Diagnostic Aids
WARNING: This page is about a different car, the 2000 Isuzu Hombre. However, it is still accessible from the selected car via links, so may be relevant.
Scan tool should indicate vehicle speed whenever drive wheel is turning at greater than 3 MPH. A DTC P0502 can falsely set if engine is "brake torqued" in gear. Disregard code if set while drive wheel is not turning. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation. Thoroughly check VSS circuits.