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HOMESERVICE MANUALSFORD1991PROBE GL, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - TESTS W/CODES - EECCODE-TO-TEST MENUCHECK ENGINE LIGHT
1991 Ford Probe GL, Standard

Check Engine Light

1991 Ford Probe GL, StandardSECTION Check Engine Light

1)  Connect a jumper wire between the STI connector and ground. See Figure and Figure . Turn ignition on. Observe CHECK ENGINE light. Record pulses to determine KOEO codes stored. Go to step 3).

NOTE: Reading code from ENGINE LIGHT pulses is similar to reading code from needle sweep of Analog Volt-Ohmmeter (VOM). See ANALOG VOLT-OHMMETER (VOM) under SELF-TEST.

2)  If no code is present and engine starts, begin KOER self-test; see step 6). If no code is present and engine does not start, go to the BASIC TESTING article.

3)  Erase code from ECA memory. See CLEARING CODES. Repeat step 1) to identify hard faults. If code(s) reappear, indicating it is a hard fault, repair fault as necessary. See CODE REFERENCE CHART  to determine the correct CIRCUIT TEST. Go to step 5).

4)  If code(s) does not reappear, fault is intermittent. Start KOER self-test. See step 6).

5)  Repeat step 3) until no code appears. Terminate KOEO self-test by turning ignition off and disconnecting jumper wire from STI connector. Start KOER self-test; see step 6).

6)  Start engine and run at 2000 RPM for 2 minutes to ensure EGO sensor is operating. Ensure vehicle is at normal operating temperature. Jumper STI connector to ground. Observe CHECK ENGINE light. Record pulses to determine KOER codes stored. Use CODE-TO-TEST MENU  to determine the appropriate CIRCUIT TEST.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.