2001 Ford Mustang

Computer problem
2001 Ford Mustang V8 Two Wheel Drive Manual 73000 miles

I have a 2001 Ford Mustang Cobra that consistently registers 10 MPH faster than actually speed of car. This always occurs after I have surpassed about 25 MPH.

Problem first occured after the car sat for 15 months while I was deployed overseas. The car was turned on very minimally during that 15 months unfortunately. As a result I ended up replacing the battery because it was dead.

Tire/rim size have not changed, nor do they differ from original specs.

The needle does not stick or hesitate at any point.

Can someone please help explain what happened and how to fix it? Thank you so much for your help.
May 20, 2009.

Problem lies in either the sending unit on trans. (VSS) or the gauge itself.

I would replace the sending unit, they are about $30, so it would be a good starting point.

May 20, 2009.
Maybe the Output Shaft Speed Sensor located on left side of trans. Have it hooked up to a scanner then drive compare scanner to car if same then sensor is reading wrong.
Hope this helps
Thanks for donate
If OSSS good the gague faulty.

May 20, 2009.
The VSS and OSSS are completely different sensors, correct? This is a manual tran, do they have both and are they accessible?

May 20, 2009.
The OSS sensor sends a signal to PCM to indicate output shaft speed. It is used for TCC, Shift scheduling and EPC (electronic pressure control).

Depending on model it uses either one for speedometer/odometer control.

Looks like the OSS is Ford only, I cannot find the part at any parts stores.

I would follow Doc's instructions, it will give you a definitive diagnosis.

May 21, 2009.