938G Wheel Loader, 938G Series II Wheel Loader, IT38G Integrated Toolcarrier and IT38G Series II Integrated Toolcarrier Traction Control System Proportional Pressure Solenoid Valve - Test Caterpillar

Illustration 1	g00280988
Proportional Pressure Solenoid Valves

The proportional pressure solenoid valves are located behind the ladder on the left side of the machine.

Testing

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Make reference to the WARNINGS on the first several pages of the Testing And Adjusting section.

Perform the following procedure if the service codes do not provide enough information in order to find the problem.

Note: Use AVS ET to view active service codes.

Before you perform any tests, attempt to isolate the malfunctioning solenoid valve by using the Traction Control System test mode. This can determine whether a solenoid valve is providing the proper pressure to a specific wheel brake. Use the following procedure to isolate a malfunctioning solenoid valve.

1. Move the machine to an open, level area with stable ground conditions.

2. Put the transmission into second speed forward and place the TCS test/enable switch in the Test position.

   Note: The test time is approximately five seconds.

3. While the machine is moving at half throttle, turn the machine to the right or to the left.

4. The Traction Control System (TCS) will attempt to repeatedly apply the brakes of the wheels that are on the outside of the turn. Watch for a wheel that does not behave in the same manner as the other wheels. For example, the right front brake and the right rear brake should cycle on and off during a left turn.

When the brake is applied during this procedure, you should be able to detect a small amount of wheel slip.

Note: After the malfunctioning solenoid valve has been isolated, perform the following test.

Hydraulic Test Procedure

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Make reference to the WARNINGS on the first several pages of the Testing And Adjusting section.

Testing with a Service Code Plug

1. Stop the engine.

2. Remove the air purge screw at the brake that corresponds to the malfunctioning solenoid valve.

3. Attach the pressure gauge at the air purge screw location.

4. Remove the standard harness code plug from the machine harness. Install the service code plug for bleeding the brakes.

5. Start the engine.

6. Place the TCS Test/Enable switch in either of the Enable positions.

7. All four solenoids will be energized with a current that will supply approximately 1600 kPa (230 psi) of pressure to the brakes. Measure the pressure at the wheel brake and compare the pressure to the output of the solenoid valve. The output should be 1600 ± 260 kPa (230 ± 38 psi).

If the solenoid valve does not meet the specifications, continue with the following test. If the solenoid valve is within the specifications, perform the procedure for the test mode again in order to check for a solenoid valve that is operating abnormally.

Testing with Electronic Technician (ET)

Reference: Testing and Adjusting, "Using Cat ET Software To Determine Service Codes" for a complete list of the components needed to use Cat ET on the machine.

1. Stop the engine.

2. Remove the air purge screw at the brake that corresponds to the malfunctioning solenoid valve.

3. Attach the pressure gauge at the air purge screw location.

4. Connect AVS ET to the service connector.

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Illustration 2	g00282338
The service connector is located behind the panel.

5. Start the engine.

6. Place the TCS Test/Enable switch in either of the Enable positions.

7. AVS ET offers three different tests for bleeding the brakes.

   Select "Diagnostic".

   Select "Diagnostic Tests".

   Select "Brake Test".

Illustration 3	g00281003
Typical display diagnostics screen for brakes

The following three tests can be performed by using the selection menus at the bottom of the display diagnostics screen:

• "Bleed" (1600 kPa (230 psi)).

• "Ramp" (400 kPa (58 psi) to 3445 kPa (500 psi)).

• "Step" (400 kPa (58 psi) to 3445 kPa (500 psi))

If the solenoid valve does not meet the specifications, continue with the test that follow. If the solenoid valve is within the specifications, perform the test procedure with AVS ET again in order to check for a solenoid valve that is operating abnormally.

Electrical Test Procedure

The following materials are necessary to perform this test:

• 140-7862 Brake Air Purge Plug

• 6V-7070 Digital Multimeter Group

• 7000 kPa (1015 psi) pressure gauge

• Test harness

Illustration 4	g00281015
Test Harness

The parts necessary to build a test harness are as follows:

1. Remove the air purge screw at the brake with the faulty solenoid valve.

2. Attach the pressure gauge at the air purge screw location.

3. Make sure that there are no blockages in the brake line. Start the engine and run the engine at full rpm. Apply the service brakes. The pressure gauge should read 6900 ± 350 kPa (1000 ± 50 psi).

4. Stop the engine.

5. Remove the standard harness code plug from the machine harness. Install the brake air purge plug.

6. Disconnect the harness at the faulty solenoid valve. Connect the test harness in series with the solenoid valve and the machine harness.

7. Connect multimeter probes (11) of the test harness to the "COM" terminal and the "+DC" terminal of the multimeter.

8. Start the engine.

9. Place the TCS Test/Enable switch in either of the Enable positions.

10. Measure the voltage with the multimeter. The voltage should be 0.05 ± 0.02 DCV.

11. If the voltage is not correct, check the machine harness and the traction control system (TCS) ECM.

12. If the voltage is correct but there is no pressure, stop the engine and remove the coil from the solenoid valve. Check the resistance of the coil. The resistance should be 10 ± 2 ohms.

13. If the coil has the correct resistance, replace the cartridge assembly of the solenoid valve.