0395124 JOHNSON WATER TUBE

Table 1
Diagnostic Codes Table
SPN-FMI Code and Description Conditions which Generate this Code System Response
1268-5 Engine Ignition Coil #1 : Current Below Normal
1269-5 Engine Ignition Coil #2 : Current Below Normal
1270-5 Engine Ignition Coil #3 : Current Below Normal
1271-5 Engine Ignition Coil #4 : Current Below Normal
1272-5 Engine Ignition Coil #5 : Current Below Normal
1273-5 Engine Ignition Coil #6 : Current Below Normal
1274-5 Engine Ignition Coil #7 : Current Below Normal
1275-5 Engine Ignition Coil #8 : Current Below Normal
1276-5 Engine Ignition Coil #9 : Current Below Normal
1277-5 Engine Ignition Coil #10 : Current Below Normal
1278-5 Engine Ignition Coil #11 : Current Below Normal
1279-5 Engine Ignition Coil #12 : Current Below Normal While the engine is started, the Electronic Control Module (ECM) detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
The alarm output is activated.
Table 2
Diagnostic Codes Table
SPN-FMI Code and Description Conditions which Generate this Code System Response
1268-6 Engine Ignition Coil #1 : Current Above Normal
1269-6 Engine Ignition Coil #2 : Current Above Normal
1270-6 Engine Ignition Coil #3 : Current Above Normal
1271-6 Engine Ignition Coil #4 : Current Above Normal
1272-6 Engine Ignition Coil #5 : Current Above Normal
1273-6 Engine Ignition Coil #6 : Current Above Normal
1274-6 Engine Ignition Coil #7 : Current Above Normal
1275-6 Engine Ignition Coil #8 : Current Above Normal
1276-6 Engine Ignition Coil #9 : Current Above Normal
1277-6 Engine Ignition Coil #10 : Current Above Normal
1278-6 Engine Ignition Coil #11 : Current Above Normal
1279-6 Engine Ignition Coil #12 : Current Above Normal While the engine is started, the ECM detects an excessive current flow in the primary circuit for the ignition transformer. The code is logged.
The alarm output is activated. Note: The engine must be running in order for the above diagnostic codes to become active.The ECM has internal circuit drivers for the ignition transformers. Each circuit driver creates a signal of 108 V. The signal is sent to the primary circuits of the ignition transformers. The secondary circuits for the ignition transformers deliver high voltage (8,000 to 37,000 V) to the spark plugs. The external ignition wiring includes the following components:
Connectors at the rear of the ECM control box
Entry connectors at each valve cover base
Connectors for the primary connection at each transformerShort ignition harnesses are used inside the valve cover to make the connection from the connector at the valve cover base to the individual transformers.Some power circuits and returns are shared. Therefore, a single problem will generate either only one diagnostic code or multiple codes.Power for the Ignition Transformer PrimarySome power circuits send signals to a single cylinder. A high side short circuit will affect only that cylinder.Some power circuits send signals to more than one cylinder. For this reason, a high side short circuit will affect more than one cylinder.Return for the Ignition Transformer PrimaryThe ECM has internal returns for the ignition transformers. Some of the returns consist of groups of terminals that are connected via diodes inside the ECM. For this reason, a short in the return circuit to the +Battery will simultaneously affect all of the cylinders that are grouped.Refer to Tables 3 and 4 for the combinations of cylinders that can be affected by a condition.
Table 3
Wiring Faults and the Combinations of Cylinders that are Affected for 8 Cylinder Engines
Wiring Fault Affected Cylinders
Open on the driver side Only one cylinder is affected.
Return side open
Return side short to ground
Short to +Battery on the driver side
Return side short to +Battery 1, 4, 6, and 7
2, 3, 5, and 8
Table 4
Wiring Faults and the Combinations of Cylinders that are Affected for 12 Cylinder Engines
Wiring Fault Affected Cylinders
Open on the driver side Only one cylinder is affected.
Return side open
Return side short to ground
Cylinder 1 or 11
Short to +Battery on the driver side 1 and 11
Cylinder 2 or 12
Short to +Battery on the driver side 2 and 12
Cylinder 3 or 9
Short to +Battery on the driver side 3 and 9
Cylinder 4 or 10
Short to +Battery on the driver side 4 and 10
Cylinder 5 or 7
Short to +Battery on the driver side 5 and 7
Cylinder 6 or 8
Short to +Battery on the driver side 6 and 8
Return side short to +Battery 1, 5, and 9
2, 6, and 10
3, 7, and 11
4, 8, and 12 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, troubleshoot the circuits one at a time. This technique is an effective way to find the root cause.Logged diagnostic codes provide a historical record. Before you begin this procedure, use Caterpillar Electronic Technician (ET) to print a product summary report.The most likely causes of a 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.
Illustration 1 g02392638
Schematic for the primary ignition for 8 cylinder engines
Illustration 2 g02393460
Schematic for the primary ignition for 12 cylinder engines
Test Step 1. Inspect the Electrical Connectors and the Wiring
Remove the electrical power from the engine.