Intermittents/History DTCs

History codes are those indicating that the CCM previously detected a fault which later disappeared. Any DTC that has a 1 as its first digit is a history DTC. Examples are: 120, 132, 137 etc. The reason could be either that the fault is a true intermittent, only happening occasionally, or that the system for which the DTC is not currently being operated. An example of this would be DTC 143 (key resistor short to battery/open) CKT 1073 could have an intermittent short to B+. For this reason, if a DTC is displayed as a history DTC and the fault cannot be found easily, try clearing the DTC and operating the system that the DTC applies to. If the DTC resets, it can be assumed that the condition is present.

Most intermittents are caused by faulty electrical connections or wiring, although occasionally a sticking relay or solenoid can be a problem. Some items to check are:

^ Poor mating of connector halves, or terminals not fully seated in the connector body (backed out).

^ Damaged connector body, exposing the terminals to moisture and dirt, as well as, not maintaining proper terminal orientation with the component or mating connector.

^ Improperly formed or damaged terminals. All connector terminals in problem circuits should be checked carefully to ensure good contact tension. Use a corresponding mating terminal to check for proper tension. Refer to "Checking Terminal Contact" for the specific procedure.

^ The J 35616-A Connector Test Adapter Kit must be used whenever a diagnostic procedure requests checking or probing a terminal. Using the test adapter will ensure that no damage to the terminal will occur, as well as, giving an idea of whether contact tension is sufficient. If contact tension seems incorrect, refer to "Checking Terminal Contact" for specifics.

^ Poor terminal-to-wire connection. Checking this requires removing the terminal from the connector body, outlined in DIAGRAMS. Some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, corrosion in the wire-to-terminal contact area, etc.

^ Wire insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of the vehicle.

^ Wiring broken inside the insulation. This condition could cause a continuity check to show a good circuit, but only if 1 or 2 strands of a multistrand-type wire are intact, resistance could be far too high. This is of particular importance in the PASS-Key(R)II detection circuit, in which resistance is critical.

^ Check for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (see "Troubleshooting Procedures".

To avoid any of the above problems when making wiring or terminal repairs, always follow the instructions for wiring terminal repair outlined in DIAGRAMS.