I have a 95 z28 with a brand new rebuilt motor and transmission. Just got it running this past saturday. No problems at all. Drove it down the road and got on it a little bit and returned home and left it idling. After a few minutes car started reving up on its own and then would idle up to 2000 rpms and then back down. I got back to car and sat down and then pressed accelerator pedal and car died. It has not started back since. It tried at first now it wont even try. Its leaving a code 16. Is this faulty opti or faulty pcm any suggestions. Thankx

 

Opti or opti harness. Clear the code and see if it returns on cranking.

 

The low res signal from the opti to the PCM through 3 different connectors. Any where along that path it could be a problem. First place to start, pull the connectors starting with the opti and look at the pins on both mates.

If all that looks good check from the pink/black to the red wire at the opti for the presence of 12 volts with KOEO.

Then check from the red/black to the pink/black for 5 volts same KOEO.

 

I replaced the opti and the harness and still nothing. I also replaced the coil and still nothing. So gonna have icm or module checked today. If its not that then its the ecm i guess.

 

First of all the ICM and what ever module you're talking about have nothing to do with a 16. Nor does the coil.
Second why did you ask in the first thread if it could be the opti only to say in the second thread that you changed it??????
Third, did you change BOTH the small 3 foot harness and the entire front body harness?
Last, are you against doing measurements? Seems you only want to throw parts at the problem.
I have yet to see an OBDI PCM defective.

 

I was told by the Chiltons manual is was probably the opti in BOLD Letters and by the way it was a day later when I reposted stating i changed the opti and the coil. I also had the ICM checked and It checked bad so I apologize for wanting some smart advice not smart alek advice. I guess replacing the body harness isnt throwing parts AT IT????????? I also tried clearing the codes with my POS code reader from Oreilys and it does nada. So I dont know if its resending the code or not. I've disconnected the battery for 2 days and I'll check this weekend.

 

I did check the opti harness and it checked good i couldn't check all the volts i was just borrowing an opti for the evening till my new one come in. I didnt trust my old one when i put it on. It had slack and 180,000 original miles on it to all of my knowledge. I changed the cap and rotor before reinstalling it and thats it. I put new wires and plugs on it. When I get my new opti I'll check the voltage at the opti harness. Like I said it ohmed out good.Thanks again for all your help I'm tired of workn on it just want to drive the heck out of it and order some NOS.

 

You can clear the codes quickly by pulling the "PCM BAT" fuse in the box under the hood for 30 seconds. That will tell you if DTC 16 is a stored code or an active code. Disconnecting the battery for 30 seconds will achieve the same results.... you don't have to unhook it for "days".

You're not going to get much help if you attack the people who are trying to help you. Its very frustrating when you try to help someone, and they ignore your advice, and then start adding information that they failed to provide in the original post. You also need to state very clearly, and very completely what you have done. I'm still not sure what you have in the way of an Opti after reading your posts. Sounds like you installed a borrowed, used Opti with a new cap and rotor, and have a new one on order, but not received. Was the borrowed Opti out of a car that was running, or could it possibly have optical sensor problems too?

You can check the voltage between the low res signal wire and the reference wire (since you have a Chiltons, you have the colors), and as you slowly rotate the Opti on revolution, you should see the voltage switch between 0V and 5V 8 times. That would confirm the presence of the low res signal. DTC 16 sets when the PCM does not receive that signal.

 

I replaced the borrowed opti with a brand new one. I also replaced the bad icm(had it checked at oreillys it failed at low and high rpm). I installed the new opti and icm and the car hit once and now nothing. I ran the new codes and i have a 41. I also have a 34 but I don't have the whole intake system installed so I suppose thats why it set that code. Still don't have a clue. I'll check the voltage as soon as i give up the idea of crushing the car monday at the recyclers. Thanks for the help that last post was very helpful and informative. I need it spelled out for me in plain words like you did thanks. Like I said first computer controlled car to work on. Have a nice weekend.

 

Here's the code list, specifically for LT1's.

http://shbox.com/1/Dtcs.htm

DTC 41 indicates you have a problem with the wiring to the ICM. Typical causes can be:
-short to votage on the IC circuit
-open IC circuit between the PCM and the ICM
-open ICM ground circuit
-faulty circuit from coil to ICM

Here's the schematic for the ignition control circuit (courtesy of Shoebox):

http://shbox.com/1/95_ign_system_schematic.jpg

DTC 34 indicates a problem with the MAP sensor or wiring. The code sets when MAP drops below 14kPa, which corresponds to more than 28"Hg vacuum. This can be due to an intermittent circuit on the lt green signal wire or the gray 5V reference wire to the MAP sensor. Start by checking the conditon of the MAP sensor harness connector. In my experience, they dry out and start to crumble, resulting in erratic MAP readings.

 

Thank You for the informative reply to my ongoing problem. When I get a chance(one day this week or weekend) I'll check the wiring. Thanks again for the help that really breaks it down for me. I don't why it ran like a top for 2 days without a miss and now all of a sudden it's problem after problem. Thanks again for all the very helpful information.