Part 2 of 3
Chart A-3 (2 of 3):
Wiring Diagram For Engine No Start:
CIRCUIT DESCRIPTION:
A magnetic crank sensor is used to determine engine crankshaft position. The sensor is mounted in the engine block, near a slotted wheel on the crankshaft. The rotation of the wheel creates a flux change in the sensor, which produces a voltage signal. The DIS ignition module processes the signal and creates the reference pulses needed by the ECM to trigger the correct coil at the proper time. If the "Scan" tool does not show an engine cranking speed, and there is no spark at the plugs, the problem is in the DIS or the power and ground supplies to the module.
TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.
1. The DIS uses uses two plugs and wires to complete the circuit of each coil. The other spark plug wire in the circuit must be left connected to create a spark.
2. This test will determine if the 12.0 volt supply and a good ground is available at the DIS module.
3. This test will determine if the ignition module is not generating a reference pulse, or if the wiring or ECM are at fault. By applying and removing a test light to 12.0 volts on circuit 430, a reference pulse should be generated. If the engine speed is indicated, the ECM and wiring are OK.
4. This test determines 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 a known good coil to determine the problem. The secondary coil winding can be checked with a DVM. Readings of 5,000 to 10,000 ohms should be seen across the coil towers. There should be no continuity between the coil tower and ground.
5. This checks for continuity of the crank sensor and connections. This also checks the magnetism of the sensor.
6. An intermittent problem with the crank sensor may cause an intermittent "Cranks but won't run." As a precaution, the crank sensor should be replaced.
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.