Vehicle Speed Sensor (VSS)

Disconnect 6-pin connector at amplifier. On Continental, Cougar, Sable, Taurus, Tempo, Thunderbird and Topaz, connect ohmmeter between circuit No. 150 (Dark Green/White wire) and circuit No. 57 (Black wire).
On 1992 Crown Victoria and Grand Marquis, connect ohmmeter between circuit No. 679 (Gray/Black wire) and circuit No. 359 (Gray/Red wire). On Escort and Tracer, connect ohmmeter between circuit No. 57 (Blue wire, or thin Green wire on 1.8L) and circuit No. 59 (White/Black wire).
On 1991 Crown Victoria, Grand Marquis and Town Car and 1991-92 Mustang, disconnect VSS and connect ohmmeter between VSS terminals. On all models, a reading of 200-300 ohms should be obtained. A reading of zero ohms indicates a shorted coil, and a high reading indicates an open coil in sensor or open wire in harness.
If test was performed at amplifier connector, repeat test at sensor terminals. Replace sensor if resistance is not within 200-300 ohms. Repair wire harness if sensor resistance is okay.
If ohmmeter reads 200-300 ohms and speedometer operates properly within needle waver, sensor is probably good. If necessary, substitute a known good sensor to check operation.

NOTE: DO NOT use test light to test any circuit connected to amplifier.