PISTON 1915603 - Caterpillar

System Operation Description:Use this procedure to troubleshoot suspect problems with the primary circuit for the ignition transformers.This procedure covers the following diagnostic codes:
301-5 Ignition Transformer Primary #1 : Current Below Normal
301-6 Ignition Transformer Primary #1 : Current Above Normal
302-5 Ignition Transformer Primary #2 : Current Below Normal
302-6 Ignition Transformer Primary #2 : Current Above Normal
303-5 Ignition Transformer Primary #3 : Current Below Normal
303-6 Ignition Transformer Primary #3 : Current Above Normal
304-5 Ignition Transformer Primary #4 : Current Below Normal
304-6 Ignition Transformer Primary #4 : Current Above Normal
305-5 Ignition Transformer Primary #5 : Current Below Normal
305-6 Ignition Transformer Primary #5 : Current Above Normal
306-5 Ignition Transformer Primary #6 : Current Below Normal
306-6 Ignition Transformer Primary #6 : Current Above Normal
307-5 Ignition Transformer Primary #7 : Current Below Normal
307-6 Ignition Transformer Primary #7 : Current Above Normal
308-5 Ignition Transformer Primary #8 : Current Below Normal
308-6 Ignition Transformer Primary #8 : Current Above Normal
309-5 Ignition Transformer Primary #9 : Current Below Normal
309-6 Ignition Transformer Primary #9 : Current Above Normal
310-5 Ignition Transformer Primary #10 : Current Below Normal
310-6 Ignition Transformer Primary #10 : Current Above Normal
311-5 Ignition Transformer Primary #11 : Current Below Normal
311-6 Ignition Transformer Primary #11 : Current Above Normal
312-5 Ignition Transformer Primary #12 : Current Below Normal
312-6 Ignition Transformer Primary #12 : Current Above Normal
313-5 Ignition Transformer Primary #13 : Current Below Normal
313-6 Ignition Transformer Primary #13 : Current Above Normal
314-5 Ignition Transformer Primary #14 : Current Below Normal
314-6 Ignition Transformer Primary #14 : Current Above Normal
315-5 Ignition Transformer Primary #15 : Current Below Normal
315-6 Ignition Transformer Primary #15 : Current Above Normal
316-5 Ignition Transformer Primary #16 : Current Below Normal
316-6 Ignition Transformer Primary #16 : Current Above NormalThe 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 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 circuit in the driver side Only one cylinder is affected.
Return side open
Return side short to ground
Cylinder 1