Analyzing Methods

TWO AND THREE WIRE SENSORS

2 And 3 Wire Sensors:

SWITCHES AND OTHER INPUT SIGNALS

Switches And Other Input Signals:

SOLENOIDS/RELAYS AND OTHER OUTPUT SIGNALS

Solenoids/Relays And Other Output Signals:

ANALYZING DATA
Once the road test is completed, the results need to be analyzed to find and correct the exact fault that caused the problem.

INSIGHTS FROM THE RECORDER
The use of the recorder greatly enhances the view of the EEC operation when the fault occurs and allows for a systems approach to the problem. Look for abnormal behavior or values that are clearly incorrect. Inspect the signals for abrupt or unexpected changes. For example, during a steady cruise, most of the sensor values should be fairly stable. Signals such as the Throttle Position (TP), Manifold Absolute Pressure (MAP), and engine rpm changing abruptly during a steady cruise are clues to correcting the problem. Look for agreement in related signals. For example, if the TP signal changes during gentle acceleration, a corresponding change should occur in MAP, rpm, and ignition timing signals. Make sure that the signals act in proper sequence. An increase in rpm after the TP signal is increased is expected. However, if the rpm increases without a TP signal change, then a problem may exist.

ANALYZING METHODS
Use any of the following methods to further diagnose a suspected EEC signal or device. Some methods pertain to a certain type of EEC device. Follow the given strategy listed for each type of EEC signal listed in EEC-IV Monitor Measurement Methods. EEC-IV Monitor Measurement Methods

- Change condition to cause response by input

- Change input and verify output response

- Click testing (solenoids/relays)

- Coil resistance (solenoids/relays)

- EEC input/output check

- Harness continuity

- Harness shorts

- Output state check (solenoids/relays)

- Wiggle testing (DCV or OHMS)