First off, I want to thank everyone for getting me to this point. I have a 1990 Convertible L98 6 speed. I have no crank. I took the car to the local Chevy Dealership with no luck, so I brought the car home to do the repairs myself. The first thing I did was to verify the integrity of switches etc. I get the same reading on my OHM meter from my ignition key and the end of the ignition cylinder wire where it plugs into the harness, so nothing wrong with the ignition cylinder and wire pigtail. I checked the clutch switch and it is good. Next, I ran diagnostic codes and got, C41, H41, C51, and H51. I expected code 51 because the previous owner replaced the CCM with a used one from a wrecking yard without knowing the resistance value. What is my next step in methodically trying to figure this out? Thanks again.

 

How did a Chevy Dealer not know what's wrong with your vette?

I just had my starter replaced becaue it was seized and wouldn't crank either. Might be worth checking out?

 

They would have eventually figured it out and fixed the problem, however, they had the car for three and a half work days and only put an hour into it. They no longer have a Tech1 diagnostic tool and said the ECM and CCM are not communicating. They had no recommendations and just wanted to keep playing with it, so I brought it home. I didn't want to put a lot of money into a mechanic playing with it.

 

I put the original ECM back in and got the same codes. When I put the original CCM back in, I can't get codes because the speedometer portion of the instrument panel does not display, so I must use the used CCM that the PO put in.. Oh, and another thing, in module 4, it displays "err".

 

Guess I'm just lucky! My mechanic at the local Chevorlet Dealership has a C4 of his own, so he knows them very well! My service advisor is awesome and she treats me like royalty! Hell the last time I had a collapsed pcv hose and oil shooting out the dipstick, they fixed it for free!

 

The best dealership story I've seen since I've been on the forum.

Uncle P I wish I had some help for you but your issue is over my head. I'll be following along because this is a area I need to know more about.

 

Yeah, the problem is, the previous owner just went helter skelter and started tearing everything apart and it must be this or it must be that, replacing this and that, and not running the diagnostics and doing a methodical approach. I have to say I am having a blast with it and when I get it going, it will be very satisfying. I am going through the wiring harness step by step. I put a remote starter on the solenoid and it cranks over beautifully but either the pump is not coming on or the injectors are not getting the signal. At any rate, no fuel. It does fire when I squirt gas in the throttle body. Thanks for the interest, I will keep everyone up to date on my progress.

 

If you sort the VATS resistance the CCM will signal the ECM to energize fuel enable aspect of the ECM. I know you mentioned that the PO said he had it removed but by who? A "novice"? I asked that earlier in the thread and to check the PROM for ID codes etc and don't recall seeing any response. It's good that you got it home and are enjoying the diagnostics. In your particular case it's a lot to overcome!

Ask the PO to tell you more about the person who thought that he eliminated the VATS by programing the PROM. Who was that guy? The culprit likely!

I mentioned a work key cut to rotate the ignition and then supplying the VATS resistance to the harness at the column base. Call a lock smith and see if they'll "rent" their interrogator? You understand what your doing and the conversation may be enough to convince a knowledgeable shop. There's not much demand for the interrogators these days maybe he'll sell it for less than a service call!

 

As I previously mentioned
http://forums.corvetteforum.com/1584133547-post20.html
DTC 41 ;
the nasty Comms fault where the ECM does not talk to the CCM on the serial data link so subsequently no fuel enable signal passed to the ECM
despite the key being read correctly and the CCM functioning correctly
A time consuming, frustrating problem to troubleshoot and solve. Many have tried and failed to achieve a solution ( a working VATS delete chip looks a good option )

You might try
http://www.digitalcorvettes.com/foru...5&postcount=17
http://forums.corvetteforum.com/1554993058-post25.html
http://forums.corvetteforum.com/1555985163-post33.html
http://forums.corvetteforum.com/1574977144-post3.html

Some "light " bed time reading
http://forums.corvetteforum.com/1554492041-post15.html
http://forums.corvetteforum.com/c4-s...cm-or-ccm.html
http://forums.corvetteforum.com/c4-t...wes-is-me.html
http://forums.corvetteforum.com/c4-t...post1574977144

 

I have crank now but no power back at the tank to the fuel pump. I found a faulty clutch start switch. To achieve crank I jumped the start enable relay and jumped the clutch start switch. Right now it is temporary, just trouble shooting. WVZR-1, the PO stopped by yesterday to check on my progress so I asked him about the prom chip, he pointed out the one that supposedly has the VATS delete but said it was five years ago and he doesn't remember the name of the outfit he bought it from, just that he was very disappointed when he put it in and it didn't work. My battle plan is to methodically go through the wiring harness checking for continuity, shorts, bad grounds, etc. Trying not to be impatient because I would really like to replace the ECM, CCM, and VATS delete prom chip and see what happens. My problem with the CCM replacement is I don't know anyone with a Tech1. I am pretty sure I want to do a total VATS delete, it seems to cause a lot of problems to a lot of C4 owners. I don't mind throwing a little money at the car since I got such a good deal on it. You guys have given me some good stuff to work on, thanks.

 

What is a good VATS delete prom chip, about how much and where?

 

Do you have 2 PROMs?

 

Yes, the one from the original ECM and the one with the VATS delete the PO bought to put into the new ECM.

 

I just don't know the integrity of the used CCM the PO bought from a wrecking yard in California. I don't know how to tell if it is working properly. I do know the one he replaced is bad, I get very little display when I plug it in. He bought the ECM new from NAPA five years ago and the new VATS delete chip for it. Again, I don't know for sure if it is working properly. Which wire or wires connect the CCM to the ECM harness and when should they be hot, because it appears the ECM is not getting communication from the CCM?

 

Put it together with the OE/GM PROM, the used CCM and the ECM that you have. You've only one of those?

Your original PROM should likely show ARFP in the window w/16137184.

I haven't used the DIC diagnostics much at all and not in 4 or so years but regardless of codes in module 1.2.06 it should display AD counts, does it? What is it?

 

I have the ECM the PO bought new at NAPA and the original ECM that the PO removed from the car. On the old chip there is a round hole at each end of the chip, in one end it says "DELCO R665", and at the other end is "3R9250". There is a sticker on the back of the chip that says "DELCO ARFP 7185". The old ECM is not OE, it is remanufactured original equipment and on the front of it, it says "number 7-7727, DC Code 0306NH". I ran a couple tests, first, I squirted gas into the throttle body while cranking and it fired up, second, I put 12 volts to the fuel pump at the rear of the car and the fuel pump came on but the car would not start. So, I assume from that, that the injectors are not firing or I am not getting fuel to the injectors. When you say DIC diagnostics, are you talking about the codes that come up on the speedometer?

 

Did you read any of the DTC 41 links I posted for you above ???
Like this one
http://www.digitalcorvettes.com/foru...5&postcount=17
or this one
http://forums.corvetteforum.com/1554492041-post15.html


If you read the links I posted you will see the serial data connection you are missing does not have 12 Volts on it ;
it is a DATA line like a fax or internet line ,in which the passing data is easily interrupted by a bad connection