speed problem
Thread Starter
Joined: Mar 2012
Posts: 8
From: South Dakota
speed problem
hey guy just got a 2001 gt and I noticed that my speedometer is off by about 10 mph do you have any suggestions on what I could do to get it fixed or if anyone has had any problems like this before. thanks for your help
4th Gear Member
Joined: Sep 2009
Posts: 1,481
From: NC
Lucky for you, you probably have aftermarket gears in the rear and the speedometer just needs correction. This can be done with a SPEEDCAL module or a handheld tuner(SCT is a good choice).
If you have a GPS, check what your speedometer reads at an actual 60mph and we can easily tell you what gear ratio you have in the car now.
If you have a GPS, check what your speedometer reads at an actual 60mph and we can easily tell you what gear ratio you have in the car now.
Thread Starter
Joined: Mar 2012
Posts: 8
From: South Dakota
alright thanks for the help i have only had this car for a couple weeks and when i bought it i didnt get any more details that the usual form a dealership so im trying to get everything figured out with it
TECH SAVANT
Joined: Dec 2006
Posts: 10,937
From: Saint Augustine, FL
First use the instrument cluster diagnostic mode's enG function (click here) to determine if the digitally displayed speed matches the speedometer. If it does then you will know the speedometer indicator needle is properly placed, obviously if the digital and meter speed do not match (within 1-2 mph) then the indicator is incorrectly placed.
Next check the vehicle speed with a GPS, borrow one if you have to. The civilian GPS is accurate to 0.1 mph. Report back with the GPS results and we can go from there.
Next check the vehicle speed with a GPS, borrow one if you have to. The civilian GPS is accurate to 0.1 mph. Report back with the GPS results and we can go from there.
4th Gear Member
Joined: Sep 2009
Posts: 1,481
From: NC
3.73 gears would make your speedometer read 68.44mph at a true 60mph speed.
My guess is that you have 3.73 gears and just need a handheld tuner to recalibrate the speedometer.
Note: if you have 3.90 gears, your speedometer would read 71.56mph at a true 60mph speed.
What size tires do you have on the rear of the car? A size different than stock will also effect the accuracy of the speedometer.
You may have to check your speedometer in a more accurate manner. Try going an exact speed on your speedometer and then reading the digital speed from your GPS. That should be slightly more accurate than trying to decide exactly how fast your speedometer is reading at an odd speed.
My guess is that you have 3.73 gears and just need a handheld tuner to recalibrate the speedometer.
Note: if you have 3.90 gears, your speedometer would read 71.56mph at a true 60mph speed.
What size tires do you have on the rear of the car? A size different than stock will also effect the accuracy of the speedometer.
You may have to check your speedometer in a more accurate manner. Try going an exact speed on your speedometer and then reading the digital speed from your GPS. That should be slightly more accurate than trying to decide exactly how fast your speedometer is reading at an odd speed.
TECH SAVANT
Joined: Dec 2006
Posts: 10,937
From: Saint Augustine, FL
^+1, it may be the PO had a tune and flashed the PCM back to stock when he sold the car.
You should also do the instrument cluster diagnostic test I linked above, to make 100% sure the speedometer indicator is properly placed.
You should also do the instrument cluster diagnostic test I linked above, to make 100% sure the speedometer indicator is properly placed.
First use the instrument cluster diagnostic mode's enG function