GUARD AS 6Y9949 - Caterpillar

Illustration 5 g01389161
Terminals at the customer connector that are associated with the auxiliary pressure sensor
(14) Sensor supply
(15) Sensor return
(33) Auxiliary pressure (if equipped)
Illustration 6 g01159881
Terminal locations at the sensor connector
(Terminal A) Sensor supply
(Terminal B) Sensor return
(Terminal C) Signal
The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere.
Test Step 1. Determine if the Code is Logged or Active
Connect Cat ET to the service tool connector.
Restore electrical power to the engine ECM.
Monitor the active diagnostic code and the logged diagnostic codes on Cat ET. Note: Wait at least 30 seconds in order for diagnostic codes to become active.Identify the diagnostic code.Results:
Logged code - Repair: Do not troubleshoot a logged code unless the code relates to an operator complaint. If the code is logged and the code does not relate to an operator complaint, clear the code.If the code is logged and the code relates to an operator complaint, check the integrity of the connections at the connectors.STOP
Active code - Proceed to Test Step 2.Test Step 2. Check the Supply Voltage at the Sensor ConnectorMeasure the voltage between terminal A (sensor supply) and terminal B (sensor return) at the harness connector for the sensor that relates to the code.Expected Result:The voltage is between 4.5 VDC and 5.5 VDC.Results:
OK - The voltage is between 4.5 VDC and 5.5 VDC. The supply voltage is at the sensor connector. Record the voltage measurement. If you are troubleshooting a -3 diagnostic code, proceed to Test Step 3. If you are troubleshooting a -4 diagnostic code, proceed to Test Step 6.
Not OK - The voltage is less than 4.5 VDC or the voltage is greater than 5.5 VDC.Repair: The voltage of the sensor supply is incorrect. Refer to Troubleshooting, "Sensor Supply - Test".STOPTest Step 3. Check for Battery Voltage on the Signal WireMeasure the voltage between the signal terminal and the return terminal on the harness connector for the sensor that relates to the diagnostic code.Expected Result:The voltage measurement is less than the +Battery voltage.Results:
OK - The voltage measurement is less than the +Battery voltage. The signal wire is not shorted to the +Battery. Proceed to Test Step 4.
Not OK - The voltage measurement is approximately equal to the +Battery voltage. The signal wire is shorted to the +Battery.Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.STOPTest Step 4. Check the Signal Wire for an Open Circuit
Disconnect the sensor that relates to the diagnostic code.
Connect a jumper wire between the signal terminal and the return terminal on the harness connector for the sensor that relates to the diagnostic code. This will replace the sensor with a short circuit.
Look for a -4 diagnostic code. Expected Result:The -3 code does not change to a -4 code