EEC Intermittent Fault Diagnosis Introduction

Defining Intermittent Driveability Symptoms

The Rotunda NGS Scan Tool 007-0050015 a useful tool for diagnosing intermittent driveability symptoms which are unable to be resolved through the diagnostics in Pinpoint Tests. This section supports diagnostic procedures and data using the NGS Scan Tool's DATA MONITOR AND RECORD function in a symptom-oriented manner. Also, ACTIVE TEST function is used for Click Testing and Output State Check.

By definition, an "intermittent" symptom is a randomly-occurring drive symptom for which no hard codes are revealed by the NGS Scan Tool's DIAGNOSTIC TEST MODE RESULTS. The Quick Test often results in pass codes while the drive symptom still exists.

Before proceeding with the following procedure, be sure that:

- Customary mechanical system tests and inspections reveal nothing. (Remember, mechanical component problems can make a good EEC system react abnormally.)
- EEC Quick Test and associated EEC Pinpoint Test diagnostics have been completed, but the symptom is still occurring.
- Review of Ford Technical Service Bulletins (TSBs) and inquiry into On-line Automotive Service Information System (OASIS) turn-up no applicable articles.

Purpose of This Section

The NGS Scan Tool's DATA MONITOR AND RECORD function acts as a "window" into the EEC system. Through this "window" the user is able to view the same sensor and actuator values the PCM uses to make decisions about engine performance. The DATA MONITOR AND RECORD function displays these values for both static (KOEO) and dynamic conditions (KOER). The advantage of the RECORD function is the ability to take a "snapshot" of selected PCM signals which can be stored and reviewed later.

A basic working knowledge of the EEC system is critical to efficient troubleshooting of the symptom. No diagnostic procedure can account for all the possibilities which can be encountered, therefore this diagnostic procedure only attempts to provide basic steps and methods for isolating possible causes.

The diagnostic procedure used in this section is a symptom-based approach for isolating the faulty system, circuit or sensor. Often a mechanical fault will cause a good EEC system to react abnormally. In those cases, the use of DATA MONITOR AND RECORD function with this diagnostic procedure will help to eliminate possible EEC faults and also locate mechanical faults.

Questions/Information

In order for a vehicle to be correctly diagnosed, it is important to obtain accurate information about the vehicle and the intermittent symptom. Consider the following points and questions:

- Get a full description of the vehicle operating conditions when the symptom occurs - details such as range of speed, engine hot or cold, accelerating or decelerating, heater or A/C on, engine noise, etc.
- Did the symptom occur gradually or all of a sudden?
- Could it be related to a previous event - such as an accident or part replacement?
- What is the service history? Has it been serviced in the past in a way that might relate to the present symptom?
- Could the problem be related to the customer's driving habits, improper maintenance or neglect, or use of improper or poor fuels?