Checks
| Action
|
DEFINITION: The problem may or may not turn ON the MIL
or store a DTC. There is a customer concern, but the symptom can not currently
be duplicated, or the DTC diagnostic table indicates the fault not present
at this time.
|
Preliminary Checks
|
| • | Refer to Important Preliminary Checks in
Symptoms
. |
| • | The fault must be present in order to be diagnosed correctly with
a DTC table. If the fault that set the DTC is intermittent, then the use of
DTC tables may result in replacement of good parts. |
|
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:
| • | Any connectors that are poorly mated. |
| • | Any terminals that are not fully seated in the connector. |
| • | Any terminals that are not properly formed or damaged. |
| • | A poor male to female connection |
| | Checking for proper terminal retention requires the use of the J-38125
Terminal Repair Kit. |
| • | Any poor terminal-to-wire connections |
| • | Any wires that are broken inside the insulation. |
| • | A 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 digital multimeter (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 multimeter display
is an indication that there may be a malfunction in the circuit that
was 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
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/Failure Records data feature |
| | The Freeze Frame/Failure Records are stored when certain DTCs set. They
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
Engine Scan Tool Data List
values or to data values taken from a similarly equipped
known-good vehicle. |
| | The Freeze Frame/Failure Records data will be erased when DTC Information
is cleared either with the scan tool or by disconnection of the control
modules' (ECU, VCM/PCM or ECM) 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
the secondary ignition system wires and components. |
| • | An ignition system secondary voltage that is arcing and shorting
to ground. |
| • | Any poor ignition control circuit or ignition module grounds. |
| • | A MIL control circuit that is intermittently shorting to ground. |
| • | Any faulty diodes in the generator or charging system circuits. |
| • | The improper installation of add-on electrical devices. These
can include 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 TP Sensor Circuit
Low Voltage DTC.
- Disconnect the 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.
A 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 (A/C clutch, charging system, etc.) that
may cause electrical interference. |
| • | The improper installation of add-on electrical devices. These
can include the following: |
| • | If the intermittent fault is believed 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 the component. A change in the scan tool display can indicate the
location of the fault. |
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