STEP 3. Measure the sensor supply voltage at ECM connector by using power plant ECU check harness special tool MB992110.
(1) Disconnect all ECM connectors. Connect the power plant ECU check harness special tool MB992110 between the separated connectors.
(2) Disconnect the engine coolant temperature sensor connector and measure at intake air temperature sensor side.
(3) Turn the ignition switch to the "ON" position.
(4) Measure the voltage between terminal WTS line and ground.- Voltage should be between 4.5 and 4.9 volts.
(5) Turn the ignition switch to the "LOCK" (OFF) position.
Is the measured voltage between 4.5 and 4.9 volts?
Repair or replace the connector(s), or check and repair the harness of open circuit in WTS line between engine coolant temperature sensor connector and ECM connector. Then go to Step 7. Replace the ECM (Refer to Removal and Installation ). Then go to Step 8.