electrical help needed bad.


First thing, I'm a newbie corvette owner. I just purchased a 1991 coupe.

Ok, here we go.

i've searched a lot on this topic, so before getting flamed, yes, I have looked.

I checked my codes on this car, using the ALDL with a short jumper wire. I tried to use my scan tool, but there was no connection/communication.???wtf

anyway, I jumpered terminal "G", and on the display, I got this.

1

C41......Electronic Spart Timing (ESC) circuit
H41......Same
H54 .....low voltage to fuel pump

4.

ERR

1.0

That's exactly how it flashes up on my speedo.

Car is running like crap. I've purchase everything to flash my chip,and have with a stock bin, and still have the same problem. Swaped ECM housings, with the same problem.

I took a spark test light, and put it on #1 spark plug wire, and you can see that there is a definite miss. I put it on another spark plug wire, and it was worse.

The TACH is showing about 2 times the RPM that the engine is actually turning.

Speedometer works when it wants to.

This car had an aftermarket radio in it at one time, bezel had be "clearanced" . Stock one was in it when I bought it. I have it out now, and the wiring harness looks as if it has not been cut or butchered up. It tried to follow it, but it ran down by the tranny tunnel, towards the back. Don't know where it goes, but in the passenger storage compartment, there is a wiring harness (purple, black, red, and yellow), along with a telephone cable looking thing, and coaxal cable there. It has an old school big 'ol phone in the car, so I think that is what this is.

"sys" light flashes when going down the road, which I think that it should with the trouble that I'm having.

Car runs supper rich, but it should since the PCM is thinking that it is running double (tach) that is actually is.

Things that I need: I need a service manual that will actually help me trouble shoot this car, this HAYNES manual is crap. Links please

Where is the CCM? I need to check the wiring into this unit. I saw a writeup where you can check the wiring between the ccm and the PCM. (c5d wrote a good troubleshooting guide on this forum)

Any ideas? I'm checking battery voltage with my meter in a little while.

Thanks

David Moss

 

CCM


The reason that I was searching for the CCM, which I found directly behind the radio, and haven't even attempted to get to it yet, was because I can't get ANY communication through the ALDL port. The data link wire that goes form the ALDL, goes to the CCM and ECM.

When I use a jumper wire in the ALDL ports "A" and "G", the gauge cluster with run through the ECM codes, but it shows ERR on the module 4.


I've replaced the ECM housing with a housing from a Camaro, which had the same GM part number, with my stock mem-cal, and that didn't work. I took my stock memcal, and put it on an adapter from craig moates, burnt my chip with my stock file and another stock file, and that didn't help. My scan-tool (actron) will not communicate at all with the ECM. (Seems with the Camaro mem-cal, it did communicate though, I'll check tonight)


I saw a thread on here on how to check the wiring between the CCM, ECM, and ALDL port, so that's why I was looking for the CCM.

http://www.digitalcorvettes.com/for...p;highlight=ERR

As far as the tach and miss firing, I thought that the CCM may have had something to do with it also, but I guess I was wrong on that one, maybe.

Somewhere, I have an electrical/communication problem, and I just have to find it;

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1. Speedometer works when it wants to

That's why I took the radio out, to make sure the wiring had not been butchered. I know the speed sensor wire goes to the radio, for some reason or another. Found nothing, so I thought that it was in the PCM, so I replaced it, no help.
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2. "sys" light flashes when going down the road, which I think that it should with the trouble that I'm having.


When I tried to get the codes for this, I got an ERR. I heard that with a aftermarket radio, it would throw this code due to the dimming function circuit on the radio being open, but I didn't see any open circuit on the radio, all wires were hooked up. Also, somewhere I saw a CCM communication problem will cause this.

http://www.digitalcorvettes.com/for...p;highlight=ERR
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3. I took a timming light, and put it on #1 spark plug wire, and you can see that there is a definite miss. I put it on another spark plug wire, and it was worse.

The TACH is showing about 2 times the RPM that the engine is actually turning.

3. TS....This would definately fall under a module in the distributor problem, but with all the other funky things going on in this electrical system, I'd hate to replace this if there is nothing wrong with it. I'll have it checked out though. I still think it is in the ECM/CCM communication problems.
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4. Gas gauge wrong

I can fill the car up, and it will still show 1/2 tank one minute, then 2 bars the next minute.

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quote: i would scout around for a tech in your area too that can maybe give some direction it won't hurt.


Around here, I am the one people come 2. This one is kicking my tail end though. My first vette, and the first one I've ever worked on too. I'll have it down once that manual gets here.

Thanks everyone, and still looking.

D Moss
(803)360-3975

 

wiring


Alright,

I've pulled the CCM, and checked the wiring on the ALDL serial data circut.

All is well.

And I'm still getting "ERR".

I've seen in my service manual (just got it today, haven't had a chance to really look at it yet), that the serial data wires also run to the heater controls, could this be interfeering with my signal between the ECM and CCM?

I've check continuity between CCM white connector 13 and ECM 11 and getting no resistance between the 2 points. I've checked for resistance between the serial data point on the ALDL port under

________________________________________
__

TROUBLSHOOTING FROM C5D (under search function)

Loss of Communications
The Serial Data Circuit is a master (CCM)/slave (ECM) configuration.

The CCM polls the ECM. If the ECM fails to respond after 3 consecutive polls (3x200ms/600 miliseconds) a Code 41 sets.

The Serial Data Circuit links Serial Data 1 to Serial Data 2, which includes the electronic HVAC controler, ECM, ALDL teminal, and anti-lock braking controller.

Diagnosis:
Jump ALDL TERM "G" and "A"
IGN ON
Press "TRIP RESET" until "4.0" displays in Trip Monitor
Note Speedo, does it say "ERR"?

1. MINE SAID "ERR"

NO
A SHORT will take down the whole link. An OPEN will take down only the device(s) that becomes OPEN circuited.

Possible inop TRIP controller.
Loss of English/Metric TEMP display on C68 HVAC control head.
Loss of "Check Gauges" function.

YES
IGN OFF
DIS red (VIN8) or blue (VINJ/LT5) ECM connector
DIS white CCM CON
CON Digital Volt Meter (DVM) between CCM TERM WC13 (800 TAN) and ECM CON TERM R11/B15 (VIN8/J)
Continuity?

2. I HAD NO RESISTANCE BETWEEN EACH POINT. YES CONTINUITY....

NO
Repair OPEN in CKT 800 to CCM PIN WC13

YES
CON DVM between CCM TERM WD12 (800 TAN) and ECM CON TERM R11/B15 (VIN8/J)
Continuity?

3. I HAD NO RESISTANCE BETWEEN EACH POINT. YES CONTINUITY.....


NO
Repair OPEN in CKT 800 to CCM PIN WD12

YES
CON Digital Volt Meter (DVM) between CCM TERM WC13 (800 TAN) and GND.
Continuity?

4. NO CONTINUITY. I HAD ABOUT A 9.4 V REISITANCE???

YES
Repair SHORT to GND in CKT 800

NO
CON TEST LIGHT between CCM TERM WC13 (800 TAN) and GND.
IGN ON
Test Light ON?

5...........NO TEST LIGHT ON

YES
Repair SHORT to B+ in CKT 800

NO
Repeat test from first "YES", except use use ECM TERM R5 where R11, and B20 where B15, is specified.

I DID, AND EVERYTHING CHECKED OUT!!!


D Moss

 

Thanks

D Moss

 

Alright, I read and looked at a post wrong.

When you ground out terminal "g" with terminal "A" on the ALDL, the CCM is module 1, and the ECM is module 4.

I read it wrong, and thought the ECM was module 1, and the CCM was module 4. I was trying to troubleshoot the wrong problem.

CCM codes:

Code 41= Loss of ECM serial data communications

H41= same, just historical

H54= PASSKEY fuel enable failure



My service book states with a Code 41, go through troubleshooting above, and also check ECM (through ALDL) for code 51, which is the faulty mem-cal code. I'll check this tommorow.

I know, that Code 41 was also in my ECM, and that by my service manual is;

C41= Cylinder select error (faulty or incorrect mem-cal)
5.7L (vin 8) "y" carline (PORT)

On tunercat, under # of cylinders, I have 0. I checked a couple of other bin files that I got offline, and they have the same thing. Can someone check theirs, and see what they have?

I believe that I'm going to need a MEM-CAL.

Thanks

D Moss

 

I put an ECM in the car, and everything straightened out. Mem-cal was bad, and that's even when I was programming the craig moates chip with piggy back connector with a good bin file.

There's more to the MEM-CAL than just the chip that we bypass with the piggy back connector.

D Moss