Checks
| Action
|
DEFINITION: The
problem may or may not turn on the MIL or store a DTC. If a DTC was stored
and the DTC diagnostic table indicates the fault is not present, an Intermittent
Condition is indicated.
|
Preliminary Checks
| Refer to Important Preliminary Checks in
Symptoms - Engine Controls
.
|
Electrical Connections or Wiring
| Electrical connections and
wiring cause most intermittent conditions.
Determine which circuit is suspected of having an intermittent condition.
This may be indicated by DTCs with a fault not present.
Check the suspect circuit for the following conditions:
| • | Connectors that are poorly mated |
| • | Terminals that are not fully seated in the connector |
| • | Terminals that are not properly formed or damaged. This may be
due to improper diagnostic probing procedures. |
| • | Poor terminal retention or male-to-female connection |
| | Checking for proper terminal retention requires the use of the J-38125
Terminal Repair Kit. |
| • | Poor terminal-to-wire connections |
| • | Wires that are broken inside the insulation |
| • | Pierced or damaged insulation that allows water or 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
circuit. |
Refer to
Wiring Repairs
and to
Connector Repairs
in Wiring Systems for the proper
procedures to use when making a circuit repair.
|
Road Test
| The following tests should
be performed with 2 people in order to ensure the safe operation of the vehicle.
| • | Drive the vehicle while monitoring the suspect circuit with a
scan tool or a DMM connected to the circuit. Look for an abnormal reading
or voltage when the malfunction occurs. An abnormal reading on the scan
tool or an abnormal voltage on the DMM display is an indication that
there may be a malfunction in the circuit that is being monitored. |
| • | If the intermittent fault sets a DTC, the diagnostic that sets
the DTC can be monitored on the scan tool under the Not Ran Since Code Cleared
selection in the DTC Information menu. If the DTC appears in the Not
Ran Since Code Cleared list, the DTC diagnostic has not yet run. When
the DTC does not appear in the Not Ran Since Code Cleared list, the DTC
diagnostic has run. If the MIL is NOT illuminated and there is no Pending
DTC Status in DTC Information, the DTC diagnostic has passed. DTCs MUST
be cleared in order to view the Current Status of the Not Ran Since
Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared
list only indicates that the test has run, not whether the test passed
or failed. The DTC Information screen must be checked for CURRENT or
PENDING status, in order to determine the outcome of the diagnostic
test involved. |
|
Scan Tool
| The scan tool features that can be used to
locate an intermittent conditions include the following:
| • | The scan tool snapshot feature |
| | The scan tool snapshot feature can be triggered to capture and store
the engine parameters when a malfunction occurs. This stored information can
be reviewed and compared to the Typical Scan Tool Data Values or
to data values taken from a similarly equipped, known-good vehicle. |
| • | The Freeze Frame and Failure Records data feature |
| | The Freeze Frame and Failure Records are stored when certain DTCs set.
The Freeze Frame and Failure Records typically include information to aid
in reproducing the driving conditions that were present when a DTC
is stored. In addition, the engine parameters are also stored. This
stored information can be reviewed and compared to the typical
Scan Tool Data List
values or to data values
taken from a similarly equipped, known-good vehicle. |
| | The Freeze Frame and Failure Records data will be erased when the DTC
Information is cleared either by scan tool clearing or by disconnection of
the control module's power supply. |
|
Intermittent
Malfunction Indicator Lamp (MIL)
| The following conditions may cause intermittent MIL operation
with no DTCs stored:
| • | A defective relay, control module driven solenoid, or a switch
that causes electrical system interference. Usually the symptom will occur
when the faulty component is operating. |
| • | Any ignition control (IC) wires routed near the generator or near
secondary ignition system wires and components |
| • | An ignition system secondary voltage that is shorted to ground |
| • | Inadequate ignition control circuit grounds |
| • | The malfunction indicator lamp (MIL) control circuit intermittently
shorted to ground |
| • | Any faulty diodes in the generator or charging system circuits |
| • | The improper installation of add-on electrical devices including
the following: |
|
Loss of DTC Memory
| In order to check for proper DTC Memory function, perform the following
procedure:
- Observe the Conditions For Running the DTC for the throttle position
(TP) Sensor Circuit Low Voltage DTC.
- Disconnect the throttle position (TP) sensor connector.
- Operate the vehicle within the Conditions For Running the DTC.
- The MIL should illuminate upon completion of all the Conditions
For Running the DTC. Two key cycles or drive trips may be required.
- A TP Sensor Circuit Low Voltage DTC should be stored in the PCM
and remain in memory when the ignition is turned Off.
The failure to store a DTC or failure of the DTC to remain in memory
may indicate a faulty PCM.
|
Additional Checks
|
| • | Check for open diodes that may cause electrical interference. |
| • | If the intermittent fault is suspected to involve a particular
sensor or component, observe the sensor or component display on a scan tool
while moving the connectors and the wiring harnesses related to the sensor
or component. A change in the scan tool display can indicate the location
of the fault. |
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