Before using the symptom tables, perform the Powertrain
On-Board Diagnostic (OBD) System Check and if directed to do so, the Transmission
On-Board Diagnostic (OBD) System Check. Verify all the following items:
| • | The ECM, TCM, MIL, and the STL operate correctly. |
| • | There are no DTCs stored. |
Verify the customer complaint. Locate the correct symptom in the table.
Perform the procedure included in the symptom table.
Intermittents
Important: A problem may or may not turn on the Malfunction Indicator Lamp (MIL)
and the Service Transmission Lamp (STL) or store a DTC. Do Not use the Diagnostic
Trouble Code (DTC) charts for any intermittent problems. The fault must be
present in order to locate the problem.
Most intermittent problems are caused by poor electrical connections
or 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). |
| • | An improperly formed or damaged terminal. |
| • | All connector terminals in the problem circuit should be carefully
checked for proper contact tension. Refer to Engine Electrical,
Troubleshooting Procedures, Checking Terminal Contact
for a proper
procedure. |
| • | A poor terminal to wire connection. This requires removing the
terminal from the connector body in order to check. Also, check for the terminal
being crimped over the insulation. |
Road test the vehicle with a DVM (J 39200
) connected to a suspected 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 in order to help detect intermittent conditions. The
Tech 1 & Tech 2 have several features that can be used in order to locate
an intermittent condition. Use the following features in order to find the
intermittent faults:
| • | The Snapshot feature can be triggered to capture and store the
engine parameters within the scan tool when the malfunction occurs. You can
review this stored information in order to determine what caused the malfunction,
or what conditions were present when the problem occurred. |
| • | Reviewing the Freeze Frame data can also aid in locating an intermittent
condition. Review and record the information in the freeze frame that is associated
with the intermittent DTC being diagnosed. The vehicle can be driven within
the conditions that were present when the DTC originally set. |
An intermittent MIL with no stored DTC may be caused by the following:
| • | The MIL control circuit to the ECMPCM shorted to ground. |
| • | Poor ECMPCM grounds. Refer to the ECMPCM wiring diagrams. |
If the intermittent condition exists as a start and then a stall, check
for DTC(s) relating to the vehicle theft deterrent system.
Check for improper installation of electrical options such as lights,
cellular phones etc.
Check for open diode across the A/C compressor clutch. Then, check for
other open diodes. Refer to wiring diagrams in Electrical
Diagnosis.
