EEC-IV Testing 

a corral original article 
Christopher Ihara
 
CORRAL UNIVERSAL RATING SYSTEM: 
Difficulty (Easy 1-10 Difficult) Very Easy
Special Tools (Few 1-10 Many) Possibly Some
Price (Cheap 1-10 Expensive) Cheap
Quality (Poor 1-10 High) N/A
Improvement (None 1-10 Alot) N/A
Customer Service (Poor 1-10 Good) N/A

Hidden behind the passenger side kick panel of your Mustang is the core of your car's performance capabilities - the Ford Electronic Engine Control version Four (EEC-IV, pronounced eek-four).  Using a myriad of sensors, the EEC-IV manages all aspects of your engine's operations from cold starting to Wide Open Throttle.  These sensors monitor things like Barometric Pressure, Coolant Temperature, Air Temperature, Exhaust Oxygen content, throttle position, and many other atmospheric and driver input parameters affecting the engine's performance. 

One of the many other capabilities of the EEC-IV is its ability to diagnose a poorly running engine.  Through the use of self-contained sensor tests the EEC-IV can provide information about failed sensors, or sensors picking up abnormal operating conditions which can cause your car to perform poorly.  In addition to these tests, the EEC-IV can also perform cylinder balance checks informing you of individual cylinders which may be experiencing a drop in compression. 

This information is stored in the form of numeric codes.  The 5.0 Liter Mustang's EEC-IV has the ability to record and store data from up to 80 start-up cycles in its memory.  Additionally the EEC-IV runs a continuous self-test during normal operation, and errors detected will be stored in the EEC's Keep Alive Memory, or KAM.  These codes can then be extracted from the KAM for diagnosis later.  The codes are referred to as "Continuous Memory Codes" and are stored in the KAM until they are overwritten or the EEC-IV loses power for more than 10 minutes. When these codes are downloaded from the KAM, they will be displayed in a "morse-code" like fashion.  The EEC-IV emits pulses to represent these numeric codes; for example, two pulses, a short pause, then four more pulses would signal a code 24. 

The EEC-IV has two different test modes, the first mode is called Key On Engine Off, or KOEO. The second mode is called Key On Engine Running, or KOER, and each mode has a specific purpose.  The first mode KOEO is designed to test all the sensors and ensure that they are functioning within their parameters.  The KOEO mode will also display any startup error codes stored in the KAM.  The KOER mode is designed to analyse the engine while it is running.  Any sensors that detect abnormal engine functionality or that are operating out of specification will generate error codes.  During KOER it is also possible to perform additional tests like the cylinder balance test. 

To properly diagnose any problems with your car you must first ensure that all vacuum hoses, connectors, and sensors are properly connected.  Vacuum leaks, missing sensors, corroded, loose, or unplugged connectors will cause diagnosis problems and should be corrected before continuing. 

When you have finished correcting any visible problems you may now begin testing the EEC-IV. These codes may then be extracted using one of three different methods. By connecting to the EEC-IV test wiring harness and the Self-Test Input connector you can extract codes using an analog volt-meter, the car's "Check Engine" light, or a commercial code scanner. 

Regardless of the method you use to perform EEC-IV diagnostics you will always need to peform the following steps.  

  1. First ensure that the vehicle is turned off.
  2. Fix or replace any disconnected, loose, or missing sensor connections, sensors, or vacuum hoses.
  3. Jumper the connection between the EEC-IV test harness and the Self-Test Input connector. 
Method One - Analog Volt Meter 
Using an analog volt meter is perhaps one of the most popular ways to test the EEC-IV. It requires very few special tools and is quite simple to accomplish. 
 
TOOLS SECTION - Method One 
  • Analog Volt Meter
  • Wire Cutters
  • Wire Crimpers
  • 5 feet of red 12 Gauge wire 
  • 2 feet of black 12 gauge wire
  • 4 inches of black 12 gauge wire
  • (3) Three 1/4" Crimp On Male Blade Plugs
  • (2) Two Crimp On Alligator Clips
  • To use an analog volt meter you will need to connect to the positive battery terminal to the positive lead on your volt meter.  You will then connect the negative lead of the volt meter to the EEC-IV test harness as shown. Finally you will jumper the Signal Test Input (STI) into the EEC-IV test harness. 

    The next few steps are optional, but they will help make testing your EEC-IV much easier.  We're going to make three wire leads that will simplify our test procedures by allowing us to perform all necessary diagnostics from within the car.  The first thing we'll need is a power lead from the battery to the volt meter, the next is a lead from the EEC-IV harness to the volt meter, and finally we'll need a jumper lead from the STI to the EEC-IV test harness. 

    To make the power lead we will need a five foot section of our red 12 gauge wire. Strip about 1/2 inch of insulation from  both ends of the wire and crimp an alligator clip onto either end. 

    For the ground lead we will need a two foot section of black 12 gauge wire.  Strip about 1/2 inch of insulation from both ends of the wire and crimp an alligator clip to one end and a 1/4" male blade connector on the other. 

    Finally for the STI wire we will use a four inch section of black 12 gauge wire.  Strip about 1/2 inch of insulation from both ends of the wire and crimp a 1/4" male blade connector onto either end. 

    These extra wires will enable us to connect the volt meter to all necessary circuit points and still work from within the vehicle.  This is particularly handy as the EEC-IV does require some input from vehicle controls like the brake pedal and steering wheel. 

    With the vehicle off, connect the ground lead to the volt meter using the alligator clip and the other end to the EEC-IV test harness using the 1/4" blade connector.  Next, jumper the STI and the EEC-IV test harness using the four inch connector.  Finally, connect the power lead to the volt meter, then to the positive terminal on the battery.  Be very careful not to let the power lead touch anything metal within  the car!  This will ground the circuit and will cause a spark! 

    To read the codes output by the EEC-IV on your volt meter you will count the number of times the needle sweeps from about 0 volts to 5 volts.  Each sweep of the needle is one pulse from the EEC-IV.  For example if the volt meter were to sweep six times, then pause for one half second, then sweep six more times this would indicate an error code 66.  An error code 66 indicates that no mass air flow signal is present. 

    Now continue on to the KOEO Testing Procedures section. 

    Method Two - Check Engine Light 
    One of the easiest ways to test the EEC-IV is to use the check engine light in the instrument cluster. This method is particularly handy because it requires no special tools and only a small jumper wire to perform the test. For simplicity's sake we will make our own jumper wire that you can store in your glove compartment.  
     

    TOOLS SECTION - Method Two 
  • Wire Cutters
  • Wire Crimpers
  • 4 inches of black 12 gauge wire
  • (2) Two 1/4" Crimp On Male Blade Plugs

  •  
    First, cut a four inch section of black 12 gauge wire and strip 1/4" from each end.  Next crimp a 1/4" male blade plug onto either end. 

    To read the codes output by the EEC-IV on your Check Engine light you will count the number of times the light flashes.  Each flash of the Check Engine light is one pulse from the EEC-IV.  For example if the light were to flash six times, then pause for one half second, then flash six more times this would indicate an error code 66.  An error code 66 indicates that no mass air flow signal is present. 

    Now continue on to the KOEO Testing Procedures section. 

    Method Three - Commercial Code Scanner 
    Perhaps the easiest way to read codes is to purchase a readily available scanner made by companies like Actron. Many companies make EEC-IV scanners, some ranging in price from as little as $30 to several hundred dollars depending on their complexity and features.  Ford's STAR tester sells for several hundred dollars and has scanning, data logging, and other capabilities better suited to professional mechanics. 

    Actron's EEC-IV code scanner sells for around $30 at your local auto parts store and comes with complete instructions and code listings.  You simply plug the code scanner into the EEC-IV test connector and the EEC-IV test connector's ground.  That is all that needs to be done to set up the EEC-IV for testing using a commercial code scanner. 

    To read the codes output by the EEC-IV on your code scanner you will count the number of times the scanner's LED flashes, or the number of beeps you hear (depending on how you have your scanner configured).  Each flash of the LED (or beep from the scanner) is one pulse from the EEC-IV.  For example if the LED were to flash six times, then pause for one half second, then flash six more times this would indicate an error code 66.  An error code 66 indicates that no mass air flow signal is present. 

    Now continue on to the KOEO Testing Procedures section. 

     
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