G3516B Engines Caterpillar

Illustration 1	g01071348
Top view (1) Inlets for the turbocharger compressors (2) Turbocharger compressor bypass valves (3) Outlet of the aftercooler

Two turbocharger compressor bypass valves (2) are connected between the outlet of the aftercooler (3) and the inlets for the turbocharger compressors (1). Each valve is activated by a solenoid. Some engines are configured with one turbocharger compressor bypass valve. This troubleshooting procedure applies to both configurations.

When the valves are activated, pressurized air from the aftercooler flows into the intake of the engine. This reduces the boost pressure in the air inlet manifold.

The ECM activates the solenoids for the valves during these conditions:

• Turbocharger surge

• Engine shutdown

Turbocharger Surge - A rapid drop in the output power of the generator can cause the engine's speed to quickly increase. The increased speed of the engine causes the turbochargers to overspeed temporarily. This is called a turbocharger surge. Surging can damage the turbochargers.

The generator's switchgear contains a generator output power sensor. This sensor produces a low voltage signal that indicates the amount of power that is being produced by the generator. The sensor's signal is sent to the ECM. The ECM continuously monitors the signal from the sensor. The ECM responds to a rapid drop in the signal from the sensor by activating the solenoids. The solenoids open the valves.

The valves allow the compressed air/fuel mixture in the aftercooler to flow into the intake of the turbocharger's compressor. This reduces the pressure that is created by the turbocharger's compressor.

Engine Shutdown

Engine shutdown occurs when the output for the fuel control relay is OFF and the engine rpm is above 100. The ECM activates the output for the solenoids until the engine rpm drops to zero. This scavenges any unburned gases in the components of the system during engine shutdown.

A "Turbocharger Compressor Bypass Valve Solenoid" diagnostic code is probably caused by a problem with an electrical connector or a harness. The next likely cause is a problem with a solenoid. The least likely cause is a problem with the ECM.

Logged diagnostic codes provide a historical record. Before you begin this procedure, use the Caterpillar Electronic Technician (ET) to print the logged codes to a file.

This procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the logged codes after the problem is resolved.

Illustration 2	g01071347
Schematic for the compressor bypass valves

Test Step 1. Inspect the Electrical Connectors and Wiring

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Illustration 3	g01076938
(4) Ground strap (5) J2/P2 connectors for the ECM (6) J1/P1 connectors for the ECM (7) 16 amp circuit breaker (8) J10/P10 connector for the harness from the solenoids

1. Set the engine control to the OFF/RESET mode. Switch 16 amp circuit breaker (7) to the OFF position.

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

2. Thoroughly inspect the following connectors:

   • J1/P1 and J2/P2 connectors

   • J10/P10 connectors on the terminal box

   1. Check the torque of the allen head screw for the ECM connectors. The proper torque is 6 ± 1 N·m (55 ± 9 lb in).
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      Illustration 4	g01071377
      Harness side of the P2 connector (P2-6) High side wire for the solenoids (P2-7) Low side wire for the solenoids

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      Illustration 5	g00906760
      Harness side of the P10 connector (P10-A) High side wire for the solenoids (P10-B) Low side wire for the solenoids

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the solenoids.
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      Illustration 6	g01071383
      Right side view (8) Solenoid (9) Connector (10) Valve

   3. Thoroughly inspect connectors (9) for solenoids (8). Verify that the connectors do not have moisture or contamination. Check the harness and wiring for abrasion and for pinch points from each solenoid to the ECM.

Expected Result:

The connectors and terminals are connected properly. The connectors are free of moisture and of corrosion. 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 the Low Side Wire for a Short to the +Battery

1. Disconnect the connectors for both of the solenoids for the turbocharger compressor bypass valves.

2. Disconnect the P1 and P2 connectors.

3. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.
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   Illustration 7	g01071398
   Terminal box (4) Ground strap (P2-7) Low side wire for the solenoids

4. Measure the voltage between terminal P2-7 and ground strap (4).

Expected Result:

The voltage is approximately zero volts.

Results:

• OK - The voltage at terminal P2-7 is approximately zero volts. The low side wire does not have a short circuit to the +Battery. Proceed to Test Step 3.

• Not OK - The voltage at terminal P2-7 is approximately equal to the +Battery voltage. The low side wire has a short circuit to the +Battery. The short circuit could be inside the terminal box or in the engine harness.

  Repair: Repair the connector and/or the harness, when possible. Replace parts, if necessary.

  STOP

Test Step 3. Check the Low Side Wire for a Short to Ground

1. Switch the 16 amp circuit breaker OFF. Set the engine control to the OFF/RESET mode.
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   Illustration 8	g01071471
   Terminal box (1) Jumper wire (P2-7) Low side wire for the solenoids (P1-70) Switched +Battery

2. Install jumper wire (1) between terminals P2-7 and P1-70.

3. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

Expected Result:

The 16 amp circuit breaker does not trip.

Results:

• OK - When the low side wire is connected to the +Battery, the 16 amp circuit breaker does not trip. The low side wire does not have a short to ground. Proceed to Test Step 4.

• Not OK - When the low side wire is connected to the +Battery, the 16 amp circuit breaker trips. The low side wire has a short to ground. The short could be inside the terminal box or in the engine harness.

  Repair: Repair the connector and/or the harness, when possible. Replace parts, if necessary.

  STOP

Test Step 4. Check the Low Side Wire for an Open Circuit

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Illustration 9	g01071446
Right side view (1) Terminal B (2) Harness connector

1. At harness connector (2) for the solenoid on the left side of the engine, measure the voltage between terminal B (1) and the engine block. Record the measurement.

2. At harness connector (2) for the solenoid on the right side of the engine, measure the voltage between terminal B (1) and the engine block. Record the measurement.

Expected Result:

Both of the voltage measurements are approximately equal to the +Battery voltage.

Results:

• OK - Both of the voltage measurements are approximately equal to the +Battery voltage. The low side wire does not have an open circuit. Proceed to Test Step 5.

• Not OK - At least one of the voltage measurements is not approximately equal to the +Battery voltage. The low side wire has an open circuit. The open circuit could be inside the terminal box or in the engine harness.

  Repair: Repair the connector and/or the harness, when possible. Replace parts, if necessary.

  STOP

Test Step 5. Check the High Side Wire for a Short to the +Battery

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Illustration 10	g01071448
Terminal box (4) Ground strap (P2-6) High side wire for the solenoids

1. Measure the voltage between terminal P2-6 and ground strap (4).

Expected Result:

The voltage measurement is approximately zero volts.

Results:

• OK - The voltage measurement at terminal P2-6 is approximately zero volts. The high side wire does not have a short circuit to the +Battery. Proceed to Test Step 6.

• Not OK - The voltage measurement at terminal P2-6 is approximately equal to the +Battery voltage. The high side wire has a short circuit to the +Battery. The short circuit could be inside the terminal box or in the engine harness.

  Repair: Repair the connector and/or the harness, when possible. Replace parts, if necessary.

  STOP

Test Step 6. Check the High Side Wire for a Short to Ground

1. Switch the 16 amp circuit breaker OFF. Set the engine control to the OFF/RESET mode.

2. Remove the end of the jumper wire from terminal P2-7.
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   Illustration 11	g01071460
   Terminal box (1) Jumper wire (P2-6) High side wire for the solenoids (P1-70) Switched +Battery

3. Install the end of jumper wire (1) into terminal P2-6. The jumper wire should be connected between terminals P2-6 and P1-70.

4. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

Expected Result:

The 16 amp circuit breaker does not trip.

Results:

• OK - When the high side wire is connected to the +Battery, the 16 amp circuit breaker does not trip. The high side wire does not have a short to ground. Proceed to Test Step 7.

• Not OK - When the high side wire is connected to the +Battery, the 16 amp circuit breaker trips. The high side wire has a short to ground. The short circuit could be inside the terminal box or in the engine harness.

  Repair: Repair the connector and/or the harness, when possible. Replace parts, if necessary.

  STOP

Test Step 7. Check the High Side Wire for an Open Circuit

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Illustration 12	g01071462
Right side view (1) Harness connector (2) Terminal A

1. At harness connector (1) for the solenoid on the left side of the engine, measure the voltage between terminal A (2) and the engine block. Record the measurement.

2. At harness connector (1) for the solenoid on the right side of the engine, measure the voltage between terminal A (2) and the engine block. Record the measurement.

Expected Result:

Both of the voltage measurements are approximately equal to the +Battery voltage.

Results:

• OK - Both of the voltage measurements are approximately equal to the +Battery voltage. The high side wire does not have an open circuit. Proceed to Test Step 8.

• Not OK - At least one of the voltage measurements is not approximately equal to the +Battery voltage. The high side wire has an open circuit.

  Repair: Repair the connector and/or the harness, when possible. Replace parts, if necessary.

  STOP

Test Step 8. Check the Solenoid on the Left Side of the Engine for a Short Circuit

1. Connect the connector for the solenoid on the left side of the engine. Listen for an audible click from the solenoid as the connector is connected.

   If the ambient noise is too loud, touch the solenoid when the connector is connected in order to feel the vibration. The solenoid will vibrate when the connector is connected.

Expected Result:

The solenoid does not energize.

Results:

• OK - When the solenoid on the left side of the engine is connected, the solenoid does not energize. The solenoid does not have an internal short circuit.

  Repair: Disconnect the harness connector for the solenoid on the left side of the engine.

  Proceed to Test Step 9.

• Not OK - When the solenoid on the left side of the engine is connected, the solenoid energizes. The solenoid has an internal short circuit.

  Repair: Replace the turbocharger compressor bypass valve on the left side of the engine.

  STOP

Test Step 9. Check the Solenoid on the Right Side of the Engine for a Short Circuit

1. Connect the harness connector for the solenoid on the right side of the engine. Listen for an audible click from the solenoid as the connector is connected.

   If the ambient noise is too loud, touch the solenoid when the connector is connected in order to feel the vibration. The solenoid will vibrate when the connector is connected.

Expected Result:

The solenoid does not energize.

Results:

• OK - When the solenoid on the right side of the engine is connected, the solenoid does not energize. The solenoid does not have an internal short circuit.

  Repair: Disconnect the harness connector for the solenoid on the right side of the engine.

  Proceed to Test Step 10.

• Not OK - When the solenoid on the left side of the engine is connected, the solenoid energizes. The solenoid has an internal short circuit.

  Repair: Replace the turbocharger compressor bypass valve on the left side of the engine.

  STOP

Test Step 10. Check the Solenoid on the Left Side of the Engine for an Open Circuit

1. Switch the 16 amp circuit breaker OFF. Set the engine control to the OFF/RESET mode.
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   Illustration 13	g01071466
   Terminal box (1) Jumper wire (P2-7) Low side wire for the solenoids (P1-65) -Battery

2. Install a jumper wire between terminals P2-7 and P1-65.

3. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

4. Connect the connector for the solenoid on the left side of the engine. Listen for an audible click from the solenoid as the connector is connected.

   If the ambient noise is too loud, touch the solenoid when the solenoid is connected in order to feel the vibration. The solenoid will vibrate when the connector is connected.

Expected Result:

The solenoid is energized when the solenoid's connector is connected.

Results:

• OK - When the connector for the solenoid on the left side of the engine is connected, the solenoid is energized. The solenoid does not have an open circuit. Proceed to Test Step 11.

• Not OK - When the connector for the solenoid on the left side of the engine is connected, the solenoid is not energized. The solenoid has an open circuit.

  Repair: Replace the turbocharger compressor bypass valve on the left side of the engine.

  STOP

Test Step 11. Check the Solenoid on the Right Side of the Engine for an Open Circuit

1. Connect the connector for the solenoid on the right side of the engine. Listen for an audible click from the solenoid as the connector is connected.

   If the ambient noise is too loud, touch the solenoid when the solenoid is connected in order to feel the vibration. The solenoid will vibrate when the connector is connected.

Expected Result:

The solenoid is energized when the solenoid's connector is connected.

Results:

• OK - When the connector for the solenoid on the right side of the engine is connected, the solenoid is energized. The solenoid does not have an open circuit.

  Repair: Perform the following procedure:

  1. Switch the 16 amp circuit breaker OFF. Set the engine control to the OFF/RESET mode.

  2. Remove the two jumper wires from the P1 and P2 connectors.

  3. Reconnect the P1 and P2 connectors.

  Proceed to Test Step 12.

• Not OK - When the connector for the solenoid on the right side of the engine is connected, the solenoid is not energized. The solenoid has an open circuit.

  Repair: Replace the turbocharger compressor bypass valve on the left side of the engine.

  STOP

Test Step 12. Check for Diagnostic Codes

1. Start the engine and run the engine to high idle.

2. Stop the engine.

Expected Result:

Neither of the following diagnostic codes are activated:

• 1720-05 Turbo Compressor Bypass Valve Solenoid open

• 1720-06 Turbo Compressor Bypass Valve Solenoid shrt to gnd

Results:

• OK - When the engine was shut down, no diagnostic codes were activated for the solenoids. The problem appears to be resolved. The problem may have been caused by a poor electrical connection.

  STOP

• Not OK - When the engine was shut down, a diagnostic code was activated for the solenoids. The ECM may have a problem.

  Repair: It is unlikely that the ECM has failed. Perform this entire procedure again. If the problem is not resolved, 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 original ECM. Refer to Troubleshooting, "Replacing the ECM".

  STOP