HOUSING AS-TURBINE 1W7770 - Caterpillar

System Operation Description:The Electronic Control Module (ECM) has internal circuit drivers for the ignition transformers. Each circuit driver creates a signal of +108 volts. The signal goes to the high side of the primary circuits of the ignition transformers. The transformers deliver high voltage (8000 to 37,000 volts) to the spark plugs. The ignition wiring is continuous from the P2 connector to the individual transformers.The circuits for the drivers and the returns are shared inside the ECM. Therefore, a single problem may generate either only one diagnostic code or multiple codes.Circuit DriversEach circuit driver sends signals to two cylinders. For this reason, a high side short circuit will affect two cylinders.Return PathOutside the ECM, the return wire for each primary circuit consists of an individual wire. Internally, the return wires are grouped into four groups of four circuits. The circuits are connected via diodes. Because of the diodes, a return wire that has a short circuit to the −Battery side will affect only one cylinder. On the other hand, a return wire that has a short circuit to the +Battery side will simultaneously affect all four cylinders in the group.For the combinations of cylinders that can be affected by a condition, refer to Table 1.
Table 1
Wiring Faults and the Combinations of Cylinders that are Affected
Wiring Fault Cylinders
Open on the driver side Only one cylinder is affected.
Return side open
Return side short to ground
Cylinder 1 or 15
Short to +Battery on the driver side 1 and 15
Cylinder 2 or 16
Short to +Battery on the driver side 2 and 16
Cylinder 3 or 13
Short to +Battery on the driver side 3 and 13
Cylinder 4 or 14
Short to +Battery on the driver side 4 and 14
Cylinder 5 or 11
Short to +Battery on the driver side 5 and 11
Cylinder 6 or 12
Short to +Battery on the driver side 6 and 12
Cylinder 7 or 9
Short to +Battery on the driver side 7 and 9
Cylinder 8 or 10
Short to +Battery on the driver side 8 and 10
Return side short to +Battery 1, 3, 5, and 9
2, 4, 6, and 10
7, 11, 13, and 15
8, 12, 14, and 16 Because the circuits are in pairs or groups, multiple diagnostic codes can be activated for a single problem. If multiple diagnostic codes are active for the primary ignition, troubleshooting the circuits one at a time is an effective way to find the root cause.Logged diagnostic codes provide a historical record. Before you begin this procedure, use the Caterpillar Electronic Technician (ET) to print the logged codes to a file.The most likely causes of the diagnostic code are a poor electrical connection or a problem in a wiring harness. The next likely cause is a problem with an ignition transformer. The least likely cause is a problem with the ECM.
Illustration 1 g01106046
Schematic for the primary ignition
Test Step 1. Inspect the Electrical Connectors and Wiring
Illustration 2 g01074915
Terminal box
(1) J2/P2 connectors
(2) 16 amp circuit breaker
Set the engine control to the OFF/RESET mode. Switch 16 amp circuit breaker (2) to the OFF position. Note: For