Step 5: Analyzing Data

Analyzing Data

Once the road test is completed, the results need to be analyzed to find and repair the exact fault which caused the symptom. The recorded data and notes taken during the road test can now be analyzed, discussed and compared with Appendix data.

Insights from the RECORDER

Recording data greatly enhances the view of the EEC operation during the presence of the symptom and allows a systems approach to the problem. By selecting VIEW RECORDER DATA - NUMERICAL or GRAPHICAL, and playing back the data, you can begin to evaluate the results.

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 Throttle Position (TP) and Mass Air Flow (MAF) changing abruptly when the vehicle was travelling at a constant speed are clues.

Look for agreement in related signals. For example, if the TP is changed during a gentle acceleration a corresponding change should occur in MAF. Compare the signals by selecting different signals at a certain time range.

Make sure the signals act in proper sequence. An increase in RPM after the TP is increased is valid. However, if the RPM increases without a TP change then a problem exists.

Analyzing Methods

Use any of the following methods to further troubleshoot a suspected PCM signal. Some methods are unique to a certain type of PCM device. Follow the given strategy listed for each unique device.

- 2 Wire Sensors: 2 Wire Sensors
- 3 Wire Sensors: 3 Wire Sensors
- Switches: Switches
- Other Input Signals: Other Input Signals
- Solenoids/Relays: Solenoids/Relays
- Other Output Signals: Other Output Signals


Follow-up Diagnosis

By using the suggested strategies for the "suspect" PCM components, the source of the fault can be found. If a fault is not found, refer to the Diagnostic Routines. This section lists various symptoms and references possible systems. Symptom Related Diagnostic Procedures

Verification

After the vehicle fault has been located and repaired, a verification test needs to be performed. This may require a road test to verify that the symptom is no longer present. It is also important to remember that if any diagnostic trouble codes were present before the symptom was repaired, those codes must be cleared.