When a CNG Car is Worth Less Than The Tank, What do You Do?

Michael Mobile Technician Clinton, Utah Posted   Latest  
Case Study
Programming
2001 Chevrolet Cavalier 2.2L (4) 4-spd (4T40-E)

I was called to a shop that had a 2001 Chevrolet Cavalier that would not pass emission testing due to the Check Engine lamp being on. The code referred to the CNG system. The customer explained that the tank had expired and the cost of the CNG tank would exceed the worth of the vehicle. The tank and associated parts were removed. He wanted to see if the vehicle could be programmed as a gasoline only vehicle and no longer be CNG.

diag​.​net/file/f3jhh8lww…

I thought about this for a little while and came up with a scheme I thought would work. I first needed a non-CNG VIN to work with. I went to Car-Part​.​com looked up the engine computer and found a listing that had a VIN attached. I then left the key off during the ID process in the TIS software. I programmed the PCM as a non-CNG vehicle. I then had to change the VIN. This was done with EFI Live in the scan tool selection. I cleared the codes and started the vehicle. No Check Engine lamp and the engine ran good. I rechecked the VIN and it was good to go.

diag​.​net/file/f1r6xi0n9…

Sometimes we have to be creative in our efforts. The official fix for this vehicle would be to buy a new tank, change the CNG filter and replace any suspect CNG parts. The end user purchased this vehicle because it was something they could afford. The vehicle was saved from the crusher by reverting the vehicle back to gasoline only operation.

diag​.​net/file/f6g9uui5u…

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Mike: I'm confused. From what I think that I know, that tank should've had a 20-year certification. Previous to 1998, it would've been 15 years. Why the discrepancy? Was this vehicle built with an old tank? Guido

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Michael Mobile Technician
Clinton, Utah
Michael Default
 

Guido, I have no idea. Maybe something was discovered at inspection. All I know is that the customer no longer wanted the system.

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Kevin Manager
Leesburg, Virginia
Kevin Default
 

Hi Guido, the CNG Cavalier vehicles used a 15-year certified from the date of manufacture tank. I had to dust off the memory banks since I have not worked on these vehicles in quite some time. I looked in service information and it confirmed the 15 year certification. GM only up-fit the 2000 and 2001 MY Cavaliers with this system. To my knowledge, GM did not use anything longer than a 15-year…

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Kevin: Thanks for the feedback. While it appears that they could've used tank with a 20-year certification, they elected to go with a 15-year certification, for whatever reason. Guido

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

"This was done with EFI Live in the scan tool selection" Can you tell us more about EFI Live ? There are a ton of cars out here not worth the cost of repairs, but people wouldn't be driving the POS if they could afford something nicer. Gotta fix 'em, if you can; great job!

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Michael Mobile Technician
Clinton, Utah
Michael Default
   

Hi Geoff, EFI Live is designed to do custom tuning on GM cars. If you go the custom tuning route, you pay for tokens that allow you to change parameters in the vehicle. Injector size, WOT fueling, Ign Timing, Cam Timing, EGR operation, Immo. I don't use that part of it currently. The diagnostic software has a cool feature that allows you to change the VIN. The idea being you have one ECU for…

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Very cool. Great Info!! Thanks, Mike

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Alejandro Technician
San Diego, California
Alejandro Default
 

Nice, good to know thank you.

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Dwayne Owner/Technician
Myerstown, Pennsylvania
Dwayne Default
 

Interesting fix. The one think I wouldn't like for us in PA is that upon doing the emissions test it would flag us that the VIN has a discrepancy with the registration. But we are able to bypass that. I did hear of inspectors getting questioned about instances of passing cars with VIN mismatches but we have never been called on the carpet about it.

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Alvaro Service Manager
Oranjestad, Aruba
Alvaro Default
 

He was able to reset the original VIN to the same computer on the car. remained as original as it can be. Remove the CNG stuff and nobody will know. :-)

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Dwayne Owner/Technician
Myerstown, Pennsylvania
Dwayne Default
 

OK, thanks for the clarification. I didn't read it close enough.

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Michael Mobile Technician
Clinton, Utah
Michael Default
 

Hi Dwayne, EFI Live was used to correct the VIN back to the vehicle. So the emissions test and scan tools properly identify the vehicle. -Mike

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default
 

Nice thinking outside the box. What's going to happen when one of those flash everything that moves whether it needs it or not shop, just another wallet flush shop, decides there's an update that needs to be performed? All your ingenuity down the drain. Too bad there isn't a way to lock a module with an encrypted password.

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Michael Mobile Technician
Clinton, Utah
Michael Default
 

Hi Eric, I would expect that the vehicle may not last long enough to get there. That would definitely present an "Ever Since" moment. EFI Live will lock the ECU but I don't think that they want to spend another $100 for a token to do that. -Mike

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Chris Technical Support Specialist
Commack, New York
Chris Default
 

On the Ford vehicles that were converted they would cut the FEPS wire and leave a disconnected bullet connector a few inches from the DLC. This was standard practice on that company's conversions. Until the FEPS wire would be reconnected, one would not be able to Flash a PCM.

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