Cam Sensor A intermittent, with brand new sensors? No start :(
04-27-2017, 07:17 AM
#1
Cam Sensor A intermittent, with brand new sensors? No start :(
MY04 AP2, when I purchased the car about 40K miles ago it was obvious that someone had replace the cam sensor connector and about 10" of the harness with different wiring. Scarily enough they decided to make the splice about 2 inches above the main grouping of the wiring harness behind the valve cover going so far as to peel back the shielding on the green wire right down to the point when all the smaller engine harnesses come together. They had sadly used butt connectors and no solder, but the car ran fine and showed no issues for about 5k miles.
When it started occasionally throwing a cam sensors code for intermittent signal (p0339 I believe) I would just restart the car and it would be gone. Eventually it got to the point that it would happen weekly and I replaced both cam sensors and redid the wiring connections. Life was good again.for about 25k miles and its started doing the same thing, internittent cam signal on A. I had picked up some extra brand new cam sensors at a great deal so I tried swapping those in to no avail.
At this point she'll turn over good and strong, is getting fuel, and every one in a while will attempt to catch when you hold the start button for 5-6 seconds.
I hooked a lab scope to the output for the camshaft signal and it had a regular clean signal, the second time I hooked it up seemed to have an excessive amount of ripple between the AC phases during the downtime between when the magnet picks up one of the 3 tabs on the end of the cam shaft and the next tab . I tried the good old fashioned grounded aluminum foil wire shielding trick to see if I was picking up some interference somewhere but that had little to no effect. I finally decided to bypass the possibly terrible wiring the previous owner had done and run two new wires from the cam sensor and splice them into pins 20, and 21 (the Green and Red signal and ground wires for the CPS) at the ECM.
Still not able to get her to fire up properly. I've pulled the plugs, they were replaced about 6 months ago and other than being slightly covered in gas they seemed fine, cleaned them off and aired out the motor and still have the same problem.
Long story short: not sure where I'm losing my cam position sensor signal or if I've overlooked something, any suggestions or advice are greatly appreciated.
*Edit* Just went back out again after pulling the plugs again, airing her out, and double checking all connections. She tried to catch for about 1/2 a second with maybe 3 or 4 ignition events happening but then right back to cranking over with no spark. So damned irritating.
*Edit 2* if you unplug cam sensor A, she fires up instantly, runs smooth as can be, just throws a code for no cam sensor a (obviously) and is in limp mode. Gonna let her warm up and try it with the cam sensor hooked back up as that seems to be the time the engire fires up perfectly.
When it started occasionally throwing a cam sensors code for intermittent signal (p0339 I believe) I would just restart the car and it would be gone. Eventually it got to the point that it would happen weekly and I replaced both cam sensors and redid the wiring connections. Life was good again.for about 25k miles and its started doing the same thing, internittent cam signal on A. I had picked up some extra brand new cam sensors at a great deal so I tried swapping those in to no avail.
At this point she'll turn over good and strong, is getting fuel, and every one in a while will attempt to catch when you hold the start button for 5-6 seconds.
I hooked a lab scope to the output for the camshaft signal and it had a regular clean signal, the second time I hooked it up seemed to have an excessive amount of ripple between the AC phases during the downtime between when the magnet picks up one of the 3 tabs on the end of the cam shaft and the next tab . I tried the good old fashioned grounded aluminum foil wire shielding trick to see if I was picking up some interference somewhere but that had little to no effect. I finally decided to bypass the possibly terrible wiring the previous owner had done and run two new wires from the cam sensor and splice them into pins 20, and 21 (the Green and Red signal and ground wires for the CPS) at the ECM.
Still not able to get her to fire up properly. I've pulled the plugs, they were replaced about 6 months ago and other than being slightly covered in gas they seemed fine, cleaned them off and aired out the motor and still have the same problem.
Long story short: not sure where I'm losing my cam position sensor signal or if I've overlooked something, any suggestions or advice are greatly appreciated.
*Edit* Just went back out again after pulling the plugs again, airing her out, and double checking all connections. She tried to catch for about 1/2 a second with maybe 3 or 4 ignition events happening but then right back to cranking over with no spark. So damned irritating.
*Edit 2* if you unplug cam sensor A, she fires up instantly, runs smooth as can be, just throws a code for no cam sensor a (obviously) and is in limp mode. Gonna let her warm up and try it with the cam sensor hooked back up as that seems to be the time the engire fires up perfectly.
Last edited by Jdg784; 04-27-2017 at 07:59 AM. Reason: Addendum
04-29-2017, 04:45 PM
#2
Ok after countless checks of continuity, throwing her on a lab scope to check proper signal, test drives, and observing during various conditions....my TCT that was replaced with an OEM unit less than 10k miles ago had apparently decided to allow the chain ever so little slack. Not enough to make any rattle, except for today just above idle for a 1/2 second. I got to thinking and checked it against the scope at very slightly varying rpms just above idle.
The TCT would allow the chain to rattle JUST barely and was causing fluctuations in the cam sensor that were giving my ECM a headache. Swapped my old TCT (that was only changed as preventative maintenance) and BAM instantly back to a smooth running, smooth revving, beautiful SOB. SO long story short, if you are getting a cam code and can't figure that sucker out, CHECK YOUR TCT!
I would have thought it would require considerable slack to cause a variance in cam sensor output, but I would have wrong.
The TCT would allow the chain to rattle JUST barely and was causing fluctuations in the cam sensor that were giving my ECM a headache. Swapped my old TCT (that was only changed as preventative maintenance) and BAM instantly back to a smooth running, smooth revving, beautiful SOB. SO long story short, if you are getting a cam code and can't figure that sucker out, CHECK YOUR TCT!
I would have thought it would require considerable slack to cause a variance in cam sensor output, but I would have wrong.
The following 2 users liked this post by Jdg784:
JV-s2 (01-17-2024),
ROFL it's Waffle (11-15-2020)
11-15-2020, 05:14 AM
#5
Registered User
Ok after countless checks of continuity, throwing her on a lab scope to check proper signal, test drives, and observing during various conditions....my TCT that was replaced with an OEM unit less than 10k miles ago had apparently decided to allow the chain ever so little slack. Not enough to make any rattle, except for today just above idle for a 1/2 second. I got to thinking and checked it against the scope at very slightly varying rpms just above idle.
The TCT would allow the chain to rattle JUST barely and was causing fluctuations in the cam sensor that were giving my ECM a headache. Swapped my old TCT (that was only changed as preventative maintenance) and BAM instantly back to a smooth running, smooth revving, beautiful SOB. SO long story short, if you are getting a cam code and can't figure that sucker out, CHECK YOUR TCT!
I would have thought it would require considerable slack to cause a variance in cam sensor output, but I would have wrong.
The TCT would allow the chain to rattle JUST barely and was causing fluctuations in the cam sensor that were giving my ECM a headache. Swapped my old TCT (that was only changed as preventative maintenance) and BAM instantly back to a smooth running, smooth revving, beautiful SOB. SO long story short, if you are getting a cam code and can't figure that sucker out, CHECK YOUR TCT!
I would have thought it would require considerable slack to cause a variance in cam sensor output, but I would have wrong.
11-18-2020, 07:37 AM
#7
Registered User
52k miles, supercharged (stock ECU, using Vortech's conservative 8 psi setup). I can get a few good pulls in, but it's not predictable enough to pinpoint a recurring event. I don't have any starting problems, and extremely seldom rough running events (maybe 2 or 3 since I've owned the car (Feb 2020)).
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