1999 Jetta Speedometer Reads 10 MPH Slow

[rjfvt]

Hi All,
I bought my daughter a 1999 Jetta and we found a few things wrong with it and I'm hopping someone can help.
1. The speedometer seems to be reading about 8 to 10 miles per hour slower than the car is actually going. What could the problems be?

2. The fuel gage is not working. The needle dosen't move no matter how much fuel is in the tank. What could be the problems?

Thanks for your help.

Rick

[zackforbing]

does the car have wheels that are bigger than 15"? the computer that controls the speedometer is calibrated for 15" wheels...if you go larger or smaller, it throws the calculations off.

I don't know if the gas guage is run by fuses or not, but you might want to check that to make sure.

[rjfvt]

Hi, thanks for posting,
1. We have 15" tires on it but maybe the people that owned it before had larger wheel. Do you know how I can adjust the speedometer computer?

2. I looked for a fuse on the fuel gage but Didn't find any

[boschmann]

You should compare the tire size to that posted on the door jamb sticker. Fuses 11, 15, and 37 provide power to various instrument cluster functions. In order to test whether the problem is the gauge or the sensor you will need to have access to a multimeter to check resistance.

[rjfvt]

On the fuel guage not working, I checked fuses 11, 15, & 37 "All fuses are good." What would be my next step in troubleshooting the Guage problem?

As far as the slow speedometer readings, I checked out the door sticker to see the wheel size and didn't find anything that states the wheel size. I noticed the headlghts are pointed very low and the speedometer is slow. Do these thing seem to indicate they had larger wheels on it before I bought it? Do you thing all I have to do is calibrate the computer???

Thanks,

Rick

[redhawk14506]

Could be, I had a friend who got pulled over for doin 70 in a sixty zone after installing new rims, so it could be the old owners customized the car then replaced the rims with the stock AFTER reprogramming the computer for the bigger rims. Good luck

[boschmann]

I don't know of any way to reprogram the cluster for different rims, most likely you haave slightly different tires than factory. There should be a sticker stating the proper (factory) size. As for the gauge, if you have a multimeter I can help more, but a simpe test would be to go to the tank sender wire harness (through the fuel pump/sender access hole above the tank in trunk). If you connect the violet with black trace wire to ground the gauge should read full (key on). If it does, the sensor is probably bad.

[Igovert500]

VSS, vehicle speed sensor might need to be replaced. I know this is a common problem for Hondas. I don't know about Jettas, but it might be a possible solution.