G3516 TA Engine Caterpillar

Use this procedure to troubleshoot a problem with an ignition transformer. Also, use this procedure if one of the following diagnostic codes is active or easily repeated.

Table 1

J1939 Code and Description	Comments
1393-15 Engine Cylinder #1 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the Electronic Control Module (ECM) detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1394-15 Engine Cylinder #2 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1395-15 Engine Cylinder #3 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1396-15 Engine Cylinder #4 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1397-15 Engine Cylinder #5 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1398-15 Engine Cylinder #6 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1399-15 Engine Cylinder #7 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1400-15 Engine Cylinder #8 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1401-15 Engine Cylinder #9 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1402-15 Engine Cylinder #10 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1403-15 Engine Cylinder #11 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1404-15 Engine Cylinder #12 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1405-15 Engine Cylinder #13 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1406-15 Engine Cylinder #14 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1407-15 Engine Cylinder #15 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.
1408-15 Engine Cylinder #16 Ignition Transformer Secondary Output : High - least severe (1)	When the engine is running, the ECM detects a low current flow in the primary circuit for the ignition transformer. The code is logged.

The ignition transformers initiate combustion by providing high voltage to the spark plugs. The output from the secondary circuit of the transformer provides voltage to the terminals of the spark plug. The transformers are located underneath the valve covers. Each transformer is grounded to a valve cover via a ground spring.

The secondary circuit of the transformer provides an initial 8,000 to 37,000 V to the spark plug. This voltage ionizes the air that is in the spark plug gap and this action generates a spark in the air gap. This voltage is then reduced to about 1,000 V. The total duration of the spark is approximately 400 microseconds.

Each Electronic Control Module (ECM) can diagnose the primary circuit of the ignition transformers for open circuits and/or for short circuits. Secondary open circuits and short circuits will not directly shutdown the engine. However, these conditions may lead to misfire which can cause lugging of the engine. Lugging of the engine can cause a shutdown.

Note: Ignition transformers that are used with Electronic Ignition Systems (EIS) are not interchangeable with the transformers that are used with ADEM III and up systems. Be sure not to interchange these components on any engine.

Caterpillar spark plugs are high-voltage devices with internal resistors. The spark plugs operate at a voltage that is greater than 5,000 V.

Most ignition systems are affected by resistance in the secondary circuit. If a measurement of the resistance is desired, a megohmmeter must be used. A low voltage multimeter will not provide a reliable reading of the resistance because oxidation of the spark plug internal components will affect the readings for those meters.

If a diagnostic code is generated for the ignition transformer's secondary circuit, the spark plug may need to be replaced. Misfire and a cold cylinder are other indications of a worn spark plug. Use Cat ET to monitor the exhaust port temperatures in order to locate a cold cylinder.

The service life of the spark plugs is affected by fouling due to deposits from the oil and by peak voltage. Maintenance of the ignition system is also affected by voltage. Higher voltage is required by higher inlet manifold air pressure, a higher compression ratio, or retardation of the timing. Higher voltage reduces the service life of components such as spark plugs, wires, and transformers.

To help predict the spark plug's service life, use Cat ET to monitor the secondary voltage. The value is expressed as a percent of secondary voltage. The value increases as the spark plug gap wears over time. A new spark plug is at 0 percent. A value over 90 percent may require maintenance. A spark plug at 100 percent requires replacement. Maintaining a log of this voltage at a particular site will help to determine the proper interval for replacement of the spark plugs.

For instructions on inspection and replacement of the spark plug, refer to the engine's Operation and Maintenance Manual. For more information on the spark plug, refer to the engine's Specifications manual.

Table 2

Parameters for the Status Screens on Cat ET
Screen 1	Screen 2
"Cylinder #1 Transformer Secondary Output Voltage Percentage"	"Cylinder #2 Transformer Secondary Output Voltage Percentage"
"Cylinder #3 Transformer Secondary Output Voltage Percentage"	"Cylinder #4 Transformer Secondary Output Voltage Percentage"
"Cylinder #5 Transformer Secondary Output Voltage Percentage"	"Cylinder #6 Transformer Secondary Output Voltage Percentage"
"Cylinder #7 Transformer Secondary Output Voltage Percentage"	"Cylinder #8 Transformer Secondary Output Voltage Percentage"
"Cylinder #9 Transformer Secondary Output Voltage Percentage"	"Cylinder #10 Transformer Secondary Output Voltage Percentage"
"Cylinder #11 Transformer Secondary Output Voltage Percentage"	"Cylinder #12 Transformer Secondary Output Voltage Percentage"
"Cylinder #13 Transformer Secondary Output Voltage Percentage"	"Cylinder #14 Transformer Secondary Output Voltage Percentage"
"Cylinder #15 Transformer Secondary Output Voltage Percentage"	"Cylinder #16 Transformer Secondary Output Voltage Percentage"
"Cylinder #17 Transformer Secondary Output Voltage Percentage"	"Cylinder #18 Transformer Secondary Output Voltage Percentage"
"Cylinder #19 Transformer Secondary Output Voltage Percentage"	"Cylinder #20 Transformer Secondary Output Voltage Percentage"

Table 3

Troubleshooting Test Steps	Values	Results
1. Use Caterpillar Electronic Technician (ET) to Check the Output of the Transformers NOTE: The engine must be running in order for these diagnostic codes to become active. A. Connect Caterpillar Electronic Technician (ET) to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools", if necessary. B. Set up two status screens for Cat ET. Refer to table 2. C. Start the engine. Allow the engine to warm to normal operating temperature. Apply the normal load at rated speed. D. Monitor the two status screens. Record the value of the output for the secondary circuit of each transformer.	Secondary Output Voltage Percentage	Results: The displayed values are OK. The displayed value of the output for the secondary circuit of each transformer is between 1 and 90 percent. Repair: The ignition system components are operating properly. Investigate other possible root causes of the problem. Troubleshoot the symptom. Refer to Troubleshooting, "Symptom Troubleshooting". Results: At least one of the displayed values are NOT OK. At least one of the outputs displayed a value of 0 percent or a value that is greater than 90 percent. The ignition system components require maintenance. Proceed to Test Step 2.
2. Inspect the Condition of the Transformer Set the engine control switch to the OFF/RESET position. Remove the electrical power from the engine. Remove the valve cover from the suspect cylinder. Disconnect the harness connector (2) from the transformer. Remove transformer (1) from the engine. Refer to Illustration 1. Inspect the body of transformer (3). Check that the screws (4) for ground spring (5) are tight and secure. Verify that there is no visible corrosion or damage to the transformer. Check that the connector (7) that is for the spark plug is free of corrosion and/or for damage. Inspect O-ring seal (9) inside extension (8) for damage. Check for a secure connection between the transformer and the spark plug. Check extension (8) near spacer (6) for signs of pin holes that can be caused by arcing. Clean any deposits inside the extension. Use a 6V-7093 Brush with isopropyl alcohol.	Transformer Condition	Results: The transformer is OK. Proceed to Test Step 3. Results: The transformer is NOT OK. The inspection found a problem with the transformer. Repair: Perform the following procedure: 1. Repair the transformer, when possible. Replace the transformer, if necessary. Ensure that the specified transformer for the specific engine application is used. 2. Before returning the engine to service, clear the logged diagnostic codes.

Illustration 1	g03359760
Location of the components of the ignition transformer (1) Transformer (2) Transformer connector (3) Transformer (4) Screws for the ground spring (5) Ground spring (6) Spacer (7) Connector for the spark plug (8) Extension (9) O-ring seal

Table 4

Troubleshooting Test Steps	Values	Results
3. Test the Primary Circuit of the Transformer A. Check the primary circuit by measuring the voltage drop across the blocking diode. B. Set the multi-meter to the diode scale. Connect the multi-meter leads across the terminals of the transformer connector (11). The polarity of the leads is not important for the first measurement. Record the voltage that is indicated by the meter. Refer to Illustration 2. C. Reverse the polarity of the multi-meter leads. Record the voltage that is indicated by the meter.	Primary Circuit Condition	Results: The transformer is OK. One measurement indicates an open circuit. The other measurement indicates approximately 0.450 V. Proceed to Test Step 4. Results: The transformer is NOT OK. At least one of the measurements is incorrect. Repair: Perform the following procedure: 1. Replace the ignition transformer. Ensure that the specified transformer for the specific engine application is used. 2. Before returning the engine to service, clear the logged diagnostic codes.

Illustration 2	g03359750
Test points at the ignition transformer (partial cutaway view) (11) Test points at the input terminals for the primary circuit (12) Test points for the secondary circuit

Table 5

Troubleshooting Test Steps	Values	Results
4. Test the Secondary Circuit of the Transformer A. Measure the resistance of the secondary circuit. NOTE: The resistance of the secondary coil will vary with the temperature. Refer to Illustration 3. A measured resistance that is within 1,000 Ohms is acceptable. B. Set the multi-meter to the 40,000 Ohm scale. Connect the leads of the multi-meter between test points (12). Measure the resistance between the screw for the ground spring and the connector for the spark plug. Refer to Illustration 2.	Secondary Circuit Condition	Results: The transformer is OK. The measurement is within the acceptable tolerance. Proceed to Test Step 5. Results: The transformer is NOT OK. The measurement is not within the acceptable tolerance. Repair: Perform the following procedure: 1. Replace the ignition transformer. Ensure that the specified transformer for the specific engine application is used. 2. Before returning the engine to service, clear the logged diagnostic codes.

Illustration 3	g03359749
Resistance versus temperature for the 418-4862 Ignition Transformer Gp

Table 6

Troubleshooting Test Steps	Values	Results
5. Test the Spark Plug A. Remove the electrical power from the engine. B. Perform the following procedures according to the instructions in the engine's Operation and Maintenance Manual. a. Remove the spark plug from the cylinder head. b. Inspect the spark plug. c. Clean the spark plug. C. Measure the spark plug's resistance after the spark plug has been cleaned. NOTE: A standard Ohmmeter cannot be used for measuring the resistance of a used spark plug. a. Use the 142-5055 Insulation Testing Gp (ELECTRICAL) to measure the resistance of the spark plug. Follow the warnings and instructions that are provided with the tool. b. Connect the red lead of the tester to the terminal post. The spark plug's ground tab may obstruct the placement of the testing group's contact lead. You may need to connect a smaller lead to the center electrode. Then connect the black lead of the tester to the smaller lead. c. Use the tester's "20 KΩ" scale.	Spark Plug Condition	Results: The spark plug is OK. The resistance is less than 10,000 Ohms. Proceed to Test Step 6. Results: The spark plug is NOT OK. The spark plug is not in good condition and/or the resistance is not within the specification. Repair: Perform the following procedure: 1. Discard the spark plug. Install a new spark plug according to Operation and Maintenance Manual, "Ignition System Spark Plugs - Inspect/Adjust/Replace - Spark Plugs with Adjustable Electrode Gaps". 2. Reset the control system. Restart the engine. Verify the repair by checking the output of the transformers. 3. Before returning the engine to service, clear the logged diagnostic codes.
6. Start the Engine and Check the Output of the Transformers A. Install the spark plug according to the instructions in the engine's Operation and Maintenance Manual. B. Install the transformer and the valve cover. C. Reset the control system. Clear any logged diagnostic codes. D. Start the engine. Apply the normal load at rated speed. Allow the engine to warm to normal operating temperature. E. Use Cat ET to check the value of the output for the secondary circuit of each transformer.	Secondary Output Voltage Percentage	Results: The output from each transformer is OK. Return the engine to service. Before returning the engine to service, clear the logged diagnostic codes. Results: The output of at least one transformer is NOT OK. Proceed to Test Step 7.
7. Isolate the Spark Plug and the Transformer A. Switch the suspect transformer with a transformer that is known to be good, from a different cylinder. Install the transformers. Install the valve covers. B. Reset the control system. Clear any logged diagnostic codes. C. Start the engine. Apply the normal load at rated speed. Allow the engine to warm to normal operating temperature. D. Use Cat ET to check the value of the output for the secondary circuit of each transformer.	Determine Failed Components	Results: The output from the suspect transformer is OK. The ignition problem remained with the original cylinder. Repair: If the problem is not accompanied by a diagnostic code, there may be a mechanical problem that is affecting cylinder performance. If a mechanical problem is suspected, refer to Troubleshooting, "Symptom Troubleshooting" for the appropriate test procedure. If the problem is accompanied by a diagnostic code, there is an electrical problem with the engine. Refer to Troubleshooting, "Diagnostic Trouble Code List" for the appropriate test procedure. Results: The output from the suspect transformer is NOT OK. The ignition problem followed the suspect transformer. Repair: Perform the following procedure: 1. Replace the transformer. Ensure that the specified transformer for the specific engine application is used. 2. Before returning the engine to service, clear the logged diagnostic codes.