1993 Corvette - Fluctuating Electronics
Thread Starter
6th Gear
Joined: Apr 2004
Posts: 6
Likes: 0
From: Clear Brook VA
1993 Corvette - Fluctuating Electronics
Currently have a 1993. Don't drive much...used mostly for shows. I've noticed that my fuel electronics fluctuate when I drive. My MPG goes up/down constantly with unusual figures. It can go from 15 to 60 then down. My miles left is the same way. All my electronics are unreliable. I can't even trust how much gas I have...or how many miles left.
I've called a Chevrolet dealership and they can't figure it out. They want to try replacing the Fuel sending unit now. Does this sound feasible to anyone???
Any ideas/recommendations would be greatly appreciated.
Terri Payne----please email responses to tpayne@valleyproteins.com
I've called a Chevrolet dealership and they can't figure it out. They want to try replacing the Fuel sending unit now. Does this sound feasible to anyone???
Any ideas/recommendations would be greatly appreciated.
Terri Payne----please email responses to tpayne@valleyproteins.com
Drifting
Joined: Nov 2002
Posts: 1,593
Likes: 0
From: Mobile AL
St. Jude Donor '05
Re: 1993 Corvette - Fluctuating Electronics (tpayne93)
If, as you state "all my electronics are unreliable" you probably have a grounding problem in the dash somewhere. I would start there.
Le Mans Master
Joined: May 2003
Posts: 5,362
Likes: 3
From: Delray Beach FL
Re: 1993 Corvette - Fluctuating Electronics (tpayne93)
I just had my 93 in the dealership to check the fuel gauge sending unit, since it was not working properly. I was hoping I would have had it replaced because of gas I received from Shell Oil in South Florida, but it turns out it wasn't the problem. The problem stems from the central control module. I think you may have the same problem. Good luck! 
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
Re: 1993 Corvette - Fluctuating Electronics (tpayne93)
a bit of understanding here:
The CCM - Chassis Control Module is the main computer in the car.
The ECM - Engine Control Module is the engine controller. which makes the car run.
The ASR/ABS Computer controls the traction control and anti-lock braking systems.
There is a serial data line that runs between the ECM and the CCM, and another from the ASR/ABS computer to the CCM.
The CCM then takes these data elements and uses them to control everything and pass data between the other modules (speed, temps things like that).
It also sends data to the gauges.
If the CCM fries, things like this can happen.
What you need to do is test the CCM, not the ECM. The CCM can be tested by jumping pins A and G on the ALDL. This will present the operator with codes in an easy to read format, on the speedometer. Really neat, actually.
If you want more info on this, please, let me know. There is an entire diagnostic procedure that will allow the user to scan through codes and reset them. All using the DIC!!!
Way cool.
So cool, I am going to post something about it in C4 Tech... just need to do it... been real busy... moving and such...
The CCM - Chassis Control Module is the main computer in the car.
The ECM - Engine Control Module is the engine controller. which makes the car run.
The ASR/ABS Computer controls the traction control and anti-lock braking systems.
There is a serial data line that runs between the ECM and the CCM, and another from the ASR/ABS computer to the CCM.
The CCM then takes these data elements and uses them to control everything and pass data between the other modules (speed, temps things like that).
It also sends data to the gauges.
If the CCM fries, things like this can happen.
What you need to do is test the CCM, not the ECM. The CCM can be tested by jumping pins A and G on the ALDL. This will present the operator with codes in an easy to read format, on the speedometer. Really neat, actually.
If you want more info on this, please, let me know. There is an entire diagnostic procedure that will allow the user to scan through codes and reset them. All using the DIC!!!
Way cool.
So cool, I am going to post something about it in C4 Tech... just need to do it... been real busy... moving and such...
Safety Car
Joined: Feb 1999
Posts: 3,504
Likes: 4
From: Mexico Beach FL
Re: 1993 Corvette - Fluctuating Electronics (bogus)
a bit of understanding here:
The CCM - Chassis Control Module is the main computer in the car.
The ECM - Engine Control Module is the engine controller. which makes the car run.
The ASR/ABS Computer controls the traction control and anti-lock braking systems.
There is a serial data line that runs between the ECM and the CCM, and another from the ASR/ABS computer to the CCM.
The CCM then takes these data elements and uses them to control everything and pass data between the other modules (speed, temps things like that).
It also sends data to the gauges.
If the CCM fries, things like this can happen.
What you need to do is test the CCM, not the ECM. The CCM can be tested by jumping pins A and G on the ALDL. This will present the operator with codes in an easy to read format, on the speedometer. Really neat, actually.
If you want more info on this, please, let me know. There is an entire diagnostic procedure that will allow the user to scan through codes and reset them. All using the DIC!!!
Way cool.
So cool, I am going to post something about it in C4 Tech... just need to do it... been real busy... moving and such...
The CCM - Chassis Control Module is the main computer in the car.
The ECM - Engine Control Module is the engine controller. which makes the car run.
The ASR/ABS Computer controls the traction control and anti-lock braking systems.
There is a serial data line that runs between the ECM and the CCM, and another from the ASR/ABS computer to the CCM.
The CCM then takes these data elements and uses them to control everything and pass data between the other modules (speed, temps things like that).
It also sends data to the gauges.
If the CCM fries, things like this can happen.
What you need to do is test the CCM, not the ECM. The CCM can be tested by jumping pins A and G on the ALDL. This will present the operator with codes in an easy to read format, on the speedometer. Really neat, actually.
If you want more info on this, please, let me know. There is an entire diagnostic procedure that will allow the user to scan through codes and reset them. All using the DIC!!!
Way cool.
So cool, I am going to post something about it in C4 Tech... just need to do it... been real busy... moving and such...
The only problem I see is: since the CCM has a digital output to drive the segments in the digital dash display and the CCM is flaky, can you rely on what the digital dash is giving you for trouble-codes?
Another alternative is to find someone that has a Vetronix Tech-1A, MasterTech, or Tech-2 scan-tool with the appropriate cartridge to test the CCM. Most GM dealers have one. http://www.vetronix.com/diagnostics/mts3100/index.html http://www.vetronix.com/diagnostics/tech2/index.html
You could also substitute a known good CCM from another vehicle -- even if the option content were not the same (the CCM is programmed for your vehicle and options, ie. C68 climate control, ASR/ABS -- it even has the VIN programmed in it), it should still drive the dash display correctly.
Tom Piper
[Modified by Tom Piper, 12:53 PM 7/6/2004]
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Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
Re: 1993 Corvette - Fluctuating Electronics (Tom Piper)
a bit of understanding here:
The CCM - Chassis Control Module is the main computer in the car.
The ECM - Engine Control Module is the engine controller. which makes the car run.
The ASR/ABS Computer controls the traction control and anti-lock braking systems.
There is a serial data line that runs between the ECM and the CCM, and another from the ASR/ABS computer to the CCM.
The CCM then takes these data elements and uses them to control everything and pass data between the other modules (speed, temps things like that).
It also sends data to the gauges.
If the CCM fries, things like this can happen.
What you need to do is test the CCM, not the ECM. The CCM can be tested by jumping pins A and G on the ALDL. This will present the operator with codes in an easy to read format, on the speedometer. Really neat, actually.
If you want more info on this, please, let me know. There is an entire diagnostic procedure that will allow the user to scan through codes and reset them. All using the DIC!!!
Way cool.
So cool, I am going to post something about it in C4 Tech... just need to do it... been real busy... moving and such...
I agree on this.
The CCM - Chassis Control Module is the main computer in the car.
The ECM - Engine Control Module is the engine controller. which makes the car run.
The ASR/ABS Computer controls the traction control and anti-lock braking systems.
There is a serial data line that runs between the ECM and the CCM, and another from the ASR/ABS computer to the CCM.
The CCM then takes these data elements and uses them to control everything and pass data between the other modules (speed, temps things like that).
It also sends data to the gauges.
If the CCM fries, things like this can happen.
What you need to do is test the CCM, not the ECM. The CCM can be tested by jumping pins A and G on the ALDL. This will present the operator with codes in an easy to read format, on the speedometer. Really neat, actually.
If you want more info on this, please, let me know. There is an entire diagnostic procedure that will allow the user to scan through codes and reset them. All using the DIC!!!
Way cool.
So cool, I am going to post something about it in C4 Tech... just need to do it... been real busy... moving and such...
I agree on this.
The only problem I see is: since the CCM has a digital output to drive the segments in the digital dash display and the CCM is flaky, can you rely on what the digital dash is giving you for trouble-codes?
Another alternative is to find someone that has a Vetronix Tech-1A, MasterTech, or Tech-2 scan-tool with the appropriate cartridge to test the CCM. Most GM dealers have one. http://www.vetronix.com/diagnostics/mts3100/index.html http://www.vetronix.com/diagnostics/tech2/index.html
You could also substitute a known good CCM from another vehicle -- even if the option content were not the same (the CCM is programmed for your vehicle and options, ie. C68 climate control, ASR/ABS -- it even has the VIN programmed in it), it should still drive the dash display correctly.
Tom Piper
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
Re: 1993 Corvette - Fluctuating Electronics (tpayne93)
Would love to have more info. on this.....Please send to tpayne@valleyproteins.com
Thanks!
Terri
Thanks!
Terri
