No real-time speed signal from motion sensor
* Check the wiring and the connectors to the motion sensor and the tachograph: - Damaged wiring or connector? - Loose connector? - Poor connection? * Check the component pin assignment for the real-time motion sensor pulse signal: - Motion sensor: Pin 3 (output). - Tachograph: Pin B3 (input). - Connections between the motion sensor and the tachograph. * Check the real-time motion sensor pulse signal voltage levels: - High level shall be min: power supply from tachograph – 1,5 V. - Low level shall be max: 0,8 V. * Replace defective components.
What you'll see
No driver-visible symptom recorded.
System reaction
MC21/EV301: * Warning message with error text: "sensor fault" together with Memory Code 21 is shown in the tachograph display. * The warning message will be displayed repetitively every hour until the cause is withdrawn. * Event stored in the tachograph memory * Event stored and in the inserted tachograph card. * System event in TCO1 CAN message is set to active. * Tachograph warning (amber T) is displayed in the instrument cluster.
Diagnostic depth
Error during sensor communication. No real-time speed pulse signal from motion sensor.
* Fault in the cable harness * Sensor fault