Analyzing Data - Step 10
ANALYZING DATAOnce the road test is completed, the results should be analyzed to locate and service the fault which caused the symptom or Diagnostic Trouble Code (DTC).
INSIGHTS FROM THE RECORDER
- The use of the recorder enhances the view of the EEC operation during the presence of the symptom or DTC and allows 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 relatively stable. Sensors such as TP, MAP and RPM that change abruptly as the vehicle is travelling at a constant speed are clues.
- Look for agreement in related signals. For example, if TP is changed during a gentle acceleration, a corresponding change should occur in MAP, RPM and Timing. Compare signals by selecting different channels at a certain time range.
- Make sure the signals act in proper sequence. An increase in RPM after the TP is increased is expected. However, if the RPM increases without a TP change, a problem may exist.
ANALYZING METHODS
Use any of the following methods to further diagnose a suspected EEC signal or device. Some methods are particular to a certain type of EEC device. Follow the test strategy listed for each type of EEC signal -- Refer to the Methods of EEC Monitor Measurement.
- Change condition to cause response by input
- Change input and verify output response
- Check value
- Click testing (solenoids/relays)
- Coil resistance (solenoids/relays)
- EEC input check
- Harness opens
- Harness shorts
- Output state DTM (solenoids/relays)
- Wiggle testing (DCV or Ohms)
ANALYZING DATA: SUGGESTED STRATEGIES FOR SENSORS/INPUTS
2 Wire Sensors
3 Wire Sensors
Switches
Other Input Signals
ANALYZING DATA: SUGGESTED STRATEGIES FOR ACTUATORS/OUTPUTS
Solenoids/Relays
Other Output Signals
OPTIONAL DIAGNOSTIC TOOLS
By using the suggested strategies for the "suspect" EEC components, the source of the fault can be found. If, after following the given methods a fault is not found, a few options remain.
Follow-up Diagnosis. The monitor and recorder can be used to diagnose EEC signals other than those listed in the chosen symptom chart. By conducting a thorough investigation of all the EEC signals, the source of the problem may be found. Two peripherals are available for auxiliary (AUX) inputs: Auxiliary Adapter (007-00023) and the Pressure/Vacuum Adapter (007-00022).
Other Diagnostic Tools. There are other specialized tools that could aid in diagnosis. The Distributor Tester (007-00075) can be used for electronic ignition systems. If an electronic distributorless ignition is present, special diagnostic tools are needed. Another useful tool is the Fuel Injector Tester/Cleaner Kit (164-R3759) which checks for contaminated fuel.
VERIFICATION
After the vehicle fault has been located and serviced, a verification test should be performed. This may require a road test to verify that the symptom or continuous memory DTC is no longer present. It is also important to remember that if any continuous memory DTCs were present before the symptom was serviced, those DTCs must be cleared.