Voltage supply
â–¶ How to fix
Check the circuits for shorts and breaks. If the fault is found in the tachograph or impulse sensor, the relevant unit must be renewed.
What you'll see
No driver-visible symptom recorded.
System reaction
No system-reaction text recorded.
Diagnostic depth
Detection
The voltage supply to the impulse sensor has been too low. The voltage level should be between 6.5 - 9 V.
Possible cause
Short circuit or break in the lead between the tachograph and the impulse sensor or in the lead for the power supply to the tachograph. There may also be an internal fault in the tachograph or impulse sensor.