An intermittent condition may or may not store a DTC or
illuminate the Malfunction Indicator Lamp (MIL) . DO NOT use the Diagnostic
Trouble Code (DTC) charts for intermittent problems. The fault must be present
to locate the problem.
Most intermittent problems are caused by loose electrical connections
or malfuctioning wiring. Perform a careful visual/physical check for the following
conditions:
| • | Poor mating of the connector halves or a terminal not fully seated
in the connector (backed out). |
| • | Improperly formed or damaged terminal. |
| • | All connector terminals in the problem circuit should be carefully
checked for proper contact tension. |
| • | Poor terminal to wire connection. This requires removing the
terminal from the connector body to check. |
Road test the vehicle with a J 39200
Digital Multimeter connected to monitor voltage on a suspected circuit. An
sudden change in voltage when the malfunction occurs is an indication that
there is a fault in the circuit being monitored.
Use a scan tool to help detect intermittent conditions. The scan tool
has several features that can be used to locate an intermittent condition.
Use the following features to find intermittent faults:
| • | The Snapshot feature can be triggered to capture and store engine
parameters within the scan tool when the malfunction occurs. The stored information
then can be reviewed by the service technician to determine what caused the
malfunction. |
| • | Viewing the Freeze Frame data or Failure Records data can also
aid in locating an intermittent condition. Review and record the information
in the freeze frame or failure record associated with the intermittent DTC
being diagnosed. The vehicle can then be driven within the conditions that
were present when the DTC originally set. |
Loss of diagnostic code memory. To check, disconnect the MAF sensor
and idle engine until a DTC sets . DTC P0102 should be stored and kept in
memory when ignition is turned OFF. If DTC P0102 does not remain in memory,
the PCM is malfunctioning. When this test is completed, make sure that you
clear the DTC P0102 from memory.
An intermittent MIL with no stored DTC may be caused by the following
conditions:
| • | Ignition system secondary components arcing to wiring harnesses. |
| • | MIL control circuit wiring intermittently shorted to ground. |
Check for improper installation of electrical options such as lights,
cellular phones etc. Ensure that engine harness routing is correct. Check
all wiring between the PCM and the ignition control module for poor connections.
Check for open diode across A/C compressor clutch and check for other
open diodes. Refer to wiring diagrams in Electrical Diagnosis
.
