86A-6V2 MR-413-X44-86A100$010.mif
RADIO
Fault finding – Introduction86A
R01-08
Vdiag No.: A4
4. FAULT FINDING PROCEDURE (continued)
4.1 Wiring check
Fault finding problems
Disconnecting the connectors and/or manipulating the wiring may temporarily clear the cause of a fault.
Electrical measurements of voltage, resistance and insulation are generally correct, especially if the fault is not
present when the analysis is made (stored fault).
Visual inspection
Look for damage under the bonnet and in the passenger compartment.
Carefully check the fuses, insulators and wiring harness routing.
Look for signs of oxidation.
Physical inspection
When handling the wiring, use the diagnostic tool to detect any change in the status of the faults from "stored" to
"present".
Make sure that the connectors are firmly secured.
Apply light pressure to the connectors.
Twist the wiring harness.
If there is a change in status, try to locate the source of the fault.
Checking earth insulation
This check is carried out by measuring the voltage (multimeter in voltmeter mode) between the suspect connection
and the 12 V or 5 V. The correct measured value is 0 V.
Checking insulation against + 12 V or + 5 V
This check is carried out by measuring the voltage (multimeter in voltmeter mode) between the suspect connection
and the earth. In the first instance, the earth may be taken on the chassis. The correct measured value should be 0 V
Continuity check
A continuity check is carried out by measuring the resistance (multimeter in ohmmeter mode), with the connectors
disconnected at both ends. The expected result must be between: 0 Ω < X < 2 Ω for every connection. The line must
be fully checked, and the intermediate connections are only included in the method if this saves time during the fault
finding procedure. The continuity check on the multiplex lines must be carried out on both wires. The measured
value must be between: 0 Ω < X < 2 Ω.
Checking the supply
This check may be carried out using a test light (21 W or 5 W depending on the maximum authorised load)
