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 - Engine Controls
, 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 connections:
| • | 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 conditions:
| • | Any high ambient temperatures |
| • | Any underhood, engine generated heat |
| • | Any circuit generated heat due to a poor connection or a high
electrical load |
| • | Any igher than normal load conditions such as towing, etc. |
If the intermittent is related to cold, review the data for the following
conditions:
| • | 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 and/or 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. |
|
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
.
|
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 the 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 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 is connected to the data link
connector (DLC) and sent with the customer. The J 42598
captures data for later retreival and analysis by the technician.
Refer to the J 42598
user instructions for more information.
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