TD John
New Member
Hi Dac5 - Sounds odd as they are electronic, fed from the same place and display fault codes if the signal is lost? :scratching_chin:
See below from Rave;-
Speedometer
The speedometer is electronically operated and contains an LCD. Each model has a maximum scale indication of 136 mph (220 km/h).
The speedometer is driven by CAN messages from the ABS ECU. The messages are generated by an ABS wheel speed sensor which produces pulses as the reluctor rotates. The instrument pack microprocessor processes the incoming CAN message from the ABS ECU and converts it into electrical signals for speedometer operation.
If the CAN message fails for more than 64ms the microprocessor will terminate speedometer operation and record a fault flag. The recorded fault can be accessed using TestBook.
The odometer uses the same CAN messages as the speedometer to calculate the distance travelled. If the CAN message fails, the LCD will display the odometer distance and 'Error' alternately for one second each.
If the speedo does not cut out and the odometer does not flash error - then the system thinks all is ok. It's all electronic (after the pick-up from the wheel sensor) so I guess only a diagnostic check may tell?
Could possiby be a faulty wheel sensor giving intermittent output and reading slow but that should affect both speedo and odometer?
Have a bit of a read up on the Rave (instruments operation) for more info.
See below from Rave;-
Speedometer
The speedometer is electronically operated and contains an LCD. Each model has a maximum scale indication of 136 mph (220 km/h).
The speedometer is driven by CAN messages from the ABS ECU. The messages are generated by an ABS wheel speed sensor which produces pulses as the reluctor rotates. The instrument pack microprocessor processes the incoming CAN message from the ABS ECU and converts it into electrical signals for speedometer operation.
If the CAN message fails for more than 64ms the microprocessor will terminate speedometer operation and record a fault flag. The recorded fault can be accessed using TestBook.
The odometer uses the same CAN messages as the speedometer to calculate the distance travelled. If the CAN message fails, the LCD will display the odometer distance and 'Error' alternately for one second each.
If the speedo does not cut out and the odometer does not flash error - then the system thinks all is ok. It's all electronic (after the pick-up from the wheel sensor) so I guess only a diagnostic check may tell?
Could possiby be a faulty wheel sensor giving intermittent output and reading slow but that should affect both speedo and odometer?
Have a bit of a read up on the Rave (instruments operation) for more info.
