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
| Refer
to
Symptoms - Engine Controls
before
starting.
|
Harness/Connector
| Many intermittent open or shorted circuits
come and go with harness/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 a 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/system
operation, or engine operation, inspect and repair the harness/connections
as necessary.
Refer to
Wiring Repairs
in Wiring Systems.
|
Electrical Connections or Wiring
|
| • | Poor electrical connections/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/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 that wiring does not come 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/component connectors, fuses, and
any intermediate connections between the power source and the module/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/connection
reaches normal operating temperature. The condition may occur only when the
component/connection is either cold or hot. |
| • | 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 conditions: |
| - | High ambient temperatures |
| - | Underhood/engine generated heat |
| - | Circuit generated heat due to a poor connection, or high electrical
load |
| - | Higher than normal load conditions, 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/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/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,
a PCM driven solenoid or switch--These conditions 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 J 42598
Vehicle Data Recorder . |
| • | 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/calibration files have been released for this
vehicle. |
| | 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.
|
| • | Verify that the PCM contains the correct software/calibration. If incorrect
programming is found, reprogram the PCM with the most current software/calibration.
Refer to
Powertrain Control Module Programming
. |
|
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, where applicable, contains
the conditions that were present when the DTC set. |
| 1. | Review and record Freeze Frame/Failure Records data. |
| 2. | Clear the DTCs with a scan tool. |
| 3. | Turn the key to OFF and wait 15 seconds. |
| 4. | Operate the vehicle under the same conditions that were noted
in Freeze Frame/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. |
| 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
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.
|
