Code 31 - Camshaft Sensor

[A26B]

Originally Posted by crjspo23

So I assume you have to take the aluminum cover off to get to the MAP hose?

Thanks for the advice on the cam sensor connector. I'll try that.

Here is a picture of the MAP hose Tom is referring to.

[tomtom72]

Originally Posted by A26B

Tom, I just gotta say, any ZR-1 would be lucky to have an owner like you! Mine are badly neglected compared to the treatment your ZR-1 receives. You are the top PM guy in my book!

You make me blush Jerry! I would like Her Majesty, Mistress, to read your post if that were possible. She is giving me the evil eye lately since my PM operations have moved outside to my parking space. She rather takes exception that She's not being worked on "indoors" so to speak!


Tom

[crjspo23]

Well Tom, looks like I'm not that lucky. I serviced the sensor connector as you said, checked and cleaned the MAP sensor hoses, reset the ECM, and got the SES light back when I restarted it. Got the same code 31. Looks like I need a new sensor. Anybody know if the camshaft sensor is still available thru GM or elsewhere?

[Mystic ZR-1]

31 was one of the many spurious codes my car had before injector
replacement. "Ohm out" your injectors before you get too carried away
replacing stuff. You can find out how to do it in the FSM
or somewhere on this site. Anyone know where it is in the site?
It seems after hanging around our site for a few years now, that
injector replacement cures most of the crappy running ills that 90 and 91s suffer...

[Hammer]

Originally Posted by Mystic ZR-1

31 was one of the many spurious codes my car had before injector
replacement. "Ohm out" your injectors before you get too carried away
replacing stuff. You can find out how to do it in the FSM
or somewhere on this site. Anyone know where it is in the site?
It seems after hanging around our site for a few years now, that
injector replacement cures most of the crappy running ills that 90 and 91s suffer...

This thread might help. GL
http://www.zr1.net/forum/showthread.php?p=17299

[tomtom72]

Hi Charlie! Nice to make your acquaintance! I just checked over at RockAuto and they list one. You could contact Jerry at jerry's gaskets or Kurt White at White Racing to check to see if they have any NOS on the sensor.

Humor me for a moment, even tho I'm a bit eccentric. This sensor is an electro magnet and a reluctor wheel. I would pull the sensor from the head and check the face for sludge or dirt or anything that could weaken the magnetic field. Okay that's just me because I don't understand how an electro magnet breaks, sorry. Now mind the spacer that I think should be present to keep the correct gap between the magnet and the wheel.

Also, if you decide to ohm out the injectors using the ECM main harness plugs be aware that you can/should not use the probes from your VOM directly into the harness plug cavities. Those probes are just a bit too big to fit into the female terminals with out distorting them. You don't want that to happen. I'd use some phone wire to probe the cavities and then touch the VOM probes to the wire. If you spread those terminals even a bit you get an intermittent contact at the harness plug and it drove a member crazy with weird symptoms. Search threads under "TCrabs" to find his story. I just related the short version.

On another note. Is there another brother near you that would be willing to let you use their ECM. I had one of my ECM's go bad and give me a DTC61 and after pulling the plenum to check all the electricl aspects of the flow chart I found it to be the ECM and not any parts on the motor. Just bear that in mind. I don't have my FSM handy to look over the DTC diagnostic chart for #31 so I don't know if the ECM is listed as a suspect.


Tom

[crjspo23]

Seems to get more complicated by the minute. Anyone know a knowledgeable Z mechanic in the Piedmont area of central NC I could take it to?

[tomtom72]

I don't know of anyone that I could send you to. Are you anywhere near Hendricks, he owns the snake skinner car so I would think he might have some one familiar with an LT5 on his staff. That's just a shot in the dark on my part.

However if you are inclined to want to do this yourself we are standing at the ready to render any assistance we are able to thru this forum. If you were a bit closer I'd just drive over with my stuff and we could see what's up. Are there any other Z Brothers near you?

Also forgot this. I never actually found the reason for my car giving me the DTC 31. I noticed one thing that was consistent about the episode though. It seemed that if I altered the way I start my car I could avoid getting that DTC. Yes, weird right? I learned to not be in a hurry when starting her. Now I turn the key to "on" and light up the DIC, wait till most of the lights go off, and then go to "start". When I wasn't doing that I would get the 31. Yea I know I should pull the cam sensor and look at the face or just buy a new one. I'll get around to it eventually I guess.


Tom

[crjspo23]

Guys, need some more help. I took my car to a mechanic that knows Corvettes well but is not expert level in ZR-1's. He has confirmed the cam sensor is not causing the problem (tried a new one with no change) and also confirmed 2 injectors are bad after ohm testing (#1 and #2 primary), but he says he can't check the secondaries without removing the plenum and he is not convinced the injectors are the only problem.

Any other ideas or advice to isolate the issue?

[A1990]

The overriding consensus is that if you have a bad injector, that you replace all of them.

Order a new set and pull the plenum and check other parts "while in there"