chopperclay

This problem started with the car not wanting to start when the engine was hot. It started fine when cold and would run fine once started. It just would be difficult to restart once the engine warmed up. I replaced the Opti (Petris unit), at this point the car started and ran fine but again would not restart when warm-Same old story. I then replaced the Coil and no start at all, then ICM, still no start at all. The Codes are 41 and 72. Code 41 indicates an open in the ignition circuit but I'm not sure what I should do next.... Anyone have any suggestions?

toptechx6

Many people believe that a fault code is telling them to replace a part of some sort and auto parts stores perpetuate the myth as a marketing strategy.

Note that they wiil not accept return of electrical parts when they do not fix the problem even if their code scan suggested replacement.

Fault codes indicate a problem in a particular electrical circuit and are only a starting point for real diagnosis. The correct procedure is to follow the step by step troubleshooting fault tree in the Factory Service Manual for the specific fault code . When multiple codes are in memory good practice is to start with the lowest numbered code first. True diagnosis will require additional testing using a digital volt ohm meter or other basic diagnostic tools to isolate the problem in the circuit.
Ignore this crucial step at your own peril, cost of non returnable replacement parts will almost always exceed the cost of the FSM and a few simple tools. Many fault codes are caused by bad wiring or poor connections and require no hard parts at all. Hope that helps.

desertmike1

Code 41 is in your ICM circuit.. check out this video @14:45 then refer to your FSM for a code 41 trouble shoot.

http://www.youtube.com/watch?v=lFCja...ature=youtu.be

chopperclay

Makes good sense. My FSM was the Preliminary FSM that came out in 1993 and the engine and trans. sections were left out. It simply says refer to 1992 FSM. I will get the meter out and see if I can make some sense out of the electrical diagrams and check. Thanks for taking the time to respond. I will check out that video shortly and many thanks TopTech6 Desert Mike.

chopperclay

Car started this am but runs rough for a few seconds and dies, Code 16 appears. I believe this to be low resolution pulse. Now unsure of what to do next. I do have the FSM troubleshooting chart but really unsure of what to do or check to solve the problem...

don hall

Read through this 2012 thread may help:

http://forums.corvetteforum.com/c4-t...mediately.html

chopperclay

Update: Had it running , idled for about 5 minutes but was somewhat rough, now getting Code C41, and the following H31,33,35,37....

scotth48

While checking wires, make sure ground wires are free of corrosion, especially if you have replaced the ICM and coil. Clean and use of dielectric great on connections will help also. As mentioned the FSM is a must for Corvette owners.

chopperclay

Good idea Scott, I'll try this am! Thanks!

chopperclay

On reassembly, I had put the ground back in the wrong spot/ and placed on the upper bolts which are going into the heads instead of the lower bolt that goes into the engine block. I'm thinking and hoping this could have been the problem. I'm going back together with it now but can see that this was likely the problem. Hoping anyway! Thanks Scott!

chopperclay

The ground must attach to the mounting plate which in turn grounds to the lower bolt going in the block????? Anyone know?

chopperclay

It has to, the lead is too short to reach to the block directly.

chopperclay

Cleared the 41 DTC, started up and ran smooth for 5 minutes, I thought I had it licked. Then died. would not restart. got it back on the charger. Stumped again. Still getting the 41 DTC....

pcolt94

I'm thinking this is starting to sound like a ECM problem.
Some people have put a big bag of ice on the ECM to keep it cooler. This may give you an indication if the ECM is causing these problems. If the car starts with the ice on it that might give you a clue.

toptechx6

You may be right Paul, but I haven't heard the OP indicate he has checked the wiring associated with his code 41 except for the ground connection. I would definitely check that before trying an ECM.

chopperclay

I have the DTC 41 troubleshooting diagram and will work my way down it. I unplugged the ICM and have voltage, maybe too much- meter was flickering up and down making a good reading tough. I have a friend coming over today who may can help with this... Onward through the fog!

toptechx6

Good practice to have a helper when checking wiring. One other step I suggest when help is available is to have one person take the reading with the multimeter while the other wiggles the harness between components, this can help locate poor connections or corroded wiring that might otherwise check okay when working alone.
Such false readings can cause you to replace good parts only to have the problem reoccur when the wiring flexes during operation.

chopperclay

Good point. One thing I have done with all the electrical connectors (all the ones I can get access to) is to apply Stabilant 22A. It will certainly help having my buddy over to check the wiring. He probably has a better meter than my Chinese Harbor Freight Special as well. Ill make sure he brings it. Thanks for the excellent tip on checking the harness- we'll see what we can discover

chopperclay

I have been following the DTC 41 troubleshooting chart and have discovered I have a short to Voltage. My next guess it to swap out the Coil and go back with the original coil I previously removed. Any thoughts or advice?

toptechx6

If you are talking about circuit 423 being shorted to voltage why would you think it was a coil problem? The wire should run from the ICM to connector A at the ECM. Did you disconnect ECM connector A when you tested for voltage?