BASE GP-FUEL FILTER 3438126 - Caterpillar

Width Modulated (PWM) SignalIn addition to CID 100 and CID 110 troubleshooting (see Diagnostic Fault Code chart), you can measure the frequency and duty cycle of sensor signals for accuracy.The Oil Pressure Sensor and the Coolant Temperature Sensor are pulse width (PWM) sensors. They produce a digital signal in which the duty cycle varies as conditions change. Meanwhile, the frequency remains constant. Test Procedure This procedure requires the measurement of the frequency and duty cycle of the sensor signal. Use the 9U-7330 Digital Multimeter for measuring frequency and duty cycle. To measure frequency, turn the rotary switch to AC volts and press the HZ button once. To measure duty cycle, turn the rotary switch to AC volts and press the HZ button twice. The 6V-7070 Digital Multimeter does not measure frequency or duty cycle. However, the DC voltages are listed in the Sensor Specifications chart as an alternative to measuring the frequency and duty cycle. The 6V-7070 Digital Multimeter can be used for DC voltage measurements.1. Locate the suspect sensor. Identify the sensor wires and connector contacts; see the preceding System Schematic. DO NOT DISCONNECT ANY HARNESS CONNECTORS AT THIS TIME. Use the 7X-1710 Cable Probe (Spoons) to make measurements by probing through the back of the harness connectors.2. CHECK SENSOR SUPPLY VOLTAGE - Turn the ECS to OFF/RESET and then to STOP. Measure the sensor supply DC voltage at the sensor connector (from contact A to contact B on the sensor connector). The voltage should measure from 7.5 to 8.5 DCV.* OK; the voltage is from 7.5 to 8.5 DCV. Go to Step 3.* NOT OK; the voltage is equal to battery positive. The sensor supply is shorted to battery positive in the engine harness. Troubleshoot and repair the engine harness. STOP.* NOT OK; the voltage is not from 7.5 to 8.5 DCV and is not equal to battery positive. Observe the GSC display. a. If a CID 269 fault code is active, go to that procedure in the Diagnostic Fault Troubleshooting section. STOP.b. If a CID 269 fault code is NOT active, then the harness is faulty. Troubleshoot and repair the harness. STOP.3. CHECK SENSOR SIGNAL - The ECS remains in the STOP position. Measure the frequency and duty cycle of the signal at the sensor connector (from contact C to contact B of the sensor connector). Make a note of the measurements. The