Part 1 of 3

Chart A-3:

Ignition Circuit:

CIRCUIT DESCRIPTION:
Engine cranks but will not run, or engine may start, but immediately stops running. Battery condition and engine cranking speed are OK, and there is adequate fuel in the tank.

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

1. A MIL "CHECK ENGINE" light "ON" is a basic test to determine if there is battery and ignition voltage (12.0 volts) to the ECM. No DLC may be due to an ECM problem, and CHART A-2 will diagnose the ECM. If TP sensor is less than .2 volt, the TP 5 volt reference circuit could be shorted to ground. If TPS is over 2.5 volts, the ECM may be in the clear flood mode which will cause the engine not to start. The "Scan" tool should display engine speed during cranking if pulses, are received at the ECM.

2. Because the Electronic Ignition (EI) system uses two spark plugs and cables to complete the circuit of each coil, the opposite spark plug cable should be left connected.

3. This step determines if injectors or harness are cause of the problem. This test is performed with injectors 1 & 4 then 2 & 3 in parallel.

4. The test light should flash, indicating that the ECM is controlling the injectors. How bright the light flashes is not important.

5. Ignition may have to be cycled "ON" several times to obtain maximum fuel pressure.

6. Damage to the ECM injector driver may occur if any injector resistance measures less than 11.8 ohms (internal short to ignition CKT 439).

DIAGNOSTIC AIDS:

^ Water or foreign material can cause a no start condition during freezing weather. The engine may start after approximately 5 minutes in a heated shop. The problem may not recur until an overnight park in freezing temperatures.
^ An EGR valve sticking open may cause a low air/fuel ratio during cranking. Unless the ECM enters Clear Flood mode at the first indication of a flooding condition, a no start condition may be the result.
^ Low fuel pressure can result in a very lean air/fuel ratio. Related Tests, Information and Procedures
^ An A/C pressure sensor with an internal short to ground can cause a no start condition. Disconnect the A/C pressure sensor. If vehicle starts, replace faulty sensor.
^ A MAP sensor stuck between .5 and 2.5 volts can cause a no start condition. Disconnect the MAP sensor. If vehicle starts, replace faulty sensor.