Part 1 of 2

Chart A-3 Part 1 Of 2:

Wiring Diagram Chart A-3:

CIRCUIT DESCRIPTION:

This chart assumes that battery condition and engine cranking speed are OK, and there is adequate fuel in the tank.


TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. A "SERVICE ENGINE SOON light "ON" is a basic test to determine if there is a 12 volt supply and ignition 12 volts to the ECM. The injector test light should blink, indicating the ECM is in control of the injectors. How bright the light blinks is not important. However, the test light should be a J34730-2A or equivalent. The Scan tool can be used to verify that the ECM recognizes the reference signals. If it does, the Scan tool should read rpm during cranking.

2. Use fuel pressure gage J 34730-1 or equivalent. Wrap a shop towel around the fuel pressure tap to absorb any small amount of fuel leakage that may occur when installing the gage. This test will determine if the ignition module is not generating the reference pulse or if the wiring or ECM are at fault. By touching and removing a test light to 12 volts on CKT 430, a reference pulse should be generated. If rpm is indicated, the ECM and wiring are OK.

3. Because the direct ignition system uses two plugs and wires to complete the circuit of each coil, the opposite spark plug wire should be left connected. If rpm was indicated during crank, the ignition module is receiving a crank signal, but no spark at this test indicates the ignition module is not triggering the coils.

4. This test will determine if the ignition module is not triggering the problem coil or if the tested coil is at fault. This test could also be performed by using another known good coil.

5. If the test light is "OFF," the 20 amp fuse F.P./INJ could be blown or CKT 839 is open or shorted to ground.