Electronic Modular Control Panel II (EMCP II) Caterpillar

Pulse Width Modulated Sensor

Usage:

System Operation Description:

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

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Illustration 2	g00686791
System Schematic For Engine Coolant Loss Sensor (ECLS)

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Illustration 3	g00527377
System Schematic For Engine Coolant Temperature Sensor (ECTS)

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Illustration 4	g00288430
Pulse Width Modulated Signal

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

oil pressure sensor
coolant temperature sensor
engine coolant loss 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⁾
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%.

Test Step 1. PERFORM INITIAL PREPARATIONS.

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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. However, the DC voltages are listed in the Sensor Specifications chart 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.

Locate the suspect sensor.

Identify the sensor wires and connector contacts. See the preceding System Schematics.

DO NOT DISCONNECT ANY HARNESS CONNECTORS AT THIS TIME.

Use the 7X-1710 Multimeter Probe in order to make future measurements by probing through the back of the harness connectors.

Results:

Continue to the next test step.

Test Step 2. CHECK SENSOR SUPPLY VOLTAGE.

Turn the engine control switch (ECS) to OFF/RESET. Then, turn the ECS to STOP.

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 Test Step4.
NOT OK AND VOLTS = +BATTERY - The voltage is equal to battery positive. The sensor supply is shorted to battery positive in the engine harness.
Repair: Troubleshoot and repair the engine harness.
Stop.
NOT OK AND VOLTS NOT = +BATTERY - The voltage is not from 7.5 to 8.5 DCV and the voltage is not equal to battery positive. Proceed to Test Step 3.

Test Step 3. CHECK THE STATUS OF THE DIAGNOSTIC CODE.

Observe the GSC display.

Expected Result:

A CID 269 diagnostic code is active.

Results:

OK - A CID 269 diagnostic code is active.
Repair: Go to the procedure in Testing And Adjusting, "Troubleshooting Diagnostic Codes".
Stop.
NOT OK - A CID 269 diagnostic code is NOT active. The harness has failed.
Repair: Troubleshoot and repair the harness.
Stop.

Test Step 4. CHECK THE SENSOR SIGNAL.

The ECS remains in the STOP position.

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.

Make a note of the measurements.

Expected Result:

The measured frequency and duty cycle should agree with the values that are listed in the Sensor Specifications table.

Results:

OK - The measurements agree. The sensor is functioning correctly. Proceed to Test Step 5.
NOT OK - The measurements DO NOT agree. Proceed to Test Step 7.

Test Step 5. CHECK THE SIGNAL AT THE GSC HARNESS CONNECTOR.

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.

Expected Result:

The measured frequency and duty cycle should agree with the values that were measured in the previous Test Step "Check The Sensor Signal".

Results:

OK - The measurements agree. The sensor is functioning correctly. Proceed to Test Step 7.
NOT OK - The measurements DO NOT agree. The harness is defective.
Repair: Troubleshoot and repair the engine harness.
Stop.

Test Step 6. CHECK THE STATUS OF THE DIAGNOSTIC CODE.

Check if sensor diagnostic codes are still active.

Expected Result:

Sensor diagnostic codes are still active.

Results:

OK - Sensor diagnostic codes are still active. The GSC may have failed.
Repair: It is unlikely that the GSC has failed. Exit this procedure and perform this entire procedure again. If the problem remains, replace the GSC. See Testing And Adjusting, "EMCP Electronic Control (Generator Set) - Replace".
Stop.
NOT OK - Sensor diagnostic codes are NOT active.
Repair: check the connectors and wiring. See Testing And Adjusting, "Electrical Connector - Inspect".
Stop.

Test Step 7. CHECK THE ENGINE HARNESS.

Disconnect the engine harness from the sensor.

Disconnect the GSC from the harness.

Check the harness for an open circuit.

Expected Result:

The resistance in the circuit is approximately 5 ohms or less.

Results:

OK - The resistance in the circuit is approximately 5 ohms or less. Proceed to Test Step 8.
NOT OK - The resistance measurement is NOT correct.
Repair: Troubleshoot and repair the engine harness.
Stop.

Test Step 8. CHECK THE ENGINE HARNESS (CONTINUED).

The engine harness remains disconnected from the sensor. And the GSC remains disconnected the harness.

Check the signal wire for a short to battery positive, battery negative and sensor supply.

Expected Result:

The resistance of the circuits is greater than 5000 ohms.

Results:

OK - The resistance measurements are correct. Proceed to Test Step 9
NOT OK - One or more resistance measurements are NOT correct.
Repair: Troubleshoot and repair the engine harness.
Stop.

Test Step 9. CHANGE THE RELATED ENGINE CONDITION AND RETEST.

Change the related engine condition by increasing the temperature or pressure.

At the harness connector for the GSC, measure the voltage between the signal wire and ground.

Expected Result:

For an increase in the temperature or pressure, the voltage increases smoothly.

Results:

OK - The voltage increases smoothly. The sensor is not defective.
Repair: It is likely that the wiring has failed. Troubleshoot the wiring. Exit this procedure and perform the entire procedure again. The problem may be intermittent. Check that the problem is still present.
Stop.
NOT OK - The voltage does not increase, or the increase is not smooth.
Repair: The sensor is defective. Replace the sensor.
Stop.