Inspections
| Action
|
DEFINITION:
The condition is not currently present but 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. Perform a visual/physical
inspection of the following items:
| • | The wiring harness for damage or cuts |
| • | A misrouted harness that is too close to high voltage/high current
devices such as secondary ignition components, motors and generators--These
components may induce electrical noise on a circuit that may interfere
with normal circuit operation. |
| • | The vacuum hoses for proper routing, connections, splits, or kinks |
| • | Air leaks at the throttle body mounting area, mass air flow sensor
(MAF), and the intake manifold sealing surfaces |
| • | The MAF sensor installation--The arrows on the plastic portion
of the sensor must point towards the engine. |
| • | The powertrain control module (PCM) and body grounds for being
clean and tight |
| • | The battery connections for being clean and tight |
|
Harness/Connector
Inspection
|
| • | Many intermittent conditions occur with harness/connector movement
caused by vibration, engine torque, rough pavement, or 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, test
the related circuits for excessive resistance. Refer to
Testing for Continuity
in Wiring Systems. |
|
Duplicating
Failure Conditions
| Freeze Frame/Failure Records data, where applicable, can be used in
order to duplicate the conditions under which a DTC sets.
- Review and record Freeze Frame/Failure Records data.
- Clear the DTCs using the scan tool.
- Turn OFF the ignition for 30 seconds.
- Operate the engine as close to the conditions that were noted
in Freeze Frame/Failure Records. The engine must also be operating within
the conditions for running the DTC, refer to 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 capture data as 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 DMM connected
to the suspected circuit. An abnormal reading on the DMM when the condition
occurs may help you 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 serial data. The Snapshot function records live data over a
period of time. The recorded data can be played back and analyzed.
The scan tool can also graph parameters individually or in combinations
of parameters for comparison. The snapshot can be triggered manually
at the time the symptom is noticed, or set up in advance to trigger
when a DTC sets.
An abnormal value captured in the recorded data may point to a system
or 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,
PCM controlled solenoid, or switch |
| • | Improper installation of non-factory, aftermarket, add-on accessories
such as cellular phones, alarms, lights, or radio equipment |
| • | The malfunction indicator lamp (MIL) circuit intermittently being
shorted to ground |
|
Additional
Inspections
|
| • | Excessive circuit resistance can cause a component to be inoperative.
If the suspect component does not respond to scan tool commands, test the
related circuits for excessive resistance. Refer to
Testing for Continuity
in Wiring Systems. |
| • | Test for an open diode across the A/C compressor clutch and for
other open diodes. |
| • | Inspect for improper installation of non-factory, aftermarket,
add-on accessories such as cellular phones, alarms, lights, or radio equipment. |
| • | Test the generator for a bad rectifier bridge that may induce
A/C electrical noise to the electrical system. Refer to
Charging System Test
in Engine Electrical. |
|
