Querying CCM Through ALDL?
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Instructor
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From: New Jersey
Querying CCM Through ALDL?
All,
A few weeks back I purchased a 1990 Base L98 Coupe with a mileage discrepancy. Previous titles show more than 100k miles, but dash readout is showing 41k. I know that this info is stored in the CCM and so EITHER the car only has the 41k miles indicated (and there was a mistake during a previous title transfer) OR the car has some indeterminate number of miles. Just by way of wanting to know, I'd like to find out if the CCM in the car seems to be the original. I understand that the VIN and mileage, options, etc. are programmed into the CCM when it's replaced (with the exception that the mileage of a used one wouldn't be able to be changed).
I bought a Moates ALDL cable assembly and have successfully used it to connect to the ECM and datalog, but I cannot find anything online about querying information out of the CCM. I believe this was possible with the old Tech1 scanners over the same port, so I'm figuring it must be possible for the adapter as well. If anyone has any experience reading out information from the CCM, a point in the right direction would be much appreciated. Thanks in advance.
A few weeks back I purchased a 1990 Base L98 Coupe with a mileage discrepancy. Previous titles show more than 100k miles, but dash readout is showing 41k. I know that this info is stored in the CCM and so EITHER the car only has the 41k miles indicated (and there was a mistake during a previous title transfer) OR the car has some indeterminate number of miles. Just by way of wanting to know, I'd like to find out if the CCM in the car seems to be the original. I understand that the VIN and mileage, options, etc. are programmed into the CCM when it's replaced (with the exception that the mileage of a used one wouldn't be able to be changed).
I bought a Moates ALDL cable assembly and have successfully used it to connect to the ECM and datalog, but I cannot find anything online about querying information out of the CCM. I believe this was possible with the old Tech1 scanners over the same port, so I'm figuring it must be possible for the adapter as well. If anyone has any experience reading out information from the CCM, a point in the right direction would be much appreciated. Thanks in advance.
Thread Starter
Instructor
Joined: Jul 2020
Posts: 227
Likes: 43
From: New Jersey
No. The VIN and options are NOT programmed into the CCM in a 1990. You can take a used one (from a 1990, each year is a different P/N and has different pin-outs and programming), plug it in, change the key/VATS resistance and it will operate correctly. The odometer reading will be what accrued in the previous car.
There is nothing in the 90, 91, or 95 FSM about programming VINs or options into replacement CCMs. Only the odometer reading prior to 100 miles, and learning key resistance for VATS on a new module.
Unless there is a credible paper history with the car or condition supports the 'low' mileage, it is not unreasonable to expect a 30 year old car to have in excess of 100k on it. That's only 3,333 miles a year average. It probably had 30,000 after the first two years.
The CCM is fussy to access, but the only clue to a replacement or used ECM will be by a visual inspection. Look for the production line sticker and broadcast code. ATTJ is correct for 1990. "Service Replacement" will appear on service replacement units. These will have needed to have the odometer reading transferred, but anecdotal evidence suggests it rarely was. Some salvage-car CCMs may have a sticker or writing on them indicating the VATS code. I've never done it, but there are probably date codes on ICs, circuit board, and other internal components if they can be 'cracked'. There's some clues to look for on a replacement CCM.
There is nothing in the 90, 91, or 95 FSM about programming VINs or options into replacement CCMs. Only the odometer reading prior to 100 miles, and learning key resistance for VATS on a new module.
Unless there is a credible paper history with the car or condition supports the 'low' mileage, it is not unreasonable to expect a 30 year old car to have in excess of 100k on it. That's only 3,333 miles a year average. It probably had 30,000 after the first two years.
The CCM is fussy to access, but the only clue to a replacement or used ECM will be by a visual inspection. Look for the production line sticker and broadcast code. ATTJ is correct for 1990. "Service Replacement" will appear on service replacement units. These will have needed to have the odometer reading transferred, but anecdotal evidence suggests it rarely was. Some salvage-car CCMs may have a sticker or writing on them indicating the VATS code. I've never done it, but there are probably date codes on ICs, circuit board, and other internal components if they can be 'cracked'. There's some clues to look for on a replacement CCM.
I assumed that this step with the Tech1 is what would program the various options into the CCM. For example, though I know it would be required within the first 100 miles, I didn't stumble across anything in the FSM that specifically called out programming the mileage into the replacement unit. I do see what you're mentioning about the VATS programming, however.
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An inquiry with a Tech1 or (a) can check VIN. If the VIN doesn't match the VIN of car then it pretty much confirms that the CCM is from a salvage car OR if 'matches' it has been likely tampered with'. There would be no reason to pull it for checking the labels or maybe tire crayon info from JY.
OP - Does the condition of the car hint 100K+ or the 41K displayed? I'd think there should be obvious.
*** There's actually a TSB that references a procedure change for ODOMETER entry for '90. TSB specifically mentions 'after VIN' entry. TSB is 90-373-8C. I have the TSB but can't post it BUT here's a WEBCACHE from CAC
http://webcache.googleusercontent.co...trip=1&vwsrc=0
Last edited by WVZR-1; Jul 31, 2020 at 01:30 PM.
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No. The VIN and options are NOT programmed into the CCM in a 1990. You can take a used one (from a 1990, each year is a different P/N and has different pin-outs and programming), plug it in, change the key/VATS resistance and it will operate correctly. The odometer reading will be what accrued in the previous car.
There is nothing in the 90, 91, or 95 FSM about programming VINs or options into replacement CCMs. Only the odometer reading prior to 100 miles, and learning key resistance for VATS on a new module.
Unless there is a credible paper history with the car or condition supports the 'low' mileage, it is not unreasonable to expect a 30 year old car to have in excess of 100k on it. That's only 3,333 miles a year average. It probably had 30,000 after the first two years.
The CCM is fussy to access, but the only clue to a replacement or used ECM will be by a visual inspection. Look for the production line sticker and broadcast code. ATTJ is correct for 1990. "Service Replacement" will appear on service replacement units. These will have needed to have the odometer reading transferred, but anecdotal evidence suggests it rarely was. Some salvage-car CCMs may have a sticker or writing on them indicating the VATS code. I've never done it, but there are probably date codes on ICs, circuit board, and other internal components if they can be 'cracked'. There's some clues to look for on a replacement CCM.
There is nothing in the 90, 91, or 95 FSM about programming VINs or options into replacement CCMs. Only the odometer reading prior to 100 miles, and learning key resistance for VATS on a new module.
Unless there is a credible paper history with the car or condition supports the 'low' mileage, it is not unreasonable to expect a 30 year old car to have in excess of 100k on it. That's only 3,333 miles a year average. It probably had 30,000 after the first two years.
The CCM is fussy to access, but the only clue to a replacement or used ECM will be by a visual inspection. Look for the production line sticker and broadcast code. ATTJ is correct for 1990. "Service Replacement" will appear on service replacement units. These will have needed to have the odometer reading transferred, but anecdotal evidence suggests it rarely was. Some salvage-car CCMs may have a sticker or writing on them indicating the VATS code. I've never done it, but there are probably date codes on ICs, circuit board, and other internal components if they can be 'cracked'. There's some clues to look for on a replacement CCM.
T o the OP, yes, you can use a Tech 1 to view the VIN that is written to the CCM. That is one way to verify. But you know with mileage that is displaying on the cluster does not match with the history of the vehicle report.
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Instructor
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From: New Jersey
VIN is!!!!!! Options aren't but they are mentioned in the procedure because other GM of that vintage did require options.
An inquiry with a Tech1 or (a) can check VIN. If the VIN doesn't match the VIN of car then it pretty much confirms that the CCM is from a salvage car OR if 'matches' it has been likely tampered with'. There would be no reason to pull it for checking the labels or maybe tire crayon info from JY.
OP - Does the condition of the car hint 100K+ or the 41K displayed? I'd think there should be obvious.
*** There's actually a TSB that references a procedure change for ODOMETER entry for '90. TSB specifically mentions 'after VIN' entry. TSB is 90-373-8C. I have the TSB but can't post it BUT here's a WEBCACHE from CAC
http://webcache.googleusercontent.co...trip=1&vwsrc=0
An inquiry with a Tech1 or (a) can check VIN. If the VIN doesn't match the VIN of car then it pretty much confirms that the CCM is from a salvage car OR if 'matches' it has been likely tampered with'. There would be no reason to pull it for checking the labels or maybe tire crayon info from JY.
OP - Does the condition of the car hint 100K+ or the 41K displayed? I'd think there should be obvious.
*** There's actually a TSB that references a procedure change for ODOMETER entry for '90. TSB specifically mentions 'after VIN' entry. TSB is 90-373-8C. I have the TSB but can't post it BUT here's a WEBCACHE from CAC
http://webcache.googleusercontent.co...trip=1&vwsrc=0
Thanks. That TSB and your understanding more closely matches what I thought was the case. To be honest, my interest in this is maybe more academic than anything. The car is a bit of a mixed-bag as far as indications of mileage. It's clearly got a replacement ECM and so could easily have a replacement CCM. Interior is quite worn - but weatherstripping was shot and between constant water incursion and UV, I could see that beating up the leather just as bad as long-term usage. The usual place I would look for a mileage indication is pedal surface wear - but there's very little on this car that I can see. Aside from this diversion with the CCM, my next plan to see what we're dealing with on the car is a compression test which I'm thinking should tell me a bit about mileage as well.
In any case, what I'm really wondering is how can I query the CCM stuff WITHOUT a Tech 1. My thinking is that if a Tech 1 just communicates via the ALDL, then my Moates cable should allow for it as well. I just wondered if there's software out there that already has the query commands and decoding built into it somehow.
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I read the TSB Dave linked. I used a different cartridge '90-92 EEPROM Service". I can enter the VIN, I can enter the odometer reading. Of course the "upload failed" because the odometer reading is >100.
Allright. I guess VIN is in there. HOW DO YOU PULL IT? Thanks.
Allright. I guess VIN is in there. HOW DO YOU PULL IT? Thanks.
Nice delete. As usual.
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Oh no. I’m talking about the one we’re you were begging us to show you a picture of a 90 with the VIN in a tech 1. And “prove that you were a liar”.
That delete.
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