Inspection/Test
| Action
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DEFINITION: The condition is not currently present but is indicated in DTC History.
OR
There is a customer concern, but the condition can not currently be duplicated (if the condition is not DTC related).
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Preliminary
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| • | The fault must be present to locate a problem using the DTC table. If
a fault is intermittent, the use of DTC tables may result in the replacement of good
parts. |
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Harness/Connector
| Many intermittent open or shorted circuits come and go with harness/connector movement caused by vibration, engine torque, bumps/rough pavement, etc. Inspect 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 the scan tool. Observe the components 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
and
Connector Repairs
in Wiring Systems.
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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. |
| • | Inspect the harness for pinched, cut or rubbed through wiring. |
| • | Make sure wiring does not come in contact with hot exhaust components. |
Refer to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems.
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PCM Power and Grounds
| Poor power or ground connections can cause widely varying symptoms.
| • | Test all powertrain control module (PCM) power circuits. Many vehicles
have multiple power circuits feeding the PCM. Inspect connections at the PCM
connectors, fuses, and any intermediate connections between the power source and
the PCM. A test lamp or a DMM may indicate that voltage is present, but neither tests
a circuits ability to carry sufficient current. Ensure that the circuit can carry
the current necessary to operate the component. Refer to
Power Distribution Schematics
and
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. |
| • | Test all PCM ground and system ground circuits. The PCM 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
and
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. |
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Temperature Sensitivity
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| • | 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. |
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Electromagnetic
Interference (EMI) and Electrical Noise
| Some electrical components/circuits are sensitive to electromagnetic interference (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, PCM driven
solenoid, or switch. These conditions cause a sharp electrical surge. Normally, the
problem will occur when the malfunctioning component is operating. |
| • | Improper installation of non-factory (aftermarket) add-on accessories
such as lights, 2-way radios, amplifiers, electric motors, etc. |
| • | Test for an open diode across the A/C compressor clutch, and for other
open diodes. |
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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 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 information. If incorrect programming is found, re-program the PCM with the most current software/calibration information. Refer to
Service Programming System (SPS)
in Programming.
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Duplicating Failure Conditions
| If none of the previous inspections 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.
- Review and record Freeze Frame/Failure Records data
- Clear 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 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.
- 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 DMM connected to a suspected circuit. An abnormal reading on the DMM when the problem occurs, may help you locate the problem.
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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.
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