I have a 04 gt 5 speed, Iv only had the car a few months and have noticed with all my highway driving lately that the speedo is off. It seems to be off by 10-15 mph on the highway, and 5-10 or so in the city. My first thought was it had gears in it but the car drives like a stock car, I havent jacked it up and checked the tire to driveshaft ratio but in all honesty I dont see how it could have gears. Has anyone had a problem with the speedo, I know its all electronic so what could cause this? Any info would be great, im racking up alot of bs mileage because of this.

 

Another possibility is that the speedometer needle has been incorrectly placed. You can use the instrument cluster diagnostic mode (click here) to see what speed the PCM believes your are traveling and determine if the needle is wrongly installed.

Select the "m" mode to see the speed in km/h, to convert to mph multiply km/h by 0.6214.

The speedometers in the '01 to 04 Mustangs are generally quite accurate. You might have "gears", 4.10s would account for the difference you describe.

 

I payed more attention today and it it 10-15 off all around. Thanks for the info ill try that but the thread doesnt work, could you give it to me again.

 

I also noticed the trip odemeter seems to be turning a little faster then it should

 

Any ideas would be good guys

 

I fixed the link in my original posting above, here it is again also...