G3306B Petroleum Generator Set Engines Caterpillar

Use this procedure to troubleshoot a suspected problem with an ignition transformer. Also use this procedure if one of the diagnostic codes in Table 1 or Table 2 are active or easily repeated.

Table 1

Diagnostic Codes Table
Code and Description	Conditions which Generate this Code	System Response
1268-5 Engine Ignition Coil #1 : 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 amber warning lamp is illuminated. The red stop lamp is illuminated.
1268-6 Engine Ignition Coil #1 : Current Above Normal	While the engine is started, the ECM detects an excessive current flow in the primary circuit for the ignition transformer.
1269-5 Engine Ignition Coil #2 : 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 amber warning lamp is illuminated. The red stop lamp is illuminated.
1269-6 Engine Ignition Coil #2 : Current Above Normal	While the engine is started, the ECM detects an excessive current flow in the primary circuit for the ignition transformer.
1270-5 Engine Ignition Coil #3 : 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 amber warning lamp is illuminated. The red stop lamp is illuminated.
1270-6 Engine Ignition Coil #3 : Current Above Normal	While the engine is started, the ECM detects an excessive current flow in the primary circuit for the ignition transformer.
1271-5 Engine Ignition Coil #4 : 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 amber warning lamp is illuminated. The red stop lamp is illuminated.
1271-6 Engine Ignition Coil #4 : Current Above Normal	While the engine is started, the ECM detects an excessive current flow in the primary circuit for the ignition transformer.
1272-5 Engine Ignition Coil #5 : 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 amber warning lamp is illuminated. The red stop lamp is illuminated.
1272-6 Engine Ignition Coil #5 : Current Above Normal	While the engine is started, the ECM detects an excessive current flow in the primary circuit for the ignition transformer.
1273-5 Engine Ignition Coil #6 : 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 amber warning lamp is illuminated. The red stop lamp is illuminated.
1273-6 Engine Ignition Coil #6 : Current Above Normal	While the engine is started, the ECM detects an excessive current flow in the primary circuit for the ignition transformer.

Note: The engine must be running in order for the above diagnostic codes to become active.

Systems Operation

The ECM has internal power circuits that are used to energize the primary circuits for the ignition transformers. Each power circuit creates a signal of 108 v. The signal is sent from the ECM 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 is continuous from the ECM connector to each terminal that is for the ignition transformers.

Some power circuits and returns are shared. Therefore, a single problem will generate either only one diagnostic code or multiple codes.

Power and Return for the Ignition Transformer Primary

The power circuits that are internal to the ECM send signals to more than one cylinder. For this reason, a high side short circuit or a low side short circuit may affect more than one cylinder.

The return circuits that are internal to the ECM send signals to a single cylinder.

For the combinations of cylinders that can be affected by a condition, refer to Table 2.

Table 2

Diagnostic Conditions and the Combinations of Cylinders that are Affected
Diagnostic Condition	Cylinders
The power circuit for a single transformer shorted to the return circuit for that transformer.	Only one cylinder is affected.
Short to engine ground for the power circuit for cylinders 1, 2, or 5.	Transformers for cylinders 1, 2, and 5 will not be powered.
Short to engine ground for the power circuit for cylinders 3, 4, or 6.	Transformers for cylinders 3, 4, and 6 will not be powered.
Short to engine ground in a return circuit for cylinders 1, 2, or 5.	The other transformers for cylinders 1, 2, and 5 will receive half of the normal current for ignition.
Short to engine ground in a return circuit for cylinders 3, 4, or 6.	The other transformers for cylinders 3, 4, and 6 will receive half of the normal current from the ECM.
Short to the +Battery for the power circuit for cylinders 1, 2, or 5.	This problem may cause an engine misfire that is caused by a weak spark for the remainder of cylinders 1, 2, and 5.
Short to the +Battery for the power circuit for cylinders 3, 4, or 6.	This problem may cause an engine misfire that is caused by a weak spark for the remainder of cylinders 3, 4, and 6.
Short to the +Battery for the return circuit for cylinders 1, 2, or 5.	This problem may cause an engine misfire for the affected cylinder.
Short to the +Battery for the return circuit for cylinders 3, 4, or 6.

Because the circuits are organized in banks, multiple diagnostic codes can be activated for a single problem. If multiple diagnostic codes are active, troubleshooting the circuits one at a time is an effective way to find the root cause.

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 an ECM.

Illustration 1	g02029394
Schematic for the primary circuits of the ignition transformers

Illustration 2	g02029430
Location of the connectors at the ECM that are for the ignition transformers (right front engine view) (1) J2/P2 ECM connectors

Illustration 3	g02029463
Locations of the components for the ignition transformer primary (typical engine view) (2) Connections at the transformer for the ignition transformer primary

Table 3

Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and the Wiring A. Turn the main disconnect switch to the OFF position. B. Thoroughly inspect connectors (1) through (7) . Inspect all of the connectors that are associated with the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. C. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit. D. Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. E. Check the harness and wiring for abrasion and for pinch points from the sensors back to the ECM.	Connectors	Results: The harness and connectors appear to be OK. Proceed to Test Step 2 Results: There is a problem with the connectors and/or wiring. Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are coupled. Verify that the repair eliminates the problem.
2. Check for Diagnostic Codes that are Active or Logged A. Connect Cat® Electronic Technician (Cat® ET) to the service tool connector. B. Restore the electrical power to the ECM. C. Monitor the active diagnostic code screen on Cat ET. Check and record any diagnostic codes that are active or logged. Look for the following diagnostic codes: - 1268-5 - 1268-6 - 1269-5 - 1269-6 - 1270-5 - 1270-6 - 1271-5 - 1271-6 - 1272-5 - 1272-6 - 1273-5 - 1273-6 Note: Wait at least 30 seconds in order for the diagnostic codes to become active. D. Turn the main disconnect switch to the OFF position.	Codes	Results: No diagnostic codes are active or logged. Repair: There does not appear to be an electrical problem with the ignition system at this time. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect". Results: A short circuit diagnostic code -5 is active at this time. Proceed to Test Step 3. Results: An open circuit diagnostic code -5 is active at this time. Proceed to Test Step 4.
3. Create a Short Circuit at the Harness Connector for the Suspect Transformer A. Set the engine control to the OFF position. Remove the electrical power from the engine. B. Short the two terminal connectors together in order to create a test circuit through the ignition harness. C. Restore the electrical power to the engine. Start the engine. Note: The engine must be cranking or the engine must be running in order for the diagnostic codes to become active. D. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. E. Set the engine control to the OFF position. Remove electrical power from the engine. F. Restore the wiring to the original configuration.	Short Circuit	Results: A short circuit diagnostic code -6 is active when the jumper wire is installed. An open circuit diagnostic code -5 is active when the jumper wire is removed. Repair: The ECM detected the short circuit. There is an open circuit in the primary coils of the ignition transformer. Replace the ignition transformer. Verify that the repair eliminates the problem. Results: An open circuit -5 diagnostic code remained active after a short circuit was created at the terminal connectors of the suspect transformer. The ECM did not detect the short circuit. There may be a problem in the ignition harness that is between the ECM and the ignition transformer. Proceed to Test Step 5.
4. Create an Open Circuit at the Harness Connector for the Suspect Transformer A. Set the engine control to the OFF position. Remove the electrical power from the engine. B. Disconnect the terminal connectors from the suspect ignition transformer. C. Restore the electrical power to the engine. Start the engine. Note: The engine must be cranking or the engine must be running in order for the diagnostic codes to become active. D. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. E. Set the engine control to the OFF position. Remove electrical power from the engine.	Open Circuit	Results: An open circuit diagnostic code -5 is active with the transformer is disconnected. Repair: The -6 code changed to a -5 code. The ECM detected the open circuit that was created at the terminal connections of the ignition transformer. There is a short circuit in the primary coils of the ignition transformer. Replace the ignition transformer. Verify that the repair eliminates the problem. Results: A -5 code was not generated for the circuit with the disconnected transformer. The -6 code remained active for the affected cylinder. There may be a problem with the ignition harness. Proceed to Test Step 5.

Table 4

Troubleshooting Test Steps	Values	Results
5. Check for Proper Operation of the ECM A. Disconnect the J2/P2 ECM connector. B. Fabricate a jumper wire that is long enough to create an open between the ECM connector and engine ground. Crimp a connector socket to one end of the jumper wire. C. Remove the signal wire and the return wire for the suspect circuit from the ECM connector. Install a jumper wire into each of the terminal locations. D. Connect the J2/P2 ECM connector. E. Create an open at the ECM: a. Restore the electrical power to the engine ECM. Ensure that an open circuit condition exists, do not allow the loose end of the jumper wire to contact any wires or the engine ground. Note: The engine must be cranking or the engine must be running in order for the diagnostic codes to become active. b. Monitor the "Active Diagnostic Code" screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. F. Create a short at the ECM: a. Restore electrical power to the ECM. b. Monitor the "Active Diagnostic Code" screen on Cat ET. Check and record any active diagnostic codes. Note: The engine must be cranking or the engine must be running in order for the diagnostic codes to become active. G. Restore all wiring to the original configuration.	ECM	Results: An open circuit diagnostic code -5 is active when the circuit is open. A short circuit diagnostic code -6 is active when the jumper wire for the transformer is shorted to engine ground. Repair: The ECM is operating properly. The problem is in the harness wiring between the ECM and the connector for the ignition transformer. There may be a problem in one of the connectors. Repair the connectors or wiring and/or replace the connectors or wiring. Results: One of the following conditions exists: The open circuit diagnostic code -5 is not active when the circuit is open. The short circuit diagnostic code -6 is not active when the wire jumper is shorted to engine ground. Repair: The transformer and the harness are OK. The ECM does not appear to be operating properly. Perform the following procedure: 1. Temporarily connect a test ECM. Refer to Troubleshooting, "ECM - Replace". 2. Recheck the circuit in order to ensure that the original problem has been resolved. If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved. If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring.

If the procedure did not correct the issue, contact your Cat Dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).