CM2150 Electronic Control System – 019-093   Vehicle Speed Sensor Circuit

CAUTION  The leads must fit tightly in the connector without expanding the pins in the connector otherwise the connector will be damaged.

Disconnect the original equipment manufacturer (OEM) harness connector from the electronic control module (ECM). Make sure the vehicle speed sensor is connected to the OEM harness.

Insert a test lead into the magnetic vehicle speed sensor signal positive (+) pin in the OEM harness connector. Insert the other lead into the magnetic vehicle speed sensor signal negative (-) pin of the connector.

Connect the two alligator clips to the two probes of the multimeter. Adjust the multimeter to the resistance setting and measure resistance. When measuring the resistance with the sensor connected, refer to the OEM troubleshooting and repair manual for the correct resistance value. If the value is
not correct, there is a problem with the OEM harness, provided that the vehicle speed sensor component has been previously checked.

NOTE: Repair or replace the OEM harness. Refer to Procedure
019-071, or to the OEM troubleshooting and repair manual for OEM harness replacement.

If the value is correct, the circuit
must still be checked for a short circuit to ground and a short circuit from pin-to-pin.

Check for a short circuit to ground. Insert the multimeter probe with attached test lead into the magnetic vehicle speed sensor signal positive (+) pin of the OEM harness connector. Touch the other multimeter probe to the engine block. Measure the resistance. The multimeter
must show an open circuit (100k ohms or more).

If the circuit is
not open, there is a short circuit to ground in the vehicle speed sensor circuit in the engine harness or OEM harness.

Repair the wires which are shorted in the circuit according to the vehicle manufacturer’s procedures.

Check for a short circuit from pin-to-pin. Insert the multimeter probe with attached test lead into the magnetic vehicle speed sensor signal positive (+) pin of the OEM harness connector. Insert the other test lead into all the other pins, one at a time, to check for a short to another pin.

Measure the resistance. The multimeter
must show an open circuit (more than 100k ohms).