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Test Procedure

WARNING: This page is about a different car, the 1989 Mercury Grand Marquis, 1989 Lincoln Town Car, 1989 Lincoln Mark VII, 1989 Ford Mustang, and 1989 Ford LTD Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: This test procedure has been revised based on updated procedures in Ford Technical Service Bulletin 89-18A-10.
  1. Deactivate Self-Test by disconnecting STI jumper wire. Start and run engine at 2000 RPM for 2 minutes to warm up HEGO sensor. Turn engine off and wait 10 seconds
  2. Activate "Self-Test". See KEY ON ENGINE OFF (KOEO) SELF-TEST  .
  3. Start engine. The engine ID code will be displayed. On vehicles equipped with Brake On/Off switch (BOO), the brake pedal MUST be depressed and released AFTER the ID code (within 1-2 seconds). On vehicles equipped with Power Steering Pressure Switch (PSPS), the steering wheel MUST be turned one-half turn and released AFTER the ID code. On vehicles equipped with an Overdrive Cancel Switch (OCS) the switch must be cycled AFTER the ID code.
    4. NOTE: DO NOT depress throttle during test unless a Dynamic Response code occurs.
  4. If a Dynamic Response code occurs, briefly depress accelerator pedal to Wide Open Throttle (WOT). A Dynamic Response code is a Code 1 or 10 displayed after the Engine ID code and before the Engine Running codes. DO NOT depress throttle during test unless a Dynamic Response code occurs. The KOER Self-Test service codes will then be displayed. Observe and record all codes.
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