Electronic Modular Control Panel II+ (EMCP II+) for EUI Engines Caterpillar

Pulse Width Modulated (PWM) Sensor - Test

Usage:

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Illustration 1	g00537438
System Schematic For Engine Oil Pressure Sensor (EOPS)

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Illustration 2	g00527377
System Schematic For Engine Coolant Temperature Sensor (ECTS)

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Illustration 3	g00529671
System Schematic For Engine Oil Temperature Sensor (EOTS)

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Illustration 4	g00288430
Pulse Width Modulated Signal

This test is provided in addition to the CID 100, CID 110 and CID 175 troubleshooting procedures. See Testing And Adjusting, "Troubleshooting Diagnostic Codes". The pulse width modulated sensors are listed below.

oil pressure sensor
coolant temperature sensor
oil temperature sensor

These PWM sensors produce a digital signal. In a digital signal, the duty cycle varies as the condition changes. The frequency remains constant.

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Table 1
Sensor Specifications
Engine Oil Pressure Sensor (EOPS) ⁽¹⁾
Pressure kPa (psi)	Signal Voltage ⁽²⁾ DCV	Signal Duty Cycle ⁽²⁾ %
0 to 69 (0 to 10)	0.92 to 1.44	12.8 to 20.8
69 to 138 (10 to 20)	1.44 to 1.92	20.8 to 28.1
138 to 207 (20 to 30)	1.92 to 2.40	28.1 to 35.4
207 to 276 (30 to 40)	2.40 to 2.89	35.4 to 42.6
276 to 345 (40 to 50)	2.89 to 3.34	42.6 to 49.6
345 to 414 (50 to 60)	3.34 to 3.89	49.6 to 56.6
414 to 483 (60 to 70)	3.89 to 4.29	56.6 to 64.0
483 to 552 (70 to 80)	4.29 to 4.74	64.0 to 70.5
552 to 621 (80 to 90)	4.74 to 5.25	70.5 to 78.1
621 to 690 (90 to 100)	5.25 to 5.74	78.1 to 85.0

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^( 1 )	The base frequency is 350 to 650 Hz.
^( 2 )	The voltages and currents are guidelines for troubleshooting and are not considered exact. Tolerance is ±10%.

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Table 2
Sensor Specifications
Engine Coolant Temperature Sensor (ECTS) ⁽¹⁾ And Engine Oil Temperature Sensor (EOTS) ⁽¹⁾
Temperature °C (°F)	Signal Voltage ⁽²⁾ DCV	Signal Duty Cycle ⁽²⁾ %
-40 to -29 (-40 to -20)	1.18 to 1.23	10.0 to 10.6
-29 to -18 (-20 to 0)	1.23 to 1.30	10.6 to 11.6
-18 to -7 (0 to 20)	1.30 to 142	11.6 to 13.3
-7 to 4 (20 to 40)	1.42 to 1.63	13.3 to 16.2
4 to 16 (40 to 60)	1.63 to 1.97	16.2 to 21.1
16 to 27 (60 to 80)	1.97 to 2.43	21.1 to 27.5
27 to 38 (80 to 100)	2.43 to 3.00	27.5 to 35.6
38 to 49 (100 to 120)	3.00 to 3.67	35.6 to 45.0
49 to 60 (120 to 140)	3.67 to 4.35	45.0 to 54.7
60 to 71 (140 to 160)	4.35 to 5.00	54.7 to 63.9
71 to 82 (160 to 180)	5.00 to 5.58	63.9 to 72.0
82 to 93 (180 to 200)	5.58 to 6.05	72.0 to 78.6
93 to 104 (200 to 220)	6.05 to 6.42	78.6 to 83.8
104 to 116 (220 to 240)	6.42 to 6.72	83.8 to 88.1
116 to 125 (240 to 257)	6.72 to 6.90	88.1 to 90.6
125 to 135 (257 to 275)	6.90 to 7.05	90.6 to 92.7

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^( 1 )	The Base frequency is 370 to 550 Hz.
^( 2 )	The voltages and currents are guidelines for troubleshooting and are not considered exact. Tolerance is ±10%.

The engine coolant temperature sensor and the engine oil temperature sensor are the same Caterpillar part. The only difference is the application of the part. Both of the sensor's specs are identical.

Test Procedure

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Table 3
Tools Needed
9U-7330	Multimeter Multimeter is optional for frequency and duty cycle measurements.	1
7X-170	Multimeter Probe Group	1
146-4080	Digital Multimeter (RS-232)	1

This procedure requires the measurement of the frequency and duty cycle of the sensor signal. Use the 9U-7330 Digital Multimeter in order to measure the frequency and the duty cycle. In order to measure frequency, turn the rotary switch to AC volts. Then, press the "HZ" button once. In order to measure the duty cycle, turn the rotary switch to AC volts and press the "HZ" button twice.

Note: The 6V-7070 Digital Multimeter does not measure the frequency or the duty cycle. The DC voltages are listed in Table 2 as an alternative to measuring the frequency and the duty cycle. The 6V-7070 Digital Multimeter can be used for measurements of the DC voltage.

Perform Initial Preparations.
1. Locate the suspect sensor.
1. Identify the sensor wires and connector contacts. See the preceding System Schematics.
1. DO NOT DISCONNECT ANY HARNESS CONNECTORS AT THIS TIME.
1. Use the 7X-1710 Multimeter Probe in order to make future measurements by penetrating through the back of the harness connectors.

Check Sensor Supply Voltage.
1. Turn the engine control switch (ECS) to OFF/RESET. Then, turn the ECS to STOP.
1. Measure the sensor supply voltage at the sensor connector. Perform the measurement from contact "A" to contact "B" on the sensor connector.
  Expected Result: The voltage should be from 7.5 to 8.5 DCV.
  Results:
  - OK: The voltage is from 7.5 to 8.5 DCV. Proceed to Step 4.
  - 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 the voltage is not equal to battery positive. Proceed to Step 3.

Check The Status Of The Fault.
Observe the GSC+ display.
Expected Result: A CID 269 fault code is active.
Results:
- OK: A CID 269 fault code is active. Go to the procedure in Testing And Adjusting, "Troubleshooting Diagnostic Codes". STOP.
- NOT OK: A CID 269 fault code is NOT active. The harness is faulty. Troubleshoot and repair the harness. STOP.

Check The Sensor Signal.
The ECS remains in the STOP position.
1. Measure the frequency and the duty cycle of the signal at the sensor connector. Conduct the measurements from contact "C" to contact "B" of the sensor connector.
1. Make a note of the measurements.
  Expected Result: The frequency that is measured should agree with the values that are listed in the Sensor Specifications chart and the duty cycle should agree with the values that are listed in the Sensor Specifications chart.
  Results:
  - OK: The measurements agree. The sensor is functioning correctly. Proceed to Step 5.
  - NOT OK: The measurements DO NOT agree. Proceed to Step 7.

Check The Signal At The GSC+ Harness Connector.
1. Measure the frequency and the duty cycle of the signal at the GSC+ harness connector.
  - For the oil pressure signal, measure the resistance from contact 8 to contact 31.
  - For the coolant temperature signal, measure the resistance from contact 7 to contact 31.
  - For the oil temperature signal, measure the resistance from contact 14 to contact 31.
  Expected Result: The measured frequency should agree with the values that were measured in Step 4. The duty cycle should agree with the values that were measured in Step 4.
  Results:
  - OK: The measurements agree. The sensor is functioning correctly. Proceed to Step 7.
  - NOT OK: The measurements DO NOT agree. The harness is faulty. Troubleshoot and repair the engine harness. STOP.

Check The Status Of The Fault.
1. Check if sensor fault codes are still active.
  Expected Result: Sensor fault codes are still active.
  Results:
  - OK: The GSC+ is faulty. Replace the GSC+. See Testing And Adjusting, "EMCP Electronic Control (Generator Set) - Replace". STOP.
  - NOT OK: If sensor fault codes are NOT active, check the connectors and wiring. See Testing And Adjusting, "Electrical Connector - Inspect". STOP.

Check The Engine Harness.
1. Disconnect the engine harness from the sensor.
1. Disconnect the GSC+ from the harness.
1. Check the harness for an open circuit. A correct circuit will be approximately 5 ohms or less.
1. Check the signal wire for a short to battery positive, battery negative and sensor supply. A correct circuit will be greater than 5000 ohms.
  Expected Result: For Step 7.c, the resistance should be 5 ohms or less. For Step 7.d, the resistance should be greater than 5000 ohms.
  Results:
  - OK: All resistance measurements are correct. Therefore, replace the sensor. STOP.
  - NOT OK: One or more resistance measurements are NOT correct. Troubleshoot and repair the engine harness. STOP.