Diagnostic Aids
Fuel-contaminated engine oil may affect some codes. If this is suspected, remove PCV valve from valve cover and repeat QUICK TEST. If problem is corrected, change engine oil and filter.
On CIRCUIT TEST H and CIRCUIT TEST J (Fuel Control), vacuum leaks in non-EEC related areas may also cause Code 41 or 91 to be displayed. Check the following: unmetered air leaks between airflow meter and throttle body, vacuum motors, engine seals, EGR system, PCV system, Canister Purge (CANP) and HEGO sensor. Code 42 or 92 may be caused by fuel-contaminated engine oil, ignition misfire, EGR system or CANP problems.
NOTE:
In the following tests, circuit diagrams and illustrations are courtesy of Ford Motor Co.
CIRCUIT TESTS are grouped as follows:
- A-C - No Start & Voltage Tests
- DA-DR - Input Sensor Tests
- FD-FF - Additional Input Component Tests
- G-J Fuel - Control Systems
- KC-X - ECA (Processor) Output Tests