Do the tests it states and don't assume something is
good, verify it as the chart states. It should lead you to the root cause of your concern, or another chart. let me
know if you need the next chart.
Test Description Numbers below refer to circled numbers on diagnostic chart.
1. Perform On-Board Diagnostic (OBD) system check to determine if the ECM and MIL light are functioning
2. Chart C-4 will address all problems related to the causes of a no spark condition.
3. The test light should blink, indicating the ECM injector drivers are operating and providing a ground path for
the injectors. If the test light blinks more dimly on one or a few injectors than on the rest, shorted injector(s)
are indicated. Check resistance through each injector and compare values.
4. Use fuel
pressure gauge J-34730-1 or
equivalent. Relieve fuel
system pressure before
fuel system connections and use a
shop towel to absorb any fuel that may leak from lines when installing gauge.
5. All injectors should be within 1.O Ohm of each other and should not be less than 10 Ohms at 21°C
- An EGR
valve sticking open can cause a
low air/fuel ratio during cranking.
engine enters "Clear Flood" at the
first indication of a
flooding condition, it can result
in a no start.
- A defective MAP
sensor may cause a no start or
a stall after start. Disconnect the sensor. The ECM will use a default value for the sensor. If the condition is
corrected and the connections are OK, replace the sensor.
Test Description: Number(s) below refer to circled number(s) on the
1. Checks for 12 volt supply to injectors. Due to the injectors wired in parallel there a light should be "ON" at
2. Checks continuity of CKT 467 and CKT 468.
3. All checks made to this point would indicate that the ECM is at fault. However, there is a possibility of CKT
467 or CKT 468 being shorted to a voltage source either in the engine harness or in the injector harness.
To test for this condition:
- Disconnect all injectors.
- Ignition "ON."
- Probe CKT 467 and CKT 468 on the ECM side of injector harness with a test light connected to ground. (Test one
injector harness on each side of engine.) There should be no light. If light is "ON"
repair short to voltage.
- If OK, check the resistance of the injectors.
- Should be 10 Ohms or more.
- Check injector harness connector. Be sure terminals are not backed out of connector and contacting each
- If all OK, replace ECM.