90 c4 electrical problems
Thread Starter
Intermediate
Joined: Dec 2004
Posts: 46
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From: BLYTHEWOOD S.C.
90 c4 electrical problems
All started when altenator went out. After replacing altenator, no start. (no power to starter enable relay or fuel enable relay or injector pulse.)
1. By-passed starter relay.
2. Fuel pressure 45 psi.
3. 16 ohms on all injectors.
4. Sparkplugs are firing.
I have no LCD power or injector pulse. Should I replace CCM first or ECM? Without LCD, I can't get any codes.
1. By-passed starter relay.
2. Fuel pressure 45 psi.
3. 16 ohms on all injectors.
4. Sparkplugs are firing.
I have no LCD power or injector pulse. Should I replace CCM first or ECM? Without LCD, I can't get any codes.
Last edited by sneaky pete; May 25, 2007 at 08:51 PM. Reason: it seems to me that the ccm is nothing more than a switch for relays & ecm to receive there ground signal.
Melting Slicks
Joined: Dec 2004
Posts: 3,284
Likes: 51
From: Jacksonville, FL
St. Jude Donor '08 thru '26
Just a thought from a new C4 owner. If you know any where you can borrow a scanner, hook it up and run the KOEO protocol and see what the scanner displays.
Short of that the only other thing I can think of is if you know anyone with a spare ECM for your yr see if swapping it makes a difference.
Sorry I don't have anything else to offer up. Good luck with this one, it sounds to be a real hump!
Tom
I should pay closer attention when I read things, sorry! You know for sure the VATS sys is okay....it cuts off the signal to the pump I believe. Do a search on VATS by-pass. Also sounds like you may have a data transmission issue between the CCM and the ECM. Check the FSM. Grounds are all okay? and the fuseable links? I have a 90, LT5 but I think the P/N's for the ECM's are the same...just the EPEOM's are different...not exactly sure...anyway even a 91 ECM with your EPROM in it will run a 90 system.
Short of that the only other thing I can think of is if you know anyone with a spare ECM for your yr see if swapping it makes a difference.
Sorry I don't have anything else to offer up. Good luck with this one, it sounds to be a real hump!
Tom
I should pay closer attention when I read things, sorry! You know for sure the VATS sys is okay....it cuts off the signal to the pump I believe. Do a search on VATS by-pass. Also sounds like you may have a data transmission issue between the CCM and the ECM. Check the FSM. Grounds are all okay? and the fuseable links? I have a 90, LT5 but I think the P/N's for the ECM's are the same...just the EPEOM's are different...not exactly sure...anyway even a 91 ECM with your EPROM in it will run a 90 system.
Last edited by tomtom72; May 26, 2007 at 08:17 AM.
Thread Starter
Intermediate
Joined: Dec 2004
Posts: 46
Likes: 0
From: BLYTHEWOOD S.C.
vats or ccm
Just a thought from a new C4 owner. If you know any where you can borrow a scanner, hook it up and run the KOEO protocol and see what the scanner displays.
Short of that the only other thing I can think of is if you know anyone with a spare ECM for your yr see if swapping it makes a difference.
Sorry I don't have anything else to offer up. Good luck with this one, it sounds to be a real hump!
Tom
I should pay closer attention when I read things, sorry! You know for sure the VATS sys is okay....it cuts off the signal to the pump I believe. Do a search on VATS by-pass. Also sounds like you may have a data transmission issue between the CCM and the ECM. Check the FSM. Grounds are all okay? and the fuseable links? I have a 90, LT5 but I think the P/N's for the ECM's are the same...just the EPEOM's are different...not exactly sure...anyway even a 91 ECM with your EPROM in it will run a 90 system.
Short of that the only other thing I can think of is if you know anyone with a spare ECM for your yr see if swapping it makes a difference.
Sorry I don't have anything else to offer up. Good luck with this one, it sounds to be a real hump!
Tom
I should pay closer attention when I read things, sorry! You know for sure the VATS sys is okay....it cuts off the signal to the pump I believe. Do a search on VATS by-pass. Also sounds like you may have a data transmission issue between the CCM and the ECM. Check the FSM. Grounds are all okay? and the fuseable links? I have a 90, LT5 but I think the P/N's for the ECM's are the same...just the EPEOM's are different...not exactly sure...anyway even a 91 ECM with your EPROM in it will run a 90 system.
Melting Slicks
Joined: Dec 2004
Posts: 3,284
Likes: 51
From: Jacksonville, FL
St. Jude Donor '08 thru '26
Pete this is all I know about ECM's.....sorry it ain't much!:o
I thought needed one for my 90 and the 90 p/n was nla. I was told by the guys that "get" this 'puter stuff that a 91 p/n will work in a 90. The only thing I had to do was change the EPROM, the ECM comes without one anyway. So I took my EPROM out of the OE ECM and used it in the "new" 91 ECM and everything worked.
As a last resort I would suggest calling up Gordon K. The reason I say that is that you sound like you know this stuff and Gordon can help a person that "gets" this stuff.....a guy like me wouldn't understand what he was saying to me because I don't get this stuff.
Tom
I thought needed one for my 90 and the 90 p/n was nla. I was told by the guys that "get" this 'puter stuff that a 91 p/n will work in a 90. The only thing I had to do was change the EPROM, the ECM comes without one anyway. So I took my EPROM out of the OE ECM and used it in the "new" 91 ECM and everything worked.
As a last resort I would suggest calling up Gordon K. The reason I say that is that you sound like you know this stuff and Gordon can help a person that "gets" this stuff.....a guy like me wouldn't understand what he was saying to me because I don't get this stuff.
Tom
Thread Starter
Intermediate
Joined: Dec 2004
Posts: 46
Likes: 0
From: BLYTHEWOOD S.C.
Ecm Replaced
THANKS TOM.HOW DO I GET IN TOUCH WITH GORDON K? I JUST PICKED UP REM. ECM ,INSTALLED MY PROM AND STILL THE SAME THING.
ITS GOT TO BE VATS (CCM).JUST ABOUT READY TO PULL INJECTION ,COMPUTER,DIST OFF AND GO BACK TO OLD SCHOOL(CARB,HEI, ALUM INTAKE) FORGET THIS ELECTRONIC HEADACHE STUFF!!!
NOT MUCH RE-SALE VALUE BUT VERY DEPENDABLE.
ITS GOT TO BE VATS (CCM).JUST ABOUT READY TO PULL INJECTION ,COMPUTER,DIST OFF AND GO BACK TO OLD SCHOOL(CARB,HEI, ALUM INTAKE) FORGET THIS ELECTRONIC HEADACHE STUFF!!! NOT MUCH RE-SALE VALUE BUT VERY DEPENDABLE.
Melting Slicks
Joined: Dec 2004
Posts: 3,284
Likes: 51
From: Jacksonville, FL
St. Jude Donor '08 thru '26
Sorry Pete,
Gordon Killabrew has a web site foryourcar.com. The tech line phone number is listed but it's not free. I don't know what the costs are....I'm too late to the table with this EEC stuff....so I don't even know enough to ask intelligent Q's and I'm sure I would not understand the info given to me!:o
The last vette was a 72 and now this one is a 90....I got a bunch of education to go thru before I can get my head around this stuff!
Tom
Gordon Killabrew has a web site foryourcar.com. The tech line phone number is listed but it's not free. I don't know what the costs are....I'm too late to the table with this EEC stuff....so I don't even know enough to ask intelligent Q's and I'm sure I would not understand the info given to me!:o
The last vette was a 72 and now this one is a 90....I got a bunch of education to go thru before I can get my head around this stuff!
Tom
Instructor
Joined: Mar 2006
Posts: 127
Likes: 0
From: Stockbridge GA
If you want to check the most likely VATs issue, pull your steering wheel and the guts till you get to the ignition switch. There are 2 wires there for the VATs. Most likely one of those is broken.
My roommate is a locksmith and sees this all the time on the VATs cars. When mine broke, he took my key and read the frequency on it. Then he used his machine to "bypass" the VATs to confirm that the signal was not getting by. When it cranks, you know what the problem is.
Call a locksmith. They will probably test it for free or not too much $$. It should run you about $125 if you pay them to change the ignition switch. You do it, $20 for a new switch. $50 for the beer to offset the hassle of changing the switch.
My roommate is a locksmith and sees this all the time on the VATs cars. When mine broke, he took my key and read the frequency on it. Then he used his machine to "bypass" the VATs to confirm that the signal was not getting by. When it cranks, you know what the problem is.
Call a locksmith. They will probably test it for free or not too much $$. It should run you about $125 if you pay them to change the ignition switch. You do it, $20 for a new switch. $50 for the beer to offset the hassle of changing the switch.
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Thread Starter
Intermediate
Joined: Dec 2004
Posts: 46
Likes: 0
From: BLYTHEWOOD S.C.
Ign.switch
ALREADY BYPASSED IT WITH SAME OHMS RESISTOR AS KEY??STARTER RELAY STILL WANT GET GROUND SIGNAL SO I BYPASSED IT. NOW ENGINE AND STARTER TURN BUT STILL NO INJECTOR PULSE. ALL INJECTORS OHM GOOD(16 OHMS). NO GROUND SIGNAL FROM CCM TO MAKE LCD WORK, COURTESY LIGHTS DONT WORK WIN DOORS OPENED. ??????????????? THANKS ANYWAY
THANKS ANYWAY
