Inspection or Test
| Action
|
DEFINITION: Whether
the symptom is a DTC or a customer complaint, the condition cannot be duplicated.
|
Preliminary
| Perform the Diagnostic System Check-Engine Controls before starting. Refer
to
Diagnostic System Check - Engine Controls
.
|
Harness or Connector
| Many intermittent open or shorted circuits come and go with harness
or connector movement caused by the following type conditions:
| • | Bumps or rough pavement |
Test for intermittents 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. |
Verify whether the harness or connector movement affects any of the
following systems:
| • | Component or system operation |
Repair the components as necessary. Refer to Electrical Connections
or Wiring in this table.
|
Electrical Connections or Wiring
|
| • | Intermittents are usually caused by one or more of the following
conditions: |
| - | Poor electrical connections |
| • | Carefully inspect the suspected circuit for the following
conditions: |
| - | Poor mating of the connector halves |
| - | Terminals backed out or 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. |
| - | 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. |
| - | Wires that are broken inside the insulation |
| - | Pinched, cut or rubbed through wiring in the harness |
| - | Wiring that is 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 or component connectors, 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 the ability of a circuit 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 or connection
reaches normal operating temperature. The condition may occur only when the
component or connection is cold, or only when the connection is hot. |
| • | The following data may help to diagnose this type of intermittent
condition: |
| - | Freeze Frame and Failure Records |
| • | If the intermittent is related to heat, review the following data: |
| - | High ambient temperatures |
| - | Underhood or engine generated heat |
| - | Circuit generated heat due to a poor connection, or high electrical
load |
| - | Higher than normal load conditions, such as towing |
| • | If the intermittent is related to cold, review the following data: |
| - | 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 is not present after 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 or circuits are sensitive to
EMI or other types of electrical noise. Perform the following procedures:
| • | Inspect for a misrouted harness that is too close to a high voltage
or high current device. This condition may induce electrical noise on a circuit
that could interfere with normal circuit operation. Inspect
for wires that are too close to the following devices: |
| - | Secondary ignition components |
| • | Determine whether the electrical system interference is caused
by a malfunctioning relay, PCM driven solenoid or switch. These components
may cause a sharp electrical surge. Normally, the problem will
occur when the malfunctioning component is operating. |
| • | Determine whether non-factory or aftermarket add-on accessories
are installed in the vehicle. These accessories may lead to an emission related
OBD II failure. Determine if any of the following non-factory or aftermarket
add-on accessories is causing the intermittent: |
| • | Test for an open diode across the AC compressor clutch and for
other open diodes. Some relays may contain a clamping diode. |
| • | 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. Refer to
Checking Aftermarket Accessories
in Wiring Systems. |
|
Incorrect PCM Programming
|
| • | There are only a few situations when reprogramming a PCM is appropriate,
such as the following: |
| - | 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 re-program the PCM with the SAME software 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 or calibration. If
incorrect programming is found, reprogram the PCM with the most current software
or calibration. Refer to
Powertrain Control Module Programming
. |
|
Duplicating Failure
Conditions
|
| • | If none of the previous tests are successful, attempt to duplicate
or capture the failure conditions. |
| • | Freeze Frame and Failure Records data, where applicable, contains
the conditions that were present when the DTC set. Perform the following procedure: |
| 1. | Review and record Freeze Frame and 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 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. |
| 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.
|
