Snap-on or the Vette, which computer lying
Thread Starter
Cruising
Joined: Jun 2007
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Snap-on or the Vette, which computer lying
I have been tracking down some driveability issues and before I go further I need to get my facts straight. The scanner is a snap-on MTG-2500, this is the little brick but with graphing capibilities. The Vette is a 93 LT1.
One issue is the computer tells me I am in P-N when in R-D-L and vice versa. I did a electrical test and determined that I have ground at terminal A (correct) but when shorted to B (supply ground) it indicates that I am opposite P-N vs R-D-L. I also checked the switch and it is preforming properly. Is the computer confused or the ECM messed up?
Second issue is the RPM on the tach are different that the scanner shows. Example the tach says 2000 RPM and the computer shows 2400.
I noticed this while diagnosing a driveability issue and don't need to go further if this is a problem. I did reomve the switch and force the scanner to show R-D-L while driving and did not notice any difference in driveability (strange).
Thanks for any help
Mike
One issue is the computer tells me I am in P-N when in R-D-L and vice versa. I did a electrical test and determined that I have ground at terminal A (correct) but when shorted to B (supply ground) it indicates that I am opposite P-N vs R-D-L. I also checked the switch and it is preforming properly. Is the computer confused or the ECM messed up?
Second issue is the RPM on the tach are different that the scanner shows. Example the tach says 2000 RPM and the computer shows 2400.
I noticed this while diagnosing a driveability issue and don't need to go further if this is a problem. I did reomve the switch and force the scanner to show R-D-L while driving and did not notice any difference in driveability (strange).
Thanks for any help
Mike
Thread Starter
Cruising
Joined: Jun 2007
Posts: 12
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Will get 3rd opinion
never had a problem before and I have scanned many cars. I am wondering if the program would just be messed up for my year vette. The thing is the transmission position sensor (neutral safty) is just signal or no signal so if someone got the specs backwards when designing the program it would do exactly what it is doing. I am going to try to sweet talk one of the local shops to plug in to it just to see the trans position and the RPM to get a third opinion and hopefully find out who is lying.
Thread Starter
Cruising
Joined: Jun 2007
Posts: 12
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thats the thing I don't mind if my tach is off a little as long as the ECM knows what is going on. I am working on a driveability issue so I would like to rule out that being related to my drive problem. If anyone has any experience with the tach reading being off and what effects it had that would be good info for me. Also any one who has experienced this p-r-n-d-l being backwards that would be great also.
Thanks Mike
Thanks Mike
Thread Starter
Cruising
Joined: Jun 2007
Posts: 12
Likes: 0
Scanned it with a Genisis I think from OMC and it came up with park neutral ON when in park and neutral and Off when in gear which I figure sounds right. Also the RPM were less than 100 different, hardly less than what I could call different. So I guess that is not the root of my driveability.
