G3500 A3 Engines Caterpillar

Use this procedure to troubleshoot the following diagnostic codes:

• 301-5 through 316-5 Ignition Transformer Primary #1 current below normal through Ignition Transformer Primary #16 current below normal

• 301-6 through 316-6 Ignition Transformer Primary #1 current above normal through Ignition Transformer Primary #16 current above normal

The Electronic Control Module (ECM) has internal circuit drivers for the ignition transformers. Each circuit driver creates a signal of approximately +108 volts. The signal goes to the high side of the primary circuits of the ignition transformers. The transformers deliver high voltage (8,000 to 37,000 volts) to the spark plugs. The ignition wiring is routed from the P2 ECM connector to a bulkhead connector. Internal wiring runs from the bulkhead connector to the individual transformers.

The circuits for the drivers and the returns are shared inside the ECM. Therefore, a single problem may generate one diagnostic code or multiple codes.

Circuit Drivers

Each circuit driver sends signals to two cylinders. For this reason, a high side short circuit will affect two cylinders.

Return Circuit

In the wiring that is external to 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 cylinders in the group.

For the combinations of cylinders that can be affected by a condition, refer to Table 1.

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.

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	g01251202
Schematic for the primary ignition on 16 cylinder engines

Illustration 2	g01251203
Schematic for the primary ignition on 12 cylinder engines

Illustration 3	g01251204
Schematic for the primary ignition on 8 cylinder engines

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Set the engine control to the OFF/RESET position.

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Illustration 4	g01392488
Location of the connectors for the primary circuit of the ignition transformers (typical left front engine view) (1) J2/P2 ECM connectors (2) Bulkhead connector

Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".

2. Thoroughly inspect connectors (1) and (2) .

   1. Check the allen head screw for each of the ECM connectors for the proper torque.

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit of the ignition system.

3. Inspect the bulkhead connector.

4. Check the ignition harness and wiring for abrasion and for pinch points from the bulkhead connector to the ECM connector.

Expected Result:

All of the connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.

Results:

• OK - The components are in good condition with proper connections. Proceed to Test Step 2.

• Not OK - The components are not in good condition and/or at least one connection is improper.

  Repair: Perform the necessary repairs and/or replace parts, if necessary.

  STOP

Test Step 2. Check for Diagnostic Codes for the Primary Circuit

1. Establish communication between Caterpillar Electronic Technician (ET) and the ECM. Refer to Troubleshooting, "Electronic Service Tools", if necessary.

2. Attempt to start the engine. Use Cat ET to determine if the following codes are active or logged:
   • 301-5 Ignition Transformer Primary #1 current below normal through 316-5 Ignition Transformer Primary #16 current below normal

   • 301-6 Ignition Transformer Primary #1 current above normal through 316-6 Ignition Transformer Primary #16 current above normal

   Note: If a diagnostic code for the primary circuit is logged but not currently active, attempt to repeat the condition that generated the code. Run the engine to full operating temperature.

Expected Result:

None of the above diagnostic codes are active.

Results:

• OK - There are only logged codes that are related to the primary circuit of the ignition transformers.

  Repair: There may be an intermittent problem in the ignition harness. Perform the following steps:

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  Ignition systems can cause electrical shocks. Avoid contacting the ignition system components and wiring. Do not attempt to remove the valve covers when the engine is operating. The transformers are grounded to the valve covers. Personal injury or death may result and the ignition system will be damaged if the valve covers are removed during engine operation. The engine will not operate without the valve covers.

  1. Set the engine control to the OFF/RESET position.
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  Illustration 5	g01392533
  Section view of valve cover and transformer (3) Valve cover (4) Transformer (5) 2-pin connector (6) Camshaft cover (7) Ignition harness

  2. Remove valve cover (3) for the suspect cylinder. Inspect the harness and the 2-pin connector (5) of transformer (4) .

  3. Remove camshaft cover (6) and inspect ignition harness (7) for abrasion, exposed wires, and damage.

  4. Inspect the engine harness. Refer to Troubleshooting, "Inspecting Electrical Connectors".

  STOP

• Active -5 code - There is a -5 code that is active at this time. There is an open in the primary circuit. Proceed to Test Step 5.

• Active -6 code - There is a -6 code that is active at this time. There is a short in the primary circuit. Proceed to Test Step 3.

Test Step 3. Check the Transformer's Primary Circuit and the Secondary Circuit

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Ignition systems can cause electrical shocks. Avoid contacting the ignition system components and wiring. Do not attempt to remove the valve covers when the engine is operating. The transformers are grounded to the valve covers. Personal injury or death may result and the ignition system will be damaged if the valve covers are removed during engine operation. The engine will not operate without the valve covers.

1. Set the engine control to the OFF/RESET position.

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Illustration 6	g01392540
Section view of valve cover and transformer (3) Valve cover (4) Transformer (5) 2-pin connector

2. Remove valve cover (3) for the suspect cylinder.

3. Disconnect 2-pin connector (4) . Visually inspect the 2-pin connector for corrosion and/or damage.

4. Remove transformer (5) from the cylinder head.

5. Check the primary circuit and check the secondary circuit according to Systems Operation/Testing and Adjusting, "Ignition Transformer".

Expected Result:

The ignition transformer is within the specifications that are outlined in Systems Operation/Testing and Adjusting, "Ignition Transformer".

Results:

• OK - All of the measurements are correct.

  Repair: Perform the following steps:

  1. Install the spark plug according to the instructions in Operation and Maintenance Manual, "Ignition System Spark Plugs - Check/Adjust/Replace".

  2. Switch the suspect transformer with a transformer from a different cylinder that is known to be good. Install the transformers. Install the valve covers.

  3. Reset the control system. Restart the engine. Clear any logged codes.

  4. Operate the engine. Check for a recurrence of the problem.
  If the problem stays with the suspect transformer, replace the transformer.

  If the problem stays with the suspect cylinder, proceed to Test Step 4.

• Not OK - At least one of the three measurements is incorrect.

  Repair: Replace the ignition transformer. Make sure that you use the correct transformer for the G3500 (A3) Engine.

  STOP

Test Step 4. Check for a Short Circuit Between the P2 ECM Connector and the Bulkhead Connector

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There is a strong electrical shock hazard when the crankshaft is rotating. Do not touch the wires that are associated with the ignition system when the engine is cranking or when the engine is running.

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NOTICE
The air inlet, the cylinders, and the exhaust system can be filled with fuel when the gas supply is ON, the ignition system is disabled, and the engine is cranked. The unburned fuel can ignite unexpectedly and cause damage. Turn OFF the gas supply before you perform this step.

1. Shut off the fuel supply. Set the engine control to the OFF position. Disconnect the ignition harness from the bulkhead connector.

2. Set the engine control to the START position and observe the "Active Diagnostic" screen of Cat ET while you crank the engine.

   Note: Additional diagnostic codes will be generated during this test. Disregard the additional codes. Look for the original -6 code.

Expected Result:

The original -6 code is active when the bulkhead connector is disconnected.

Results:

• OK - The original -6 code was generated after the bulkhead connector was disconnected.

  Repair: The short circuit is probably located in the harness between the bulkhead connector and the P2 ECM connector. Locate the short circuit. Refer to Troubleshooting, "Inspecting Electrical Connectors". Perform the necessary repairs.

  If the condition is not corrected, proceed to Test Step 5.

• Not OK - The original -6 code was not generated after the bulkhead connector was disconnected. The short circuit is in the ignition harness that is inside of the engine block. Proceed to Test Step 8.

Test Step 5. Create an Open Circuit in the Ignition Harness

Show/hide table

Ignition systems can cause electrical shocks. Avoid contacting the ignition system components and wiring. Do not attempt to remove the valve covers when the engine is operating. The transformers are grounded to the valve covers. Personal injury or death may result and the ignition system will be damaged if the valve covers are removed during engine operation. The engine will not operate without the valve covers.

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NOTICE
The air inlet, the cylinders, and the exhaust system can be filled with fuel when the gas supply is ON, the ignition system is disabled, and the engine is cranked. The unburned fuel can ignite unexpectedly and cause damage. Turn OFF the gas supply before you perform this step.

1. Shut off the fuel supply. Set the engine control to the OFF/RESET position.

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Illustration 7	g01396497
Section view of a valve cover and ignition transformer (3) Valve cover (5) 2-pin connector for the ignition harness

2. Remove valve cover (3) for the suspect cylinder.

3. Disconnect the 2-pin connector (5) . Inspect the connectors of the harness and the transformer for damage and/or corrosion. Inspect the harness.

4. Fabricate a jumper wire that is long enough to create a test circuit across the 2-pin connector. Crimp connector sockets to each end of the jumper wire.

5. Install the jumper wire across terminals 1 and 2 on the harness side of the connector for the transformer.

6. Set the engine control to the START position and observe the "Active Diagnostic" screen of Cat ET while you crank the engine. Look for the original -5 code.

Expected Result:

The original -5 code is active.

Results:

• OK - The original -5 code was generated after a short circuit was created in the ignition harness. The ECM did not detect the jumper wire. Proceed to Test Step 6.

• Not OK - Cat ET displayed an active -6 code after a short circuit was created in the ignition harness.

  Repair: The harness and the ECM are OK. Perform the following steps:

  Show/hide table

  There is a strong electrical shock hazard when the crankshaft is rotating. Do not touch the wires that are associated with the ignition system when the engine is cranking or when the engine is running.

  Show/hide table

  NOTICE
  The air inlet, the cylinders, and the exhaust system can be filled with fuel when the gas supply is ON, the ignition system is disabled, and the engine is cranked. The unburned fuel can ignite unexpectedly and cause damage. Turn OFF the gas supply before you perform this step.

  1. Set the engine control to the OFF/RESET position.

  2. Remove the jumper wire from the 2-pin connector of the ignition harness. Thoroughly inspect the connectors for the transformer. Refer to Troubleshooting, "Inspecting Electrical Connectors".

  3. Connect the ignition harness to the transformer.

  4. Set the engine control to the START position and observe the "Active Diagnostic" screen of Cat ET while you crank the engine. Look for the original -5 code.

  5. If the original -5 code is generated, set the engine control to the OFF/RESET position.

  6. Replace the transformer. Make sure that you use the correct transformer for the G3500 (A3) Engine.

  7. Clear all of the logged diagnostic codes.

  STOP

Test Step 6. Check the Engine Harness for an Open Circuit

Show/hide table

There is a strong electrical shock hazard when the crankshaft is rotating. Do not touch the wires that are associated with the ignition system when the engine is cranking or when the engine is running.

Show/hide table

NOTICE
The air inlet, the cylinders, and the exhaust system can be filled with fuel when the gas supply is ON, the ignition system is disabled, and the engine is cranked. The unburned fuel can ignite unexpectedly and cause damage. Turn OFF the gas supply before you perform this step.

1. Shut off the fuel supply. Set the engine control to the OFF/RESET position.

2. Disconnect the bulkhead connector.

3. Fabricate a jumper wire that is long enough to create a test circuit across the bulkhead connector. Crimp connector sockets to each end of the jumper wire.

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Illustration 8	g00720061
Terminal locations for the harness connector of the ignition harness

4. Install the jumper wire into the terminals of the connector on the external engine harness side of the bulkhead connector for the suspect cylinder.

   The cylinders and the terminals are identified in Illustrations 1, 2, and 3.

5. Set the engine control to the START position and observe the "Active Diagnostic" screen of Cat ET while you crank the engine. Look for the original -5 diagnostic code.

Expected Result:

The original -5 code is not active. However, a -6 code is generated for the suspect cylinder.

Results:

• OK - When the jumper wire was installed into the harness, the original -5 code was not active. However, a -6 code was generated for the suspect cylinder.

  Repair: The external engine harness and the ECM are OK. The internal ignition harness in the engine block has an open circuit. Perform the following steps:

  1. Set the engine control to the OFF/RESET position.

  2. Remove the camshaft covers from the bank of the engine with the suspect cylinder.

  3. Inspect the internal ignition harness for abrasion, exposed wires, or other damage. Be sure to inspect the harness inside the front of the engine. Repair the harness, when possible. Replace the harness, if necessary.

  STOP

• Not OK - When the jumper wire was installed into the external engine harness, the original -5 code was generated.

  Repair: The ECM did not detect the jumper wire. The open circuit is probably in the external engine harness. Refer to Troubleshooting, "Inspecting Electrical Connectors". Perform the necessary repairs.

  If the condition is not corrected, proceed to Test Step 7.

Test Step 7. Check for the Proper Operation of the ECM

Show/hide table

There is a strong electrical shock hazard when the crankshaft is rotating. Do not touch the wires that are associated with the ignition system when the engine is cranking or when the engine is running.

Show/hide table

NOTICE
The air inlet, the cylinders, and the exhaust system can be filled with fuel when the gas supply is ON, the ignition system is disabled, and the engine is cranked. The unburned fuel can ignite unexpectedly and cause damage. Turn OFF the gas supply before you perform this step.

1. Set the engine control to the OFF/RESET position.

2. Disconnect the P2 ECM connector. Thoroughly inspect the J2 and P2 ECM connectors for corrosion, moisture, and other damage. Make repairs, if necessary.

3. Remove the wires for the suspect circuit from the P2 ECM connector. The location of the wiring for the suspect circuit depends on the original diagnostic code.

   Note: For identification of the terminal locations, refer to Illustrations 1, 2, and 3.

   1. If you are troubleshooting a -6 code, remove the wire from the terminal location that is for the circuit driver of the suspect cylinder.

   2. If you are troubleshooting a -5 code, remove the wires from the terminal locations that are for the circuit driver and from the return of the suspect cylinder. Fabricate a jumper wire that is long enough to create a test circuit across the P2 ECM connector. Crimp connector sockets to each end of the jumper wire. Install the ends of the jumper wire into the terminals for the removed wires.

4. Connect the P2 ECM connector. If any valve covers were removed, install the valve covers.

5. Set the engine control to the START position and observe the "Active Diagnostic" screen of Cat ET while you crank the engine.

Expected Result:

A -5 code is generated for the circuit after removal of the wire for the circuit driver.

A -6 code is generated for the circuit with the installed jumper wire.

Results:

• OK - A diagnostic code was generated according to the test results.

  Repair: The ECM is operating correctly. There is a problem with the ignition harness. Set the engine control to the OFF/RESET position. Repair the harness, when possible. Replace the harness, if necessary.

  STOP

• Not OK - A diagnostic code was not generated according to the results that are given above. There is a problem with the ECM.

  Repair: There may be a problem with the ECM. Temporarily install a new ECM. Refer to Troubleshooting, "Replacing the ECM".If the problem is resolved with the new ECM, install the original ECM and verify that the problem returns. If the new ECM operates correctly and the original ECM does not operate correctly, replace the ECM. Refer to Troubleshooting, "Replacing the ECM".

  STOP

Test Step 8. Check the Ignition Transformer for a Short Circuit

Show/hide table

Ignition systems can cause electrical shocks. Avoid contacting the ignition system components and wiring. Do not attempt to remove the valve covers when the engine is operating. The transformers are grounded to the valve covers. Personal injury or death may result and the ignition system will be damaged if the valve covers are removed during engine operation. The engine will not operate without the valve covers.

Show/hide table

NOTICE
The air inlet, the cylinders, and the exhaust system can be filled with fuel when the gas supply is ON, the ignition system is disabled, and the engine is cranked. The unburned fuel can ignite unexpectedly and cause damage. Turn OFF the gas supply before you perform this step.

1. Set the engine control to the OFF/RESET position.

2. Remove the valve cover for the suspect cylinder.

3. Inspect the ignition harness for abrasion, exposed wires, or other damage.

4. Disconnect the ignition harness from the transformer. Thoroughly inspect the 2-pin connector on the transformer.

5. Set the engine control to the COOLDOWN/STOP position.

6. Do not connect the transformer. Set the engine control to the START position and observe the "Active Diagnostic" screen of Cat ET while you crank the engine.

Expected Result:

A -5 diagnostic code is generated for the circuit with the disconnected transformer.

Results:

• OK - A -5 diagnostic code was generated for the circuit with the disconnected transformer.

  Repair: Perform the following steps:

  Show/hide table

  There is a strong electrical shock hazard when the crankshaft is rotating. Do not touch the wires that are associated with the ignition system when the engine is cranking or when the engine is running.

  Show/hide table

  NOTICE
  The air inlet, the cylinders, and the exhaust system can be filled with fuel when the gas supply is ON, the ignition system is disabled, and the engine is cranked. The unburned fuel can ignite unexpectedly and cause damage. Turn OFF the gas supply before you perform this step.

  1. Set the engine control to the OFF/RESET position.

  2. Thoroughly inspect the 2-pin connectors for the internal ignition harness and the transformer. Refer to Troubleshooting, "Inspecting Electrical Connectors".

  3. Connect the internal ignition harness to the transformer.

  4. Set the engine control to the START position and observe the "Active Diagnostic" screen of Cat ET while you crank the engine.

  5. If the -6 code is generated again, Set the engine control to the OFF/RESET position. Replace the transformer. Make sure that you use the correct transformer for the G3500 A3 Engine.

  6. Clear all of the logged diagnostic codes.

  STOP

• Not OK - A -5 code was not generated for the circuit with the disconnected transformer. The short circuit is in the internal ignition harness.

  Repair: Perform the following steps:

  1. Set the engine control to the OFF/RESET position.

  2. Remove the camshaft covers from the bank of the engine with the suspect cylinder.

  3. Inspect the internal ignition harness for abrasion, exposed wires, or other damage. Repair the harness, when possible. Replace the harness, if necessary.

  STOP