Part 1 of 2

Chart A-3 (1 of 2):

Wiring Diagram For Engine No Start:

CIRCUIT DESCRIPTION:

This chart assumes that the battery condition, engine cranking speed, and fuel quantity are OK.


TEST DESCRIPTION: The 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 battery and ignition voltage (12.0 volts) to the ECM. No ALDL may be due to an ECM problem, and CHART A-2 will diagnose the ECM. If TPS is over 2.5 volts the engine may be in the clear flood mode which will cause starting problems. The engine will not start without crank sensor reference pulses. The "Scan" tool should display engine speed during cranking if pulses, are received at the ECM.
2. If the engine speed was indicated during cranking, the ignition module is receiving a crank signal. No spark at this test indicates the ignition module is not triggering the coil.
3. While cranking the engine, there should be no fuel spray with injector electrical connector disconnected. Replace an injector if it sprays fuel, or drips like a leaking water faucet.
4. Use an injector test light like J34730, BT8329 or equivalent, to test injector circuit. A blinking light indicates the ECM is controlling the injector.
5. This test will determine if there is fuel pressure at the injector and that the injector is operating. No fuel spray from the injector indicates a faulty fuel system or no ECM control of the injector.
6. This test will determine if the ignition module is not generating the reference pulse, or if the wiring or ECM is at fault. By touching and removing a test light to battery voltage on circuit 430, a reference pulse should be generated. If the engine speed is shown, the ECM and wiring are OK.

CAUTION: Not all SCAN testers are compatible with every system. A SCAN tool that produces faulty readings should NOT be used, and the problem should be reported to the tool manufacturer. Use of a faulty SCAN tool can result in improper diagnosis and unnecessary component replacement. Follow the proper instructions, located in the owners manual, for the specific SCAN tool being used.

DIAGNOSTIC AIDS:

1. Water or foreign material can cause a no start condition during freezing weather. The problem may occur during overnight parking in freezing temperatures. The engine may start after a few minutes in a heated shop.
2. An EGR valve sticking open may cause a lean air/fuel ratio during cranking. Unless the engine enters Clear Flood mode at the first indication of a flooding condition, a no start condition may be the result.
3. Low fuel pressure can result in a lean air/fuel ratio. See CHART A-7.