Appendix:Diagnostic Aids
198924-01-95 Fuel System Diagnosis 24-01-95
APPENDIX: Diagnostic Aids
CONTINUOUS MONITOR TEST (WIGGLE TEST)
This test is intended as an aid in diagnosing intermittent failures in the sensor input and output circuits.
Connect a VOM/STAR to the self-test output.
Key On Engine Off Continuous Monitor Test, (Wiggle Test).
To enter this mode, turn the key to ON. Self-test output will be activated whenever a continuous fault is detected and if the duration is long enough, a fault code will be indicated.
Engine Running Continuous Monitor Test, (Wiggle Test).
The Continuous Monitor (Wiggle) Test will allow the technician to enter this mode of Self-Test and to attempt to re-create the intermittent failure tap, move, wiggle the harness and/or the suspected sensor.
If the VOM/STAR indicates a fault (short or open) the corresponding service code will be indicated. Now with the knowledge of the affected circuits, a close check of the harness and associated connectors can be made.
NOTE: Remember to keep your eyes on the VOM/STAR for any change which will indicate where the intermittent is located.
EXAMPLE: How to Use the Continuous Monitor Test (Systematically)
If a service code 09 was displayed: Engine Coolant Temperature Sensor:
^ Visually inspect the sensor very closely.
^ Enter Continuous Monitor Test.
^ Lightly TAP on the sensor.
^ Push/pull on the sensor harness connector (do not disconnect, yet).
^ Test and wiggle (shake) harness vigorously working from the sensor connector toward the dash panel and from the dash panel to the processor in short sections.
^ If VOM has not given a positive indication of an intermittent, disconnect the sensor from the harness as carefully as possible. Remove terminals from the connector. Visually inspect terminals at both ends for corrosion, bad crimps, improperly seated terminals, etc.
^ Reconnect after inspection.
^ Disconnect processor from harness as carefully as possible.
^ Inspect terminals.
^ Only remove terminals associated with the sensor being inspected.
^ If the VOM does not give a positive intermittent indication, reconnect the connector and erase the Continuous Test service codes.
^ To erase the continuous memory service codes:
- Disconnect negative battery cable and depress brake pedal for 5-10 seconds.
- Repeat Self-Test to verify service codes have been erased.
1989
24-01-96 Fuel System Diagnosis 24-01-96
APPENDIX: Diagnostic Aids
FAILURE MODE EFFECTS MANAGEMENT (FMEM)
DESCRIPTION
FMEM is an alternate system strategy in the ECA designed to allow improved vehicle drive should one or more sensor inputs fail.
When a sensor input is perceived to be out-of-limits by the ECA, an alternative strategy will be initiated.
The ECA will substitute a fixed in-limit sensor value and will continue to monitor the faulty sensor input. If the faulty sensor operates within limits, the ECA will return to the normal engine running strategy.
MIL "Check Engine" light will remain on when FMEM, is in effect.
1989
24-01-101 Fuel System Diagnosis 24-01-101
APPENDIX: Diagnostic Aids
"CHECK ENGINE" LIGHT (MALFUNCTION INDICATOR LIGHT)
DESCRIPTION
The "Check Engine" light is intended to alert the driver of certain malfunctions in the engine control system.
If such a fault occurs, the processor will substitute a value or values and continue operating. This process is called Failure Mode Effects Management (FMEM). In some cases this action may result in a slight change in driveability.
HOW "CHECK ENGINE" LIGHT OPERATES
System OK
The "Check Engine" light will remain on while the key is in RUN position.
Once the vehicle has started the "Check Engine" light will go out.
System Not OK
If the "Check Engine" light should remain on after the vehicle has started, run Key On Engine Off SelfTest to completion. If the light continues to remain on, go to Pinpoint Test ML.
If the "Check Engine" light never comes on, go to Pinpoint Test ML.
If the driver notices the "Check Engine" light came on for a period then went off, and a service code is present, the code is a continuous code.
The "Check Engine" light only warns the driver of an input device malfunction.
NOTE: When in Self-Test the "Check Engine" light will also flash the service codes.