Important Preliminary Checks Before Starting
Before using this section, perform the Powertrain OBD System Check and
verify all of the following items are true:
| • | The PCM and MIL are operating correctly. |
| • | There are no DTCs stored. |
| • | Ensure that the engine coolant temperature is not above 128°C
(262°F). This condition will cause the PCM to operate in Coolant Hot Mode.
While in Coolant Hot Mode, the PCM will turn fuel OFF to three cylinders
to keep engine temperatures from reaching damaging levels. Coolant
Hot Mode will be perceived as a lack of power, miss, or rough idle.
If the vehicle is operating in Coolant Hot Mode, refer to Engine Overheating. |
| • | Verify the customer complaint and locate the applicable symptoms.
Perform the procedure included in the symptom diagnostic table. |
Visual/Physical Checks
Several of the symptom procedures call for a visual/physical inspection.
A careful visual/physical inspection can aid in correcting a problem without
further checks and can save valuable time. A visual/physical inspection
should include the following items:
| • | PCM grounds for being loose, corroded, or in an improper location. |
| • | Vacuum hoses for splits, kinks, and improper connections. The
proper connections are shown on the Vehicle Emission Control Information label.
Check the vacuum hoses for any type of leak or restriction. Refer
to
Emission Hose Routing Diagram
. |
| • | Inspect the air intake ducts for collapsed or damaged areas. |
| • | Check for air leaks at throttle body mounting area, Mass Air Flow
(MAF) sensor, and intake manifold sealing surfaces. |
| • | Inspect the ignition wires for cracking, hardness, proper routing
and carbon tracking. |
| • | Inspect the wiring for improper connections, pinches and cuts. |
The following Symptom tables are located in this section:
| • | Lack of Power, Sluggishness, or Sponginess |
| • | Hesitation, Sag, Stumble |
| • | Rough, Unstable, or Incorrect Idle, Stalling |
| • | Restricted Exhaust System Check |
Visual/Physical Checks
Several of the symptom procedures call for a visual/physical inspection.
A careful visual/physical inspection can aid in correcting a problem without
further checks and can save valuable time. A visual/physical inspection
should include the following items:
| • | PCM grounds for being loose, corroded, or in an improper location. |
| • | Vacuum hoses for splits, kinks, and improper connections. The
proper connections are shown on the Vehicle Emission Control Information label.
Check the vacuum hoses for any type of leak or restriction. |
| • | Air intake ducts for collapsed or damaged areas. |
| • | Air leaks at throttle body mounting area, Mass Air Flow (MAF)
sensor and intake manifold sealing surfaces. |
| • | Ignition wires for cracking, hardness, proper routing and carbon
tracking. |
| • | Wiring for improper connections, pinches and cuts. |
Important: 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:
| • | 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 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 Tech 2 have
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 Tool's 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 check, disconnect MAP sensor and
idle engine until the MIL (Service Engine Soon) comes ON. DTC P0107
should be stored and kept in memory when ignition is turned OFF. If not
the 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. |
If the intermittent condition exists as a start and then stall , check
for DTCs relating to the vehicle theft deterrent system.
Check for improper installation of electrical options such as lights,
cellular phones etc. Route Ignition Control Module (ICM) wiring away from
secondary ignition wires and ignition coils . Check all wires from the
PCM to the ignition control module for poor connections.
Check for open diode across A/C compressor clutch and check for other
open diodes. Refer to Power Distribution Schematics.
If problem has not been found, refer to
Engine Controls Connector End Views
.
