Vehicle Speed Sensor: Testing and Inspection

VEHICLE SPEED SENSOR

OPERATION
- The vehicle speed sensor is incorporated within the speedometer; it converts vehicle speed data to pulse signals and inputs those signals to the engine control module. The engine control module, based upon those signals, regulates the idle air control motor, etc.
- The vehicle speed sensor, by intermitting by the lead switch the flow (to ground) of the approximately 5 V voltage applied from the engine control module, produces vehicle speed signals.

TROUBLESHOOTING HINTS
If there is damaged or disconnected wiring or a short-circuit in the vehicle speed sensor signal circuit, the engine may stall when the vehicle speed is reduced and the vehicle is stopped.

HARNESS INSPECTION





STEP 1. Check for continuity in the vehicle speed sensor output circuit.
- Engine control module connector: Disconnected
- Move the vehicle.

Continuity: Continuity and no-continuity are repeated alternately.

OK: GO TO STEP 4
NG: GO TO STEP 2





STEP 2. Check for an open or short-circuit between the vehicle speed sensor and the engine control module.
- Engine control module connector: Disconnected
- Vehicle speed sensor connector: Disconnected

OK: GO TO STEP 3
NG: Repair the harness. (A1 - 86)





STEP 3. Check for continuity in the ground circuit.
- Vehicle speed sensor connector: Disconnected

OK: GO TO STEP 4
NG: Repair the harness. (B13 - Ground)





STEP 4. Measure the applied voltage.
- Vehicle speed sensor connector: Disconnected
- Engine control module connector: Connected
- Ignition switch: ON

Voltage (V): 4.5 - 4.9

OK: STOP
NG: Replace the engine control module.


REED SWITCH CHECK
(1) Check that the speedometer operates correctly.




(2) Start the engine. Do not disconnect the connectors. Check the continuity between terminals (1) and (2) while moving slowly the vehicle forward. The continuity and discontinuity should alternate.