Inspection/Test
| Action
|
DEFINITION: The problem is not currently
present but is indicated in DTC History.
OR
There is a customer complaint, but the symptom can not currently be
duplicated, if the problem is not DTC related.
|
Preliminary Inspection
|
| • | Refer to
Symptoms
, Important
Preliminary Inspection Before Starting. |
| • | The fault must be present to locate a problem using the DTC table.
If a fault is intermittent, the use of DTC Tables may result in the replacement
of good parts. |
|
Harness/Connector
| Many intermittent open or shorted circuits come and go
with harness or connector movement caused by vibration, engine torque,
bumps/rough pavement, etc. Test for this type of condition by performing
the applicable procedure from the following list:
| • | Move related connectors and wiring while monitoring the appropriate
scan tool data. |
| • | Move related connectors and wiring with the component commanded
ON and OFF with the scan tool. Observe the components operation. |
| • | With the engine running, move related connectors and wiring while
monitoring engine operation. |
If harness or connector movement affects the data displayed, component
or system operation, or engine operation inspect and repair the harness and
connections as necessary.
Refer to Electrical Connections or Wiring in this table.
|
Electrical Connections or Wiring
| Poor electrical connections or terminal tension
or wiring problems cause most intermittents. Perform a careful inspection
of the suspected circuit for the following:
| • | Inspect for poor mating of the connector halves, or terminals
not fully seated in the connector body, backed-out. |
| • | Inspect for improperly formed or damaged terminals. Test for poor
terminal tension. |
| • | Inspect for poor terminal to wire connections including terminals
crimped over insulation. This requires removing the terminal from the connector
body. |
| • | Inspect for 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. Look for swollen and stiff
sections of wire in the suspect circuits. |
| • | Inspect for wires that are broken inside the insulation. |
| • | Inspect the harness for pinched, cut or rubbed through wiring. |
| • | Make sure wiring does not come in contact with hot exhaust components. |
Refer to
Testing for Intermittent Conditions and Poor Connections
.
|
PCM Power and Grounds
| Poor power or ground
connections can cause widely varying symptoms.
| • | Test all PCM power circuits. Many vehicles have multiple circuits
supplying power to the PCM. Inspect connections at the PCM connectors, fuses,
and any intermediate connections between the power source and the PCM.
A test lamp or a DMM may indicate that voltage is present, but neither
tests a circuit's 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 only when
the component or connection is cold, or only when it is hot. The heat that
affects the circuit can be underhood/engine generated, or from the circuit
itself due to a poor connection, or 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 Vehicle Data Recorder 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 EMI or other
types of electrical noise. Inspect for the following conditions:
| • | A misrouted harness that is too close to high voltage and high
current devices such as secondary ignition components, motors, generator etc.
These components may induce electrical noise on a circuit that
could interfere with normal circuit operation. |
| • | Electrical system interference caused by a malfunctioning relay,
PCM driven solenoid or switch. They 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, cell phones, etc. these accessories may lead to an emission
related 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. If a DTC is determined to be intermittent,
and the tests in this section do not reveal a problem, refer to
Powertrain Control Module Diagnosis
. |
| • | Test for an open diode across the A/C compressor clutch and
for other open diodes. |
| • | Test the generator for a bad rectifier bridge that may be allowing
AC noise into the electrical system. Refer to
Diagnostic Starting Point
in Engine Electrical. |
|
Incorrect PCM Programming
| 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/calibration.
Refer to
Powertrain Control Module Replacement/Programming
.
Important:: DO NOT re-program the PCM with the SAME software/calibration files
that are already present in the PCM. This is not an effective repair for any
type of driveability problem.
|
Duplicating Failure Conditions
| If none of the previous tests are successful,
attempt to duplicate and/or capture the failure conditions.
Freeze Frame and Failure Records data (where applicable) contains the
conditions that were present when the DTC set.
- Review and record Freeze Frame/Failure Records data.
- Clear DTCs using the scan tool.
- Turn the key to OFF and wait 15 seconds.
- Operate the vehicle under the same conditions that were noted
in Freeze Frame and Failure Records data (as closely as possible). The vehicle
must also be operating within the conditions for running the
DTC. Refer to Conditions for Running the DTC in the supporting
text of 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 a DMM J 39200
connected.
|
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 DTC sets.
An abnormal value captured in the recorded data may point to a system
or 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 is connected to
the 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.
|
