An intermittent condition may or may not turn on the malfunction indicator lamp
(MIL) or store a diagnostic trouble code (DTC).
Preliminary Checks
Perform a visual check to locate the cause of the problem.
| • | The fault must be present to locate the problem. If a fault is intermittent,
the use of DTC tables may result in the replacement of good parts. |
Electrical Connections or Wiring
Poor electrical connections or wiring can cause most intermittent problems.
Perform a careful check of the suspected circuit for the following:
| • | Check for poor mating of the connector halves, or terminals not fully
seated in the connector body, backed-out. |
| • | Check for improperly formed or damaged terminals. Carefully reform or
replace all the connector terminals in the problem circuit to ensure the proper contact
tension. |
| • | Check for poor terminal to wire connections. This requires removing the
terminal from the connector body to check. |
Road Test
If a visual/physical check does not locate the cause of the problem, drive the
vehicle with a DMM connected to a suspected circuit or use a scan tool. An abnormal
voltage or scan reading, when the problem occurs, indicates the problem may be in
that circuit.
Intermittent Malfunction Indicator Lamp (MIL)
The following can cause an intermittent MIL and no DTCs:
| • | Electrical system interference caused by a malfunctioning relay, ECM driven
solenoid, or switch. The electrical component can cause a sharp electrical surge.
Normally, the problem will occur when the malfunctioning component is operating. |
| • | The improper installation of electrical devices; such as lights, 2-way
radios, electric motors, etc. |
| • | The MIL circuit intermittently shorted to ground. |
