939003628 - K006 TRIP METER DOES NOT ZERO

With the key on, the trip meter does not zero when the "Km" button in the control panel is operated.
1CHECK USING DIAGNOSTIC EQUIPMENTALL OKPROBLEMS ENCOUNTEREDACTION
Connect the Examiner diagnostic equipment to the diagnostic socket.Check that there are no faults in the instrument panelMove on to Step 2Presence of errorsContinue following the instructions for the diagnostic equipment
2ELECTRICAL CIRCUIT CHECKALL OKPROBLEMS ENCOUNTEREDACTION
Check connections between control panel and instrument panel    See E4010 INSTRUMENT PANEL Move on to Step 3Connections defective, earth or power supply defectiveRestore the correct connections, if necessary, replace the wiring.
3CONTROL PANEL CHECKALL OKPROBLEMS ENCOUNTEREDACTION
Check that the KM button in the control panel is working properlyMove on to Step 4Button defectiveReplace the control panelOp. 5560B56 PANEL WITH MULTIFUNCTION DISPLAY AND HEADLAMP ALIGNMENT SWITCHES BUTTONS R R
4CHECK ON CORRECT OPERATIONALL OKPROBLEMS ENCOUNTEREDACTION
Check that the fault is no longer presentEnd of diagnosis