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 cannot currently be duplicated,
if the problem is not DTC related.
|
Preliminary
| Refer to
Symptoms
before starting.
|
Harness/Connector
| Many intermittently open or shorted circuits come and go with harness or connector
movement caused by vibration, engine torque, bumps or rough pavement,
etc. 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 wiring with the component commanded
on and off with the scan tool. Observe the component operation. |
| • | With the engine running, move the related connectors and wiring
while monitoring the engine operation. |
If a harness or connector movement affects the data displayed, component
or system operation, or engine operation, inspect and repair the harness or
the connections as necessary.
Refer to Electrical Connections or Wiring in this table.
|
Electrical Connections or Wiring
|
| • | Poor electrical connections, poor 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. |
| - | Inspect for improperly formed or damaged terminals. Test for poor
terminal tension. |
| - | Inspect for poor terminal-to-wire connections including any terminals
crimped over the insulation. This requires removing the terminal from the
connector body. |
| - | Inspect for corrosion and 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. |
| - | Ensure the wiring does not come in contact with any hot exhaust
components. |
|
Control Module Power and Grounds
Component Power and Grounds
| Poor power or ground connections can cause
widely varying symptoms.
| • | Test all of the 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 the connections at the module and component connectors,
the fuses, and any intermediate connections between the power source
and the module or component. 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 of the 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 the grounds for clean and tight connections at the grounding
point. Inspect the connections at the component and in any 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 or a connection
reaches a normal operating temperature. The condition may occur only when
the component or the connection is cold, or only when the component
or the connection is hot. |
| • | The Freeze Frame, Failure Records, Snapshot, or Vehicle Data Recorder
data may help with this type of intermittent condition, where applicable. |
| • | If the intermittent is related to heat, review the data for a
relationship with the following: |
| - | High ambient temperatures |
| - | Underhood or engine generated heat |
| - | Circuit generated heat due to a poor connection or a high electrical
load |
| - | Higher than normal load conditions (towing, etc.) |
| • | If the intermittent is related to cold, review the data for the
following: |
| - | 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 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 or high
current devices such as the secondary ignition components, any motors, the
generator etc. These components may induce electrical noise
on a circuit that could interfere with the normal circuit
operation. |
| • | Any electrical system interference caused by a malfunctioning
relay, a PCM driven solenoid, or a switch. These components can cause a
sharp electrical surge. Normally, the problem will occur when
the malfunctioning component is operating. |
| • | The 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. Some relays may contain a clamping diode. |
|
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 or calibration files have been released for this
vehicle. |
| | Important:: DO NOT reprogram 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
or capture the failure conditions. |
| • | The Freeze Frame/Failure Records data, where applicable, contains
the conditions that were present when the DTC set. |
| 1. | Review and record the Freeze Frame/Failure Records data |
| 2. | Clear the DTCs using the scan tool. |
| 3. | Turn the key to OFF and wait 15 seconds. |
| 4. | Operate the vehicle as closely as possible within the same conditions
that were noted in the 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 of the DTC being diagnosed. |
| 5. | Monitor the 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 the 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 the 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 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 is connected to
the data link connector (DLC) and sent with the customer. The J 42598
vehicle data recorder captures data
for later retrieval and analysis by the technician. Refer to the vehicle
data recorder user instructions for more information.
|
