Inspections
| Action
|
DEFINITION:
The condition is not currently present but the condition is indicated in DTC
History.
OR
There is a customer concern, but the symptom cannot currently be duplicated
if the condition is not DTC-related.
|
Visual/Physical Inspection
| This step is an important
aid for locating a condition without extensive testing. Inspect the following
items:
| • | The wiring harness for damage or for cuts |
| • | A misrouted harness that is too close to high voltage or to the
high current devices such as the secondary ignition components, the motors,
and the generators. These components may induce an electrical noise
on a circuit that could interfere with the normal circuit operation. |
| • | The vacuum hoses for proper routing, for correct connections,
for splits, or for kinks. |
| • | Verify the Mass Air Flow (MAF) sensor is installed correctly.
The arrows on the housing should point toward the engine. |
| • | Air leaks at the throttle body mounting area, the MAF, and the
intake manifold sealing surfaces |
| • | The PCM and the body grounds for being clean and tight. |
| • | The battery connections for being clean and tight. |
|
Harness and Connector Inspection
|
| • | Many intermittent conditions occur with harness and connector
movement that is caused by vibration, by engine torque, by rough pavement,
or by component operation. Refer to
Testing for Electrical Intermittents
in Wiring Systems. |
| • | Excessive circuit resistance can cause a component to be inoperative.
If the suspect component does not respond to the scan tool commands, inspect
all the related circuits for excessive resistance. Refer to
Testing for Continuity
in Wiring Systems. |
|
Duplicating Failure Conditions
| Where applicable, the Freeze Frame/Failure Records data
can be used in order to duplicate the conditions during which a DTC
sets.
- Review and record the Freeze Frame/Failure Records data.
- Use the scan tool in order to clear DTCs.
- Turn OFF the ignition for 30 seconds.
- Operate the engine as close to the conditions that were noted
in the Freeze Frame/Failure Records. The engine must also be operating within
the Conditions for Running the DTC. Refer to the Conditions for Running
the DTC.
- Monitor the DTC Status for the DTC being tested. The scan tool
will indicate Ran, when the enabling conditions have been met. The scan tool
will also indicate whether the DTC passed or failed.
| • | The J 42598
Vehicle Data recorder allows the customer or the technician to drive the
vehicle, and to capture the data when the intermittent condition occurs.
Pressing a button on the Vehicle Data Recorder, while the intermittent
condition is present, records PCM data which can be used to isolate the
condition. |
| • | An alternate method is to drive the vehicle with the DMM J 39200
connected to the suspected
circuit. An abnormal reading on the DMM when the condition occurs may help
to locate the condition. |
| • | Compare the Freeze Frame/Failure Records with the typical values
in the Scan Tool Data List. |
|
Scan Tool Snapshot
| The scan tool can be set
up to take a snapshot of the parameters available via the serial data.
The Snapshot function records live data during a period of time.
The recorded data can be played back and analyzed. The scan tool
can also graph the parameters individually or in combinations of parameters
for comparison. The snapshot can be triggered manually when the symptom
is noticed, or can be set up in advance in order to trigger when a
DTC sets.
An abnormal value captured in the recorded data may point to a system
or to a component that needs further investigation.
Refer to the scan tool user instructions for more information on the
Snapshot function.
|
Intermittent Malfunction Indicator Lamp (MIL) with NO DTCs
| The following
conditions may cause an intermittent MIL and no DTCs:
| • | Electrical system interference caused by a malfunctioning relay,
by a PCM-controlled solenoid, or by switch. |
| • | Improper installation of non-factory add-on accessories such as: |
| • | The Malfunction Indicator Lamp (MIL) circuit intermittently shorted
to ground |
|
Additional Inspections
| Test for an open diode across
the A/C compressor clutch. Inspect for other open diodes.
Inspect for improper installation of non-factory add-on accessories
such as:
Excessive circuit resistance can cause a component to be inoperative.
If the suspect component does not respond to scan tool commands, then inspect
all related circuits for excessive resistance. Refer to
Testing for Continuity
in Wiring Systems.
Test the generator for a bad rectifier bridge that may induce AC electrical
noise to the electrical system. Refer to
Diagnostic Starting Point - Engine Electrical
in Engine Electrical.
|
