Once diagnostic codes have been retrieved from the ECU keep alive memory, it is advisable to erase the codes and road test the vehicle. 'Me purpose of this procedure is to confirm that the problem(s) will be present during your diagnosis.
If the diagnostic code re-occurs, the problem can be considered a hard fault and troubleshooting will be routine. If the diagnosis code does not re-occur, the problem is either intermittent or was inadvertently stored during a previous service procedure.
If an intermittent fault is suspected, a physical check of the indicated circuit must be performed by flexing connectors and harnesses at likely failure points while monitoring the circuit with a multimeter or oscilloscope. If the problem is temperature, vibration, or moisture related, the circuit can be heated, lightly tapped, or sprayed with water to simulate the failure conditions. Attempting to troubleshoot intermittent problems using the normal diagnostic routines will likely result in a misdiagnosis and wasted time.
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