Caterpillar Monitoring System for Electronic Modular Control Panel Caterpillar

General Information

Illustration 1	g00315944
Typical Schematic For Pulse Width Modulated Sensor (PWM)

Note: In addition to these tests, the Caterpillar Monitoring System diagnostics are helpful when you are 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 engine.

On all engines, the wire numbers and connector contacts are identified by these general rules:

• The wire number for the +V is between 100 and 199. The contact for +V 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 wire is between 400 and 499. The signal contact corresponds to this wire number.

For an example, see Illustration 1:

• The wire for +V is wire number 113.

• The contact for +V 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".

Procedure

1. Troubleshoot the sensors.

   Troubleshoot sensor circuits in the following order.

   1. Perform the "Sensor Signal Voltage Tests". The test checks the voltages of the sensor. The test is at the sensor and all of the circuits are connected. DISCONNECT NOTHING. Troubleshoot "as is" before you disconnect any circuits. Disconnecting circuits first may alter a poor connection. Proving the original cause of a problem may be difficult or impossible.

   2. The "Sensor Dynamic Test" is an alternate test. This test measures the sensor during actual operating conditions. Run this test if it is necessary.

   3. If the sensor and the harness are correct, it is likely that the main display module is faulty. Replace the main display module and see Testing and Adjusting, "Module - Replace".

To identify the sensor wires and connector contacts, see "General Information". Otherwise proceed to Testing and Adjusting, "Sensor Signal Voltage - Test".