A problem may or may not turn ON the malfunction indicator
lamp (MIL) or store a DTC. 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 faulty electrical connections
or wiring. Perform a careful visual and physical inspection for the following
conditions:
| • | Poor mating of the connector halves or a terminal not fully seated
in the connector. |
| • | 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 DMM connected to a suspected circuit.
An abnormal voltage when malfunction occurs is a good 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. This stored information
then can be reviewed by the service technician to see what caused the
malfunction. |
| • | Using a Scan Tools 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 be driven within the
conditions that were present when the DTC originally set. |
Loss of diagnostic code memory. To test, disconnect the MAP sensor
and idle engine until the MIL Service Engine Soon comes ON. DTC P0107
should be stored and kept in memory when the ignition is turned OFF. If
not the powertrain control module (PCM) is faulty. When this test is completed,
make sure that you clear the DTC P0107 from memory.
An intermittent MIL Service Engine Soon with no stored DTC may be caused
by the following:
| • | Ignition coil shorted to ground and arcing at ignition wires
or plugs. |
| • | MIL Service Engine Soon wire to PCM shorted to ground. |
Inspect for improper installation of electrical options such as lights,
cellular phones, etc. Route ignition control (IC) module wiring away from
secondary ignition wires and ignition coils . Inspect all wires from the
PCM to the ignition control module for poor connections.
Test for an open diode across the A/C compressor clutch and test for
other open diodes. Refer to
Wiring Repairs
in
Wiring Systems.
