I've got a 97 Z28, V8 5.7L manual Transmission. I've not been able to get it to pass emissions due to 3 codes I keep getting. The codes are P0100(mass airflow sensor) P0372(crankshaft sensor) and P1657(skip shift solenoid). My thoughts were the MAF was only thing keeping it from passing emissions but I'm not sure. Since I've found what codes were, I've installed new MAF as well as crankshaft sensor. I disconnected battery and even used computer to clear codes but they keep coming back. I can't be the only one with this issues so I'm hoping someone can help me. Thanks again.

 

check the 20 amp fuse in the under hood fuse box, check for bad connectors and broken or damaged wires going to the maf

 

Thanks Craby, I'll give it a go

 

The skip shift solenoid & MAF are on the same fuse, Fuse 10 (Engine Sensor).


PO372 is a "High Resolution" code, It comes from the Opti Spark not the CKP sensor on the bottom of the timing cover, Generally this code indicates a failing Opti Spark.

 

Ok, I've gotten all codes handled except that P0372. I have replaced everything else except the opti spark. I've done it before when my water pumps seal began leaking and know how much of a nightmare it is to get to. You think I should replace opti spark next? :/

 

It could very well be a wiring/connection issue, Unplug the distributor connector & check for corrosion. The one at the Opti, Not the jumper harness on the intake.


The latest GM Opti-Sparks, The jumper harness is sealed at the distributor. Do Not cut the seal off to do the above test. Let me know.


Next step is to examine the vacuum & vent lines to the Opti, If damage is found....Fix it, But the damage may already be done & a new distributor is most likely in your future.


Last & Definitely not least...Circuit Performance Testing.
1. Disconnect the distributor electrical connector.

2. Key On Engine Off (KOEO), test voltage on the Purple/White wire, circuit #430, pin B.

3. Should have 5 V on this wire.

4. Engine running, test this same circuit with a scope.

5. Expect an evenly spaced 0-5 V pulse, 720X, (720 pulses per camshaft revolution).


If you do end up buying a distributor, Buy latest design from GM, They might have finally got it right.


Grounded/Arching plug wires are a death sentence to a Opti-Spark distributor, I never route them around the accessory bracket I go between the block & bracket.

 

Thank you so much clinebarger, I'm going to give this a go tomorrow after work. I'll let you know how it goes. Also researched www.deleteq.com. May do that if I have to replace opti and do away with it all together

 

Wow, I never knew that existed, Thanks. That is absolutely correct, The secondary ignition & voltage plays hell on the optical parts.


A even better set-up is running a LS 0411 PCM & eliminate the opti all together, Info can be found here at EFI Connection EFI Connection, LLC - EFI Connection 24x System

 

opti wire harness is a common fail.