing is otherwise wrong and I should just enjoy driving it...

 

I took it to another PCA member recomended Indie for a second opinion. After $1,200 in electrical troublshooting (that was discounted) and sending the DME out again to have it come back good yet again, the only advice given was the possiblity of replacing the entire engine harness---an expensive proposition without a guaranteed result.

 

I have continued researching the issue and even come across an article stating sometimes, in some models, low battery voltage or a weak starter can even trigger a CPS code.

 

Porsche's owne OBD II definition of the code for this model is 'Camshaft Position Sensor 1-Signal Implausible, Short to Ground, Short to B+'.

 

So, it seems to be an electical issue...

 

FYI-the alternator-starter Y-cable (part no. 99660701903) was just replaced because of a low voltage issue I was having only 5k miles after the alternator was replaced along with an older version of the Y-cable (99660701901). The car is putting out the proper voltage even under a heavy load now...

 

Regardless, the interesting thing about your post from 1 1/2 years ago, Dharn55, is that you mention the 5.2 DME having only one CPS...I have that DME but the engine is a '01 that likely had the 7.2 DME which you indicate there is one on each cylinder head. However the swap retained the intake plenum from the original engine since it is drive by the wire rather than the later E-gas version of the throttle rather than retro-fitting the entire car for E-gas (like changing the pedal to electronic, changing the DME to 7.2, etc.). Looking under the car, there appears to be CPS on the passenger side...

 

Any thoughts/insights would be appreciated.

 

:help:

[Ahsai]

Have the shops checked the big round connectors in the passenger side engine bay? You can buy a can of Deoxit, disconnect the connectors and spray the pins. Some of the pins may be corroded.

What's the cam deviation read out?

If the DME sets that code, that means the DME can't see the signal from the sensor (barring any faulty DME). It could be intermittent. If it's intermittent, it will be more difficult to troubleshoot becasue the fault may not be there when the tech is checking and that could lead to wrong conclusion.

Have you tried resetting the code and see how soon it comes back? The sooner the easier to diagnose. One way is to tap into the DME pins and hook up an oscilloscope to monitor the signal in real-time to check for signal dropout. Even take the car out to a test drive. If it's intermittent, you can wiggle the wires and see if that changes anything.

[injurylawyer]

Have the shops checked the big round connectors in the passenger side engine bay? You can buy a can of Deoxit, disconnect the connectors and spray the pins. Some of the pins may be corroded.

What's the cam deviation read out?

If the DME sets that code, that means the DME can't see the signal from the sensor (barring any faulty DME). It could be intermittent. If it's intermittent, it will be more difficult to troubleshoot becasue the fault may not be there when the tech is checking and that could lead to wrong conclusion.

Have you tried resetting the code and see how soon it comes back? The sooner the easier to diagnose. One way is to tap into the DME pins and hook up an oscilloscope to monitor the signal in real-time to check for signal dropout. Even take the car out to a test drive. If it's intermittent, you can wiggle the wires and see if that changes anything.

 

Not certain as to the cam deviation read out...

 

The big round connectors in the passenger side engine bay....not sure which ones you may be referring to. If you have a little more for me to go on, I will check that out since I have a can of Deoxit in the garage...that would help me pinpoint where it is since it sounds like somthing I can try.

 

Yes, have tried and they have tried resetting the code. It comes back every 10 to 25 miles. The second opinion garage inidcated when testing the CEL was off for almost a couple of days on one test round (they had the car for nearly 4 weeks since they were not charging me full rate, they were testing same during down time on other projects).

 

Ahsai, thanks for your input on this post too...

[injurylawyer]

Have the shops checked the big round connectors in the passenger side engine bay? You can buy a can of Deoxit, disconnect the connectors and spray the pins. Some of the pins may be corroded.

What's the cam deviation read out?

If the DME sets that code, that means the DME can't see the signal from the sensor (barring any faulty DME). It could be intermittent. If it's intermittent, it will be more difficult to troubleshoot becasue the fault may not be there when the tech is checking and that could lead to wrong conclusion.

Have you tried resetting the code and see how soon it comes back? The sooner the easier to diagnose. One way is to tap into the DME pins and hook up an oscilloscope to monitor the signal in real-time to check for signal dropout. Even take the car out to a test drive. If it's intermittent, you can wiggle the wires and see if that changes anything.

 

Looking at the engine bay, I think I see the two large connectors on the passenger side, just below the high pressure hoses....they seem to have some form of round twist connectors but I am uncertain how to disconnect them to inspect and spray...

[Ahsai]

Just twist anticlockwise to unscrew them one at a time so you don't confuse between them as they are interchangeable.

Due to its intermittent nature, it will be quite difficult and time consuming to troubleshoot.

Btw, even if the wiring to the sensor is an issue that can't be tracked down, you don't need to replace the whole engine wiring harness. Someone just need to put some new wires and sensor connector directly between the DME and the sensor (remove and replace the relevant two pins on the DME connector) to bypass the questionable existing wires and sensor connector to the sensor.

Edited May 9, 2015 by Ahsai