How To Use Circuit Tests: Notes

NOTE: A breakout box, connected to vehicle harness at the ECA, is necessary to perform most circuit tests. References to Test Pin No. found in CIRCUIT TEST steps refer to test terminals on the manufacturer's breakout box. Circuit diagrams at the beginning of each test identify circuit and wire colors.

1) Ensure all non-EEC related faults found while performing steps in BASIC TESTING article have been corrected. DO NOT perform any CIRCUIT TEST unless specifically instructed by a QUICK TEST procedure. FOLLOW EACH TEST STEP IN ORDER UNTIL FAULT IS FOUND. DO NOT replace any part unless directed to do so. When more than one code is received, start with the first code displayed.

2) CIRCUIT TESTS check electrical circuits to make sure they are okay before replacing sensors or any other components. Always test circuits for continuity between sensor and ECA. Test all circuits for short to power, opens, or short to ground. Voltage Reference (VREF) and Voltage Power (VPWR) circuits should be tested with KOEO, or as specified in CIRCUIT TESTS.

3) DO NOT measure voltage or resistance at ECA, or connect any test light unless specified in testing procedure. All measurements are made by probing REAR of connector. Isolate both ends of a circuit and turn ignition off whenever checking for shorts or continuity, unless stated otherwise.

4) Disconnect solenoids and switches from harness before measuring continuity, resistance, or applying voltage. After each repair, check all component connections and repeat CIRCUIT TEST.

5) An open circuit is defined as a resistance reading of greater than 5 ohms. This specification tolerance may be too high for some items in the EEC-IV system. If resistance approaches 5 ohms, always clean the suspected connector and coat with protective dielectric silicone grease. A short is defined as a resistance reading of less than 10 k/ohms to ground, unless stated otherwise in the CIRCUIT TEST.

6) On CIRCUIT TEST H and CIRCUIT TEST J (Fuel Control), to prevent replacement of good components, be aware that the following non-EEC related areas may also be the cause of problem. These areas include ignition coil, distributor cap and rotor, spark plug wires, fouled spark plugs, canister purge problems, EGR valve and gasket, air filter, poor power and ground circuits, fuel pressure, intake and exhaust manifold leaks, engine not at normal operating temperature, and problems with PCV valves or fuel-contaminated engine oil.