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Home >> Ford >> 1990 >> F-Super Duty 7.3 M, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Test H - Fuel Control >> Test H: Step 11
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Test H: Step 11

11) Code 41 or 91: Fuel Control Always Lean  If vehicle is equipped with dual HEGOs, Code 41 refers to the Right (rear) HEGO and Code 91 refers to the Left (front) HEGO. Run engine at 2000 RPM for 2 minutes. Turn key off and wait 10 seconds. Rerun KOER Self-Test. Check for Code 41 or 91. If Code 41 or 91 is not displayed, go to step 20). If Code 41 or 91 is displayed, go to appropriate step number as listed below.