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, and the problem is not DTC related.
|
Preliminary
| Refer to
Symptoms - Engine Controls
before starting.
|
Harness/Connector
| Many intermittent
open or shorted circuits come and go with harness and/or connector movement
caused by vibration, engine torque, bumps and/or 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 component operation. |
| • | With the engine running, move related connectors and wiring while
monitoring engine operation. |
If harness or connector movement affects the data displayed, component
and/or system operation, or engine operation, inspect and repair
the harness and/or connections as necessary.
Refer to Electrical Connections or Wiring in this table.
|
Electrical Connections or Wiring
|
| • | Poor electrical connections and/or terminal tension or wiring
problems cause most intermittents. Perform a careful inspection of the
suspected circuit for the following conditions: |
| - | Poor mating of the connector halves, or terminals not fully
seated in the connector body |
| - | Improperly formed or damaged terminals--Test for poor terminal
tension. |
| - | Poor terminal to wire connections including terminals crimped
over insulation--This requires removing the terminal from the connector
body. |
| - | Signs of corrosion and/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. |
| - | Broken wires inside the insulation |
| - | Pinched, cut, or rubbed through wiring in the harness |
| - | Wiring in contact with hot exhaust components |
|
Control
Module Power and Grounds
Component Power and Grounds
| Poor power or ground connections can cause widely varying
symptoms.
| • | Test all control module power circuits. Many vehicles have multiple
circuits supplying power to the control module. Other components in the system
may have separate power circuits that may also need to be tested. Inspect
connections at the module and/or component connectors, fuses, and any
intermediate connections between the power source and the module and/or
component. A test lamp or a DMM may indicate that voltage is present,
but neither tests a circuit 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 control module ground and system ground circuits. The
control module 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 a component and/or connection
reaches normal operating temperature. The condition may occur only when the
component and/or connection is cold, or only when it is hot. |
| • | The following data may help with this type of intermittent condition,
if applicable: |
| • | If the intermittent is related to heat, review the data for a
relationship with the following conditions: |
| - | High ambient temperatures |
| - | Underhood and/or engine generated heat |
| - | Circuit generated heat due to a poor connection, or high electrical
load |
| - | Higher than normal load conditions, such as towing, etc. |
| • | If the intermittent is related to cold, review the data for the
following conditions: |
| - | Low ambient temperatures--In extremely low temperatures,
ice may form in a connection or component. Test for water intrusion. |
| - | The condition only occurs on a cold start. |
| - | The condition goes away when the vehicle warms up. |
| • | Information from the customer may help to determine if the trouble
follows a pattern that is temperature related. |
|
Electromagnetic
Interference (EMI) and Electrical Noise.
| Some electrical components and/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 and/or 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
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 Vehicle Data Recorder later in this table. Non-factory
or aftermarket add-on accessories includes the following components: |
| • | Test for an open diode across the A/C compressor clutch and
for other open diodes. Some relays may contain a clamping diode. |
|
Incorrect
PCM Programming
|
| • | There are only a few situations where reprogramming a powertrain
control module (PCM) is appropriate: |
| - | A new service PCM is installed. |
| - | A PCM from another vehicle is installed. |
| - | Revised software and/or calibration files have been released for
this vehicle. |
| | Important: DO NOT re-program the PCM with the SAME software and/or calibration
files that are already present in the PCM. This is not an effective repair
for any type of driveability problem.
|
| • | Verify that the PCM contains the correct software and/or calibration.
If incorrect programming is found, reprogram the PCM with the most current
software and/or calibration. Refer to
Powertrain Control Module Replacement
. |
|
Duplicating
Failure Conditions
|
| • | If none of the previous tests are successful, attempt to duplicate
and/or capture the failure conditions. |
| • | Freeze Frame/Failure Records data, if applicable, contains the
conditions that were present when the DTC set. |
| 1. | Review and record Freeze Frame/Failure Records. |
| 2. | Clear the DTCs using the scan tool. |
| 3. | Turn OFF the key and wait 15 seconds. |
| 4. | Operate the vehicle under the same conditions that were noted
in Freeze Frame/Failure Records, 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. |
| 5. | 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 DMM connected
to a suspected circuit. An abnormal reading on the DMM when the problem occurs,
may help you 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 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 data link connector
(DLC) and sent with the customer. The J 42598
captures data for later retrieval and analysis by the
technician. Refer to the vehicle data recorder user instructions for
more information.
|
