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/physical check for the following conditions:
| • | A faulty mating of the connector halves or a terminal not fully
seated in the connector (backed out). |
| • | An improperly formed or damaged terminal. |
| • | All of the connector terminals in the problem circuit should
be carefully tested for proper contact tension. |
| • | A faulty terminal to wire connection. This requires removing the
terminal from the connector body. |
Road test the vehicle with a digital multimeter (DMM) connected to
the suspected circuit. An abnormal voltage when the 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 help find intermittent faults:
| • | The Snapshot feature can be triggered to capture and store the
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 the scan tool 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 Records 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 the memory, disconnect the
manifold absolute pressure (MAP) sensor and idle the engine until the MIL
is illuminated. DTC P0107 should be stored and kept in memory when ignition
is turned off. If the DTC is not stored, the PCM is faulty. When this test
is completed, make sure that you clear the DTC P0107 from memory.
An intermittent MIL with no stored DTC may be caused by the following:
| • | An ignition coil shorted to ground and arcing at ignition wires
or spark plugs. |
| • | The MIL wire to the PCM shorted to ground. |
Inspect for improper installation of electrical options such as lights,
cellular phones etc. Route ignition control module (ICM) wiring away from
secondary ignition wires and the ignition coils. Inspect all of the wires
from the PCM to the ICM for faulty connections.
Test for an open diode across the A/C compressor clutch, and any other
open diodes. Refer to
A/C Compressor Controls
.
