North American Turbocoupe Organization

Retrieving EEC Diagnostic Codes
andrewjs18 Offline
Retrieving EEC Diagnostic Codes
by Jeff Korn

Retrieving the EEC diagnostic codes can be done with a Ford EEC IV “flashing light” code scanner available at most auto parts stores for about $30 to $40, but you can retrieve the codes without buying a code scanner. This can be done by using a jumper wire and your check engine light, if your car has one, or a jumper wire and an analog voltmeter or 12 Volt Light Emitting Diode (LED) available from Radio Shack for under $2. The least desirable way to run the test is to use a voltmeter, as it can be difficult to count out the code pulses by watching the needle on the meter swing. You can also build a dedicated code scanner to run the codes from inside the car for under $5 in parts.  This code scanner is described in another tech article here on the NATO site.

The EEC diagnostic code scan consists of two different tests, called the Key On Engine Off  (KOEO) and the Key On Engine Running (KOER) tests. The KOEO test consists of two different test sections. The first section will identify current faults, and the second section, called the continuous memory test, which gives stored codes for intermittent faults.  After the KOEO codes are outputted, the EEC enters the output state test / wiggle test mode, which allows you to activate / deactivate all the EEC activators (IAB, EVR solenoid, etc), and look for intermittent wiring and sensor faults. The KOER test also enters the wiggle test mode after the codes have been outputted. The code scanner is connected in the same way for both the KOEO and KOER test.

Hooking up the code scanner

Before running any tests, be sure the car has been warmed to operating temperature.

If you have a commercial code scanner, locate the EEC TEST connector and the single terminal self test input (STI) connector under the hood. On Turbo Coupes, this connector is at the front of the drivers side strut tower. Plug in the code scanner according to the manufacturers directions.

If you want to use a jumper wire and analog voltmeter, or jumper wire and 12 Volt LED, locate the EEC TEST connector and STI connector under the hood.  Refer to the figure below that shows how to hook up the jumper wire and the 12 V LED.  If using an analog voltmeter, replace the LED with the voltmeter.  Do not hook up the jumper wire yet!!

If your car has an operating check engine light (CEL), all you need is the jumper wire, and the CEL will flash out the codes.


Running the KOEO test

With the motor at operating temperature, turn the key to the run. Insert the jumper wire.  You may hear some clicking as some relays operate for a few seconds. After a few seconds, the two digit codes will begin flashing on the CEL or LED, or if using a voltmeter, the needle will begin swinging between zero and 12 volts. If the system passes the current fault test, it will flash once for about ½ second, and once for ½ second one second later. A few seconds later, it will repeat the “code 11”.  If the current fault test fails, it will flash a code or codes for the fault or faults. For example, if the EEC senses the throttle position sensor fault, it will flash twice, and then three times (code 23) and then repeat the code 23.

About 10 to 15 seconds after the current fault codes are outputted, a single flash will be seen.  This is called the separator pulse, and separates the current fault part of the test from the continuous memory intermittent fault part of the test.  About 10 to 15 seconds after the separator flash, the continuous memory codes will be outputted in the same way as in the current fault test.  These codes indicate that the EEC detected an intermittent fault in some system.  To erase the continuous code memory  codes, rerun the KOEO test, and disconnect the jumper wire or disconnect the STI connector from the commercial code scanner while the codes are being outputted.

The wiggle test and output state test

If the scanner is left hooked up for roughly two minutes after the last code has been outputted, the wiggle test mode will become active.  In this test mode, you can wiggle the wiring harness, tap on various sensors, etc to look for an intermittent fault.  If an intermittent fault is detected, the scanner will momentarily light up, and if the intermittent fault lasts long enough, the EEC will store a fault code in the continuous memory.

The activators can be tested for operation using the output state test. After the last code is outputted, briefly floor the gas pedal, and then release. The light on the scanner will stay lighted, and all the activators will turn on .  Another brief wide open throttle will turn off the light on the scanner, and will turn off all the activators. This on / off process can be repeated as many times as needed.

Running the KOER test

If you have the scanner or jumper connected, remove the jumper, or disconnect the STI from the scanner.  Start the car, and run it for several minutes to be sure the motor is at operating temperature, and to warm the oxygen sensor to operating temperature. Insert the jumper wire or connect the code scanner.  The motor will rev up, idle down, and do all sorts of strange things.  Soon after starting the test, the engine ID code will flash. This code is ½ the number of cylinders, so on a Turbo Coupe, two flashes will be seen.  After a while, the idle will settle down, and a single flash will be seen. This is the Dynamic Response Code.  When this flash is seen, tap the brake to exercise BOO (Brake on / off) circuit, and do a brief wide open throttle to bring the RPM up to 3000 to 4000. This tests the TPS and the VAF (vane air flow) meter.  You may also want to tap on the intake manifold with a small hammer or wrench to test the knock sensor. If you don’t tap on the intake, a code 25 for the KS will result.  Shortly after the dynamic response code, the KOER codes will be outputted.  These codes will each be outputted twice, just as in the KOEO test.

The wiggle test

If the scanner is left connected, roughly two minutes after the last code is outputted, the wiggle test mode will activate.  You can wiggle the harness, tap sensors, etc. in the same way as in the KOEO test.  Any fault codes will be stored in the continuous memory portion of the KOEO test.

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