Part 1 of 3

Chart A-3:

Ignition Circuit:

CIRCUIT DESCRIPTION:
Before using this chart, battery condition, engine cranking speed, and fuel quantity should be checked and verified as being OK.

TEST DESCRIPTION: Number(s) below refer to circled number(s) on the diagnostic chart.

1. An MIL (Check Engine) "ON" is a basic test to determine if there is battery and ignition voltage at the ECM.

^ No DLC data may be the result of an ECM problem, and CHART A-2 will diagnose an ECM problem.
^ If TP sensor is less than .2 volt, the TP sensor 5 volt reference circuit could be shorted to ground. If TP sensor is over 2.5 volts, the ECM could be in the "Clear Flood Mode" which may cause the engine to not start.
^ Compare coolant temperature with intake air temperature when engine is cold. If coolant temperature reading is 10 degrees greater or less than intake air temperature on a cold engine, check resistance of the Engine Coolant Temperature (ECT) sensor circuit or sensor. Compare resistance value to the "Diagnostic Aid" chart found on DTC 14 chart.
^ The scan tool should display rpm during cranking.

2. Because the Electronic Ignition (EI) uses two plugs and wires to complete the circuit of each coil, the opposite spark plug wire should be connected to a good ground.

3. This test is performed with injectors 1, 2, 3, & 4 in parallel.

4. This 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 ECM injector driver may occur if any injector resistance measures less than 11.6 ohms (internal injector short to ignition CKT 1149).

DIAGNOSTIC AIDS:

^ Water or contamination in fuel system may cause a no start condition during very cold or freezing weather. The engine may start after approximately 5 minutes in a heated shop.
^ An EGR valve sticking open can cause a rich air/fuel ratio during cranking. Unless the ECM enters "Clear Flood Mode" at the first indication of a flooding condition, it may result in a no start condition.
^ An A/C refrigerant pressure sensor with a internal short to ground can cause a no start condition. Disconnect the A/C refrigerant 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.