EEC Self Test Procedure

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Adapted for the Taurus SHO from "EEC-IV Self Test Procedure Article" by Scott Griffith. Mr. Griffith's article deals with the Mustang, so this adaptation may be somewhat incorrect and incomplete for the SHO application.

Recommended reading:

  • Engine and Emissions Diagnosis Manual, available from Helm, Inc.
  • Probst, Charles, How to Understand, Service, and Modify Ford Fuel Injection and Electronic Engine Control, Robert Bentley, Cambridge, MA, ISBN 0-8376-0301-3

Procedure for EEC-IV Quick Tests

There are two tests in the EEC-IV Quick Tests: Key-On, Engine Off (KOEO) and Key-On, Engine Running (KOER). Before running the test, you must establish these conditions:

  • Engine warmed up to normal operating temperature
  • Transmission in neutral
  • Heater and air conditioning off

To run the tests, you must locate the EEC-IV test connectors. In the '89-'95 Taurus SHO, these are in the engine compartment, right between the intake manifold and the firewall, next to the passenger-side strut tower. There are two connectors of interest: one is a 6-pin connector, and the other is a single pin connector. They may be stuck into a single grey plastic hood embossed with "EEC Test". The connectors use 1/4" quick disconnect-style terminals, so you'll probably want to make yourself a jumper about 8" long with a 1/4" male QD terminal on each end, if you mean to do this often. Otherwise, any random chunk of wire will do.


The graphic shows the pinout for the EEC-IV connector, looking at it from the working side (looking into the female terminals). Only the three pins denoted may actually have terminals in them- the other positions may be empty.

The single terminal hanging loose is the Self Test Input pin (STI). To run the test, you just watch your Check Engine light. Alternatively, you can hook up an analog voltmeter between the positive terminal of the battery, and the Self Test Out (STO) pin; you'll count its needle sweeps to read the codes. The Fuel Pump (FP) test pin, when grounded, runs the fuel pump continuously- but that's just FYI. You won't deal with that pin for these tests.


Jumper the STI pin and the Signal Return pin. Turn the ignition to "Run", but do not crank the starter. The KOEO test will begin. During this test, these things will happen:

  • EEC will exercise its valves and actuators and take readings from its sensors
  • The EEC will flash the Check Engine light to indicate any KOEO on-demand codes it has found at the moment of the test. All codes are presented in sequence twice.
  • The EEC will flash the Check Engine light once to give a separator code.
  • The EEC will flash the Check Engine light to indicate any continuous codes stored in non-volatile memory during operation prior to the test.


Set up as mentioned above, but start the car and run it at 2000 rpm for a couple of minutes. This thoroughly warms up the oxygen sensors. Shut down, jumper the STI and Signal Return pins, and immediately restart the car. The KOER test will begin. During this test these things will happen:

  • You will get the engine ID code on the Check Engine light (3 pulses for 6 cylinders).
  • The EEC will try to get its sensors to go to the extremes of their ranges. The car will run very poorly at times during this portion of the test. It lasts for 6 to 20 seconds.
  • The motor will smooth out and idle. You will see a single flash of the Check Engine light.
  • After this flash, you have 10 seconds to turn the wheel both ways, hit the brake, and snap the throttle wide open, release the throttle, and let the engine return to idle. This is called the "goose test". If you have an automatic, you should also turn the overdrive on and off during this phase of the test.
  • The EEC will flash the Check Engine light to indicate any KOER on-demand codes it has found at the moment of the test. All codes are presented in sequence twice. If you didn't run the goose test right, it will flash 77 and you will repeat the goose test.
  • After the KOER test completes you can optionally run the SEFI or Cylinder Balance test. Raise the throttle to around 2,500 RPM and release it. The computer elevates the idle to around 1800 RPM, and then will cut the injector to each cylinder looking for an expected drop in RPM. No drop means a problem with that cylinder. As each cylinder is taken offline, you won't see much movement in the tachometer, but the engine will feel rougher, out of balance. When the cylinder comes back online, the engine will feel normal again. A code of 1-6 identifies a cylinder found to be weak. A code of 9 means all OK. As with other tests, the codes are shown twice.

Clearing Continuous Codes

To clear continuous codes, disconnect and then reconnect your jumper while the continuous codes are being displayed.

Interpreting Codes

The DTC codes provided changed through the evolution of the Taurus ECU, with the earlier V6 models (i.e. first-generation: 1989-1991) using 2-digit codes, and the later V6 models (i.e. second-generation: 1992-1995) using 3-digit codes.
Template:Note 1996-1999 models follow the OBD-II standard, so they use 4-digit codes beginning with a letter "P".

1989-1991 Two-digit EEC codes
1992-1995 Three-digit EEC codes
1996-1999 Four-digit "P"-prefix EEC codes

Aftermarket Testers


An aftermarket tester is available from SunPro for $35-$40. It is available at most large auto parts chains. It is really nothing more than a nice connector, a light, and a speaker you read just like the Check Engine light, and it comes with a list of codes.


The Equus model 07-4977 will read 2 and 3 digit codes. It has a memory that will hold 12 codes. It tells you whether the code is KOEO, KOER, CM (continuous code) or CYL (cylinder code). It takes 2 'AA' batteries and has a low battery indicator. The instruction book tells you how it all works, how to perform each test and includes 2 and 3 digit code lists. The codes stay in memory as long as the batteries have juice. You can also erase codes in the EEC system with the reader, instead of disconnecting the car's battery.

JCWhitney had it priced recently at $59.95, and Great(er?) Northern Equipment had it in their catalog (apparently the same type/manufacturer) for around $47.00. Summit Racing lists it in their catalog for $49.00.

There is an extension cable sold separately for $20.00 that will allow you to sit in the car and operate the reader. You don't have to get in and out turning the ignition and the reader on/off. You can also turn the wheel and step on the brake at the right time.

I can't find my EEC test connector!

If you can't find the EEC test connector, it may be lying below decks on one of the catalytic converters. If this is the case, it's probably a useless melted blob. Purchase a replacement connector from Ford (about $16).