86D -5V1 MR-413-X44-86D000$010.mif
MULTIMEDIA CONNECTION UNIT
Fault finding – Introduction86D
BIC
Vdiag No.: 14
4. FAULT FINDING PROCEDURE (continued)
4.1. Wiring check
Fault finding problems
Disconnecting the connectors and/or manipulating the wiring may temporarily remove 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
While manipulating the wiring harness, use the diagnostic tool to note any change in fault status from stored to
present.
Make sure that the connectors are properly locked.
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 should be 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 ΩΩ Ω 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 ΩΩ Ω Ω
< X < 2 ΩΩ Ω 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)
4.2. Connector check
Note:
Carry out each requested check visually. Do not remove a connector if it is not required.
Note:
Repeated connections and disconnections alter the functionality of the connectors and increase the risk of poor
electrical contact. Limit the number of connections/disconnections as much as possible.
Note:
The check is carried out on the 2 parts of the connection. There may be two types of connection:
–Connector/Connector.
–Connector/Device.
