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
Service Programming System (SPS)
in 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.
|
