The ECM can supply an output signal to operate the vehicle tachograph. The circuit consists of the tachograph signal wire and the common switch return (-) wire.
Refer to the OEM troubleshooting and repair manual for troubleshooting instructions.
Insert one of the test leads into the tachograph signal pin of the 50-pin OEM harness connector. Connect the alligator clip to the multimeter probe.
Insert the other test lead into the tachograph signal pin of the sensor harness connector, and connect the alligator clip to the other multimeter probe. Measure the resistance.
The multimeter must show 10 ohms or less (closed circuit).
If the circuit is not closed, there is an open circuit or the wires in the tachograph connector are reversed. Repair or replace the wire connected to the signal pin in the 50-pin OEM harness connector. Refer to the OEM troubleshooting and repair manual.
Disconnect the 50-pin OEM harness connector from the ECM connector. Disconnect the tachograph from the OEM harness. Set the multimeter to measure resistance.
Touch the test lead to the tachograph signal pin of the 50-pin OEM harness connector. Touch the other multimeter lead to the engine block. Measure the resistance.
The multimeter must show 100k ohms or more (open circuit).
Disconnect the 50-pin OEM harness connector from the ECM connector. Set the multimeter to measure resistance. Insert a test lead into the tachograph signal pin of the 50-pin OEM harness connector.
Insert the other test lead into the first pin of the 50-pin OEM harness connector, and measure the resistance.
The multimeter must show 100k ohms or more (open circuit).
Remove the lead from the first pin and check all other pins, one at a time.
The multimeter must show 100k ohms or more (open circuit) at all pins.
If the multimeter does not show an open circuit at any pin, a short circuit exists between the signal pin and any pin that measures less than 100k ohms.
Repair or replace the OEM harness. Refer to the OEM troubleshooting and repair manual.
Hello, I'm Jack, a diesel engine fan and a blogger. I write about how to fix and improve diesel engines, from cars to trucks to generators. I also review the newest models and innovations in the diesel market. If you are interested in learning more about diesel engines, check out my blog and leave your feedback.
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