SDM - NO COMM message
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Joined: Aug 2017
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From: Rock Hill SC
SDM - NO COMM message
My 98 C5 is posting a message on the DIC that states "SDM-NO COMM" so I guess the SD module is not communicating with the IPC. I recently changed the IPC to new - used one and transferred the odometer chip but have not gotten the original VIN programmed in. A GM Master Tech told me that the VIN mismatch would not cause this problem, it's either a power issue or failure in the COMM link to the IPC. To the best of my knowledge the car has not been crashed and there are no crash issues reported on CARFAX. I checked out the issue in the SM but it does not address this message. I checked for the dumb stuff like blown fuses and disconnected wires under the seat, all is OK there. Has anyone encountered this one before?
Thread Starter
Intermediate
Joined: Aug 2017
Posts: 25
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From: Rock Hill SC
Thanks, trying to figure out how to do that without tearing half the car apart to get to the SDM. Service Manual is not super-clear on location of the connectors outside the console where the SDM lives. I'll continue to study the SM and find a good spot for a power and ground check. Car is rarely driven so I'm not in a rush.
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Joined: Sep 2013
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From: Cape Coral, Florida
Thanks, trying to figure out how to do that without tearing half the car apart to get to the SDM. Service Manual is not super-clear on location of the connectors outside the console where the SDM lives. I'll continue to study the SM and find a good spot for a power and ground check. Car is rarely driven so I'm not in a rush.
Thread Starter
Intermediate
Joined: Aug 2017
Posts: 25
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From: Rock Hill SC
As usual, I just had the trim panels out to replace the IPC. Was hoping I could do this elsewhere, i.e. without taking it apart again, this will be number 4 in the last month (the fault didn't show up till after I replaced the IPC!! I appreciate the advice, at present I have the intake off to replace knock sensors and the knock sensor harness. There are no U codes, only and air bag light and an SDM - NO COMM on the DTC. When the knock sensors are wrapped up I'll pull out the trim and take a shot at it. Like most "things Corvette", you can be sure it will be the most expensive fix possible, e.g. SDM is shot. Thanks for the advice, I appreciate the help from you guys that know these cars much better than I ever will.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,613
Likes: 4,061
From: Cape Coral, Florida
As usual, I just had the trim panels out to replace the IPC. Was hoping I could do this elsewhere, i.e. without taking it apart again, this will be number 4 in the last month (the fault didn't show up till after I replaced the IPC!! I appreciate the advice, at present I have the intake off to replace knock sensors and the knock sensor harness. There are no U codes, only and air bag light and an SDM - NO COMM on the DTC. When the knock sensors are wrapped up I'll pull out the trim and take a shot at it. Like most "things Corvette", you can be sure it will be the most expensive fix possible, e.g. SDM is shot. Thanks for the advice, I appreciate the help from you guys that know these cars much better than I ever will.
Thread Starter
Intermediate
Joined: Aug 2017
Posts: 25
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From: Rock Hill SC
One other question. I can't find out whether the SDM is specific to a VIN; i.e. if the IPC is swapped and the original VIN has not been re-programmed could this cause the module to loose communication? I can't find any info in the service manual about VIN programming issues.
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Thread Starter
Intermediate
Joined: Aug 2017
Posts: 25
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From: Rock Hill SC
FINAL POST - After a lot of fooling around with grounds, power supply and checking connectors with no faults I became convinced the problem was the SDM itself. I found a replacement with the identical part and service number. I installed it and the computer picked it up right away. the light is out and all is well. I really suspected the SDM right out of the bat but was reluctant to change it because of the need to re-program, Found out that the VIN is not in the SDM, What is checked in the state of health test that it does when the car is turned on is to look for the last 4 digits of the part number. If it's the same communication is established. So my problem is fixed without any costly outside "help".
