Inspection/Test
| Action
|
DEFINITION:
The problem is not currently present but is indicated in diagnostic trouble
code (DTC) history. Or, there is a customer complaint, but the symptom cannot
currently be duplicated, if the problem is not DTC related.
|
Preliminary Inspection
|
| • | The fault must be present to locate a problem using the diagnostic
trouble code (DTC) table. If a fault is intermittent, the use of DTC tables
may result in the replacement of good parts. |
|
Harness/Connector
Test
| Many
intermittent open or shorted circuits come and go with harness/connector movement
caused by vibration, engine torque, and rough pavement. Test for this
type of condition by performing the applicable procedure from the
following list:
| • | Move the related connectors and the wiring while monitoring the
appropriate scan tool data. |
| • | Move the related connectors and the wiring with the component
commanded ON, and OFF, with the scan tool. Observe the components operation. |
If the harness or the connector movement affects the data displayed,
the component and system operation, or the engine operation, inspect and repair
the harness and connections as necessary. Refer to
Wiring Repairs
, and
Connector Repairs
in Wiring Systems.
|
Electrical Connections or Wiring
| Faulty electrical
connections and terminal tension or wiring problems cause most intermittents.
Perform a careful inspection of the suspected circuit for the following
conditions:
| • | Faulty mating of the connector halves |
| • | Terminals not fully seated in the connector body |
| • | Improperly formed or damaged terminals--Test for faulty terminal
tension. |
| • | Faulty terminal to wire connections including terminals crimped
over insulation--This requires removing the terminal from the connector
body. |
| • | Corrosion or water intrusion--Pierced or damaged insulation
can allow moisture to enter the wiring. The conductor can corrode inside
the insulation, with little visible evidence. Inspect for swollen and stiff
sections of wire in the suspect circuits. |
| • | Broken wires inside the insulation |
| • | Pinched, cut, or rubbed-through wiring in the harness |
Ensure that wiring and/or harness does not contact with hot exhaust
components.
Refer to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems.
|
PCM Power and Grounds
| Faulty power or
ground connections can cause widely varying symptoms.
| • | Test all powertrain control module (PCM) power circuits. Many
vehicles have multiple circuits supplying power to the PCM. Inspect connections
at the PCM connectors, the fuses, and any intermediate connections between
the power source and the PCM. A test lamp or a digital multimeter (DMM)
may indicate that voltage is present, but neither tool tests a circuits
ability to carry sufficient current. Ensure that the circuit can carry the
current necessary to operate the component. Refer to
Power Distribution Schematics
in Wiring Systems. |
| • | Test all PCM ground and system ground circuits. The PCM may have
multiple ground circuits. Other components in the system may have separate
grounds that may also need to be tested. Inspect grounds for clean and tight
connections at the grounding point. Inspect the connections at the component
and in splice packs, where applicable. Ensure that the circuit can carry
the current necessary to operate the component. Refer to
Ground Distribution Schematics
in Wiring Systems. |
|
Temperature Sensitivity
| An intermittent condition may occur when the component or connection
is cold or hot. The heat that affects the circuit can be underhood or engine
generated, or generated from the circuit due to a faulty connection, or due
to a high electrical load.
Information from the customer may help to determine if the trouble follows
a pattern that is temperature related. Freeze Frame/Failure Records, Snapshot,
or the J 42578
Vehicle
Data Recorder (VDR) data may help with this type of intermittent condition,
where applicable.
|
Electromagnetic Interference (EMI) and Electrical Noise
| Some electrical
components or circuits are sensitive to electromagnetic interference (EMI)
or other types of electrical noise. Inspect for the following conditions:
| • | A misrouted harness that is too close to high voltage or high
current devices such as secondary ignition components, motors, and generators.
These components can induce electrical noise on a circuit that could interfere
with normal circuit operation. |
| • | Electrical system interference caused by a malfunctioning relay,
a powertrain control module (PCM) driven solenoid, or a switch. Malfunctioning
components can cause a sharp electrical surge. Normally, the problem
will occur when the malfunctioning component is operating. |
| • | Improper installation of non-factory or aftermarket add-on accessories
such as lights, 2-way radios, amplifiers, electric motors, remote starters,
alarm systems, and cell phones can cause certain conditions. These accessories
can lead to an emission-related On-Board Diagnostic (OBD) II failure
while in use, but do not fail when the accessories are not in use. Refer
to
Checking Aftermarket Accessories
in
Wiring Systems. |
| • | Test for an open diode across the air conditioning (A/C) compressor
clutch and test for other open diodes. |
| • | Test the generator for a bad rectifier bridge that may be allowing
AC noise into the electrical system. |
|
Incorrect PCM Programming
|
Important: DO NOT re-program the powertrain control module (PCM) with the SAME
software/calibration files that are already present in the PCM. This is not
an effective repair for any driveability problem.
There are only a few situations where reprogramming a PCM is appropriate:
| • | A new service PCM is installed. |
| • | A PCM from another vehicle is installed. |
| • | Revised software/calibration files have been released for this
vehicle. |
Verify that the PCM contains the correct software/calibration. If incorrect
programming is found, re-program the PCM with the most current software and/or
calibration. Refer to
Powertrain Control Module Programming
.
|
Duplicating Failure Conditions
| If none of the previous
inspections were successful, attempt to duplicate and/or capture the failure
conditions.
Freeze Frame/Failure Records data, where applicable, contains the conditions
that were present when the diagnostic trouble code (DTC) set.
- Review and record Freeze Frame/Failure Records data.
- Clear the DTCs with a scan tool.
- Turn the key to OFF and wait 15 seconds.
- Operate the vehicle under the same conditions that were noted
in Freeze Frame/Failure Records data. The vehicle must also be
operating within the Conditions for Running the DTC. Refer to
Conditions for Running the DTC in the supporting text for the DTC being
diagnosed.
- Monitor DTC Status for the DTC being tested. The scan tool will
indicate Ran when the enabling conditions have been satisfied long enough
for the DTC to run. The scan tool will also indicate whether
the DTC passed or failed.
An alternate method is to drive the vehicle with the digital multimeter
(DMM) connected to a suspected circuit. An abnormal reading on the DMM when
the problem occurs can help to locate the problem.
|
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 singly 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 diagnostic
trouble code (DTC) sets.
An abnormal value captured in the recorded data may indicate a system
or a component that needs to be investigated further.
Refer to the scan tool user instructions for more information on the
Snapshot function.
|
Vehicle Data Recorder
| The J 42598
Vehicle Data Recorder (VDR) is connected to the data link connector
(DLC) and sent with the customer. The vehicle data recorder captures data
for later retrieval and analysis by the technician. Refer to the vehicle
data recorder user instructions for more information.
|
