Checks
| 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 Inspection
| Refer to
Symptoms
, Important Preliminary
Checks Before Starting.
|
Harness and Connector
| Many intermittent
open or shorted circuits come and go with harness or 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 the related connectors and the wiring while monitoring the
appropriate scan tool data. |
| • | Move the related connectors and the wiring with the component
commanded on and off with the scan tool. Observe the component's operation. |
| • | With the engine running, move the related connectors and the wiring
while monitoring the engine operation. |
If a harness or connector movement affects the data displayed, the component
or system operation, or the engine operation, inspect and repair the harness
and connections as necessary.
Refer to Electrical Connections or Wiring in this table.
|
Electrical Connections and Wiring
| Poor electrical connections and 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 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. |
| • | Make sure the wiring does not come in contact with hot exhaust
components. |
Refer to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems.
|
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 or 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 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 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 a normal operating temperature. The condition
may occur only when the component or connection is cold, or only when the
component or connection is hot.
The Freeze Frame, the Failure Records, the Snapshot, and the 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:
| • | Any high ambient temperatures |
| • | Any underhood, engine generated heat |
| • | Any circuit generated heat due to a poor connection or a high
electrical load. |
| • | Any higher than normal load conditions such as towing, etc. |
If the intermittent is related to cold, review the data for the following:
| • | Any low ambient temperatures. In extremely low temperatures, ice
may form in a connection or component. Check 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 or high
current devices such as the secondary ignition components, the motors, the
generator, etc. These components may induce electrical noise on
a circuit that could interfere with normal circuit operation. |
| • | Any electrical system interference caused by a malfunctioning
relay, a PCM driven solenoid, or a switch. This can cause a sharp electrical
surge. Normally, the problem will occur when the malfunctioning component
is operating. |
| • | The improper installation of aftermarket add on accessories such
as lights, 2-way radios, amplifiers, electric motors, remote starters, alarm
systems, cell phones, etc. |
| • | Test for an open diode across the A/C compressor clutch and
for other open diodes. Some relays may contain a clamping diode. |
| • | Test the generator for a bad rectifier bridge that may be allowing
AC noise into the electrical system. Refer to
Diagnostic Starting Point
in Engine Electrical. |
|
Incorrect PCM Programming
| There are only a few situations where reprogramming
a PCM is appropriate:
| • | When a new service PCM is installed |
| • | When a PCM from another vehicle is installed |
| • | When revised software or calibration files have been released
for this vehicle |
Important:: DO NOT re-program the PCM with the same software and 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 calibration. If
incorrect programming is found, re-program the PCM with the most current software
or calibration. Refer to
Powertrain Control Module Replacement/Programming
.
|
Duplicating Failure Conditions
| If none of the previous checks
are successful, attempt to duplicate and/or capture the Failure Conditions.
The Freeze Frame and Failure Records data contains the conditions that
were present when the DTC set.
- Review and record the Freeze Frame and Failure Records data.
- Clear any DTCs using the scan tool.
- Turn the key to Off and wait 15 seconds.
- Operate the vehicle under the same conditions that were noted
in the 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.
- 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 a digital multimeter
(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 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 Vehicle Data Recorder J 42598
is connected to the
DLC and sent with the customer. The Vehicle Data Recorder captures data for
later retrieval and analysis by the technician. Refer to the Vehicle Data
Recorder user instructions for more information.
|
