GLASS 3822343 - Caterpillar

Illustration 1 g00315944
Schematic symbol for a typical pulse width modulated sensor (PWM) Note: In addition to these tests, the Caterpillar Monitoring System diagnostics are helpful for troubleshooting sensors. Numeric readout mode shows a numeric value of the information from each sensor input. For a detailed explanation, refer to Systems Operation, "Numeric Readout Mode".When you are testing a sensor, it is necessary to identify the connector contacts and the harness wires. The Electrical System Schematic shows the connector contact numbers and corresponding wire numbers. See the Electrical System Schematic in the Service Manual for the machine.On all machines, the wire numbers and connector contacts are identified by these general rules:
The "+V" wire numbers are from 100 to 199. The "+V" contact corresponds to this wire number.
The ground wire number is between 200 and 299. The ground contact corresponds to this wire number.
The wire number for the signal circuits is from 400 to 499. The signal contact corresponds to this wire number. For an example, see Illustration 1:
The "+V" wire is wire number 113.
The "+V" contact is contact "A".
The ground wire is wire number 201.
The ground contact is contact "B".
The signal wire is wire number 443.
The signal contact is contact "C".
Table 1
Tools Needed    
257-9140     Multimeter     1    
7X-1710     Multimeter Probe Group     1    Test Step 1. TROUBLESHOOT THE SENSORS.Troubleshoot sensor circuits in the following order.
Perform the Diagnostic Function, "Sensor Signal Voltage" procedure. This procedure checks the sensor voltages at the sensor while the circuits remain connected. DISCONNECT NOTHING. Troubleshoot "as is" before disconnecting any circuits. Disconnecting circuits first may alter a poor connection. Proving the original cause of a problem may be difficult or impossible.Expected Result:The Diagnostic Function, "Sensor Signal Voltage" procedure has determined the cause of the problem.Results:
OK - This test step has determined the cause of the problem.STOP
NOT OK - This test step has NOT determined the cause of the problem. Proceed to test step 2.Test Step 2. TROUBLESHOOT THE SENSORS
Perform the Diagnostic Function, "Sensor Dynamic Operation" procedure. This is an additional test. This will test the sensor during actual operating conditions. Expected Result:The Diagnostic Function, "Sensor Dynamic Operation" procedure has determined the cause of the problem.Results:
OK - This test step has determined the cause of the problem.STOP
NOT OK - This test step has NOT determined the cause of the problem.Repair: If the sensor and the harness are correct, it is likely that the main display module has failed. Replace the main display module. See Troubleshooting, "Main Display Module - Replace".STOP