BREATHER 2270590 - Caterpillar

System Operation Description:The troubleshooting procedures for the diagnostic codes of each pressure sensor are identical. The Engine Control Module (ECM) sends a 5 volt supply to terminal A of each sensor. The sensor common connection is connected to terminal B of each sensor. The signal voltage from terminal C of each sensor is sent to the appropriate terminal at the J2/P2 ECM connector.108-3 Diagnostic Code and High Crankcase PressureSome atmospheric pressure sensors that are located in the engine block actually sense crankcase pressure rather than atmospheric pressure. With this type of installation, crankcase pressure of approximately 14 kPa (2 psi) can cause the 108-3 diagnostic code to be generated.Before you proceed with this test, determine whether the sensor is sensing crankcase pressure or atmospheric pressure.If the sensor is sensing crankcase pressure, connect Caterpillar Electronic Technician (ET) to the ECM and clear the diagnostic code. Do not start the engine. Maintain electrical power to the ECM. Wait at least 30 seconds for generation of the diagnostic code. Slowly wiggle the wiring for the sensor in an attempt to generate an intermittent code.If the 108-3 code is generated, continue with the functional test.If the 108-3 code is not generated, there is either a problem with high crankcase pressure or the code is intermittent, due to a loose connector or damaged wiring.A plugged crankcase breather will cause excessive crankcase pressure. Leakage of the crankshaft seal can occur. Sealing of the piston rings can be lost. This will enable crankcase blowby to further increase the crankcase pressure.If the piston rings do not seal, blowby will increase the crankcase pressure and the problem will become worse. Performance will deteriorate. The engine will have poor combustion. Deposits will build up on the pistons, on the valves, and in the cylinder heads. Downward pumping of the pistons against the increased crankcase pressure will further reduce the performance.Sticking of the pistons will also increase the crankcase pressure. If the problem is not resolved, piston seizure will result. If a problem with a piston is suspected, do not operate the engine. Inspect the cylinder liner for scoring and for scuffing. Replace the piston rings and the cylinder liner, if necessary.To eliminate crankcase pressure as the cause of the 108-3 diagnostic code, inspect the crankcase breather. If the breather is plugged, clean the breather or replace the breather. Make sure that the air passages for the breather's system are clear.To verify that the plugged breather was the problem, operate the engine at a high load for at least 30 seconds. If the code does not recur, return the engine to service.
Illustration 1 g01070462
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Schematic
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Terminal locations at the ECM
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Terminal locations at the sensor connectorTest Step 1. Check for Active +5 V Sensor Supply Diagnostic Codes
Connect the Caterpillar Electronic Technician (ET) to the data link connector.
Turn the keyswitch to the ON position. Wait at least 15 seconds for activation of the diagnostic codes.
Verify if any of the following diagnostic codes are active:
232-3 5 Volt Supply voltage high
232-4 5 Volt