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 in order 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:
| • | Inspect for faulty mating of any connector halves or any terminals
not fully seated in the connector (backed out). |
| • | Check for improperly formed or damaged terminals. |
| • | Test all connector terminals in the problem circuit for the proper
contact tension. |
| • | Inspect for faulty terminal to wire connections. This requires
removing the terminal from the connector body. |
Road test the vehicle with a DMM connected to a suspect circuit.
An abnormal voltage when a 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 can then be reviewed by the service technician in order to determine
what caused the malfunction. |
| • | 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. |
Check for a loss of diagnostic code memory. Disconnect the MAP
sensor and idle the engine until the MIL illuminates. The DTC P0107
should be stored and kept in memory when the ignition
is turned OFF. If not, the PCM is faulty. When this
test is completed, clear the DTC P0107 from memory.
An intermittent MIL with no stored DTC may be caused by the following
conditions:
| • | Inspect the ignition coil shorted to ground and arcing at the
ignition wires or the spark plugs. |
| • | Check the MIL wire to the PCM for a short to ground. |
Check for improper installation of electrical options such as lights,
cellular phones, etc. Route the ignition control (IC) module wiring
away from secondary ignition wires and ignition coils
. Check all wires from the PCM to the ignition control
module for faulty connections.
Check for an open diode across the A/C compressor clutch and other
open diodes. Refer to
Engine Controls Schematics
.
