The analog sensor supply provides power to all analog sensors. The Electronic Control Module (ECM) supplies 5.0 ± 0.2 VDC to each analog sensor connector. The analog sensor supply is output short circuit protected. A short circuit to the battery will not damage the circuit inside the ECM.
Note: The analog sensors are not protected from overvoltage. A short from the analog supply line to the +Battery supply may damage the sensors. If CID-FMI 262-03 is logged, it is possible that all of the analog sensors have been damaged. Repair the analog sensor supply and check for any "ACTIVE" sensor diagnostic codes in order to determine if a sensor has failed.
Note: You can use the Caterpillar Electronic Technician (ET) in order to monitor various parameters:warnings, derates, shutdown override setpoints and delay times. Parameters may affect the behavior of the ECM. The behavior of the ECM may vary from the description that is given in this system operation section.
The following list contains a description of the analog sensors that are found on the engine.
Coolant Temperature Sensor - Cold mode operation improves the engine starting ability. Cold mode operation helps to control white smoke during cold starts. Cold mode operation helps to improve warm up time of the engine. In normal mode, injection timing is varied as a function of engine speed and load. The process of combustion is improved by controlling the injection timing in cold mode. Transient engine response is slower in cold mode operation. Cold mode operation is activated when the engine water temperature is below 60 °C (140 °F). Cold mode operation will remain active until water temperature rises above 63 °C (145 °F). The engine will alternate between cold mode and normal mode during operation, as engine temperature fluctuates. The operating range of the sensor is -40 °C to 120 °C (-40 °F to 248 °F).
Filtered Fuel Pressure Sensor - The sensor is used in conjunction with the unfiltered fuel pressure sensor to determine the restriction across the fuel filters. The sensor output is a DC voltage that varies with filtered fuel pressure between 0.2 VDC and 4.8 VDC. The sensor is located on the end cap of the fuel filter housing. The operating range of the sensor is 0.0 kPa to 1090 kPa (0.0 psi to 158 psi). The ECM calibrates the sensor within the first five seconds after power is applied to the ECM. The ECM checks the sensor value against an acceptable pressure range. If the pressure value is not in this range, the previous calibration will be used. A manual calibration of the sensor should be done if the sensor or the ECM has been replaced. Perform the calibration procedure Troubleshooting, "Anolog Sensor - Calibrate".
Unfiltered Fuel Pressure Sensor - The sensor is used in conjunction with the filtered fuel pressure sensor to determine the restriction across the fuel filters. The sensor output is a DC voltage that varies with unfiltered fuel pressure between 0.2 VDC and 4.8 VDC. The sensor is located on the end cap of the fuel filter housing. The operating range of the sensor is 0.0 kPa to 1090 kPa (0.0 psi to 158 psi). The ECM calibrates the sensor within the first five seconds after power is applied to the ECM. The ECM checks the sensor value against an acceptable pressure range. If the pressure value is not in this range, the previous calibration will be used. A manual calibration of the sensor should be done if the sensor or the ECM has been replaced. Perform the calibration procedure Troubleshooting, "Anolog Sensor - Calibrate".
Filtered Engine Oil Pressure Sensor - The sensor is used in conjunction with the unfiltered engine oil pressure sensor in order to determine the restriction across the engine oil filters. The ECM uses this sensor to detect low engine oil pressure which may indicate a failed engine oil pump or low engine oil pressure. The signal is compared with a map of engine oil pressure versus engine rpm which is stored in the ECM. The sensor output is a DC voltage that varies with engine oil pressure between 0.2 VDC and 4.8 VDC. The sensor is located downstream of the engine oil filter. The operating range of the sensor is 0.0 kPa to 1090 kPa (0.0 psi to 158 psi). The ECM calibrates the sensor within the first five seconds after power is applied to the ECM. The ECM checks the sensor value against an acceptable pressure range. If the pressure value is not in this range, the previous calibration will be used. A manual calibration of the sensor should be done if the sensor or the ECM has been replaced. Perform the calibration procedure Troubleshooting, "Anolog Sensor - Calibrate".
Unfiltered Engine Oil Pressure Sensor - The sensor is used in conjunction with the filtered engine oil pressure sensor to determine the restriction across the engine oil filters. The sensor output is a DC voltage that varies with unfiltered engine oil pressure between 0.2 VDC and 4.8 VDC. The sensor is located before the engine oil filters in the oil passage of the engine oil filter housing. The operating range of the sensor is 0.0 kPa to 1090 kPa (0.0 psi to 158 psi). The ECM calibrates the sensor within the first five seconds after power is applied to the ECM. The ECM checks the sensor value against an acceptable pressure range. If the pressure value is not in this range, the previous calibration will be used. A manual calibration of the sensor should be done if the sensor or the ECM has been replaced. Perform the calibration procedure Troubleshooting, "Anolog Sensor - Calibrate".
Turbocharger Compressor Inlet Pressure Sensor - The sensor is used in conjunction with the atmospheric pressure sensor to determine if the engine air filter is plugged. The sensor indicates if the left turbocharger compressor inlet has a restriction. The sensor output is a DC voltage between 0.2 VDC and 4.8 VDC that varies with left turbocharger compressor inlet pressure. The operating range of the sensor is 0.0 kPa to 111 kPa (0.0 psi to 16 psi). The ECM calibrates the sensor within the first five seconds after power is applied to the ECM. The ECM checks the sensor value against an acceptable pressure range. If the pressure value is not in this range, the previous calibration will be used. A manual calibration of the sensor should be done if the sensor or the ECM has been replaced. Perform the calibration procedure Troubleshooting, "Anolog Sensor - Calibrate".
Turbocharger Compressor Outlet Pressure Sensor - The sensor is used to obtain boost pressure. Boost pressure is used to control the ratio of fuel to air during acceleration. The ECM limits the amount of fuel that is injected, based upon inlet manifold pressure. Information in the ECM defines the relationship between the manifold pressure and the fuel ratio control limit (FRC). The operation is similar to the fuel ratio control on an engine with a mechanical governor. The sensor output is a DC voltage between 0.2 VDC and 4.8 VDC that varies with turbocharger outlet pressure. The operating range of the sensor is 0.0 kPa to 452 kPa (0.0 psi to 65 psi). The ECM calibrates the sensor within the first five seconds after power is applied to the ECM. The ECM checks the sensor value against an acceptable pressure range. If the pressure value is not in this range, the previous calibration will be used. A manual calibration of the sensor should be done if the sensor or the ECM has been replaced. Perform the calibration procedure Troubleshooting, "Anolog Sensor - Calibrate".
Atmospheric Pressure Sensor - The sensor is used to provide an atmospheric pressure signal to the ECM. If the atmospheric pressure sensor should fail, the turbocharger compressor inlet pressure sensor is used as a substitute. The sensor output is a DC voltage between 0.2 VDC and 4.8 VDC that varies with atmospheric pressure. The operating range of the sensor is 0.0 kPa to 111 kPa (0.0 psi to 16 psi). The sensor is used to calibrate the other pressure sensors within the first five seconds after power is applied to the ECM. The ECM checks the sensor value against an acceptable pressure range. If the pressure value is not in this range, a diagnostic message will be generated and the engine may be derated. A manual calibration of the sensor should be done if the sensor or the ECM has been replaced. Perform the calibration procedure Troubleshooting, "Anolog Sensor - Calibrate".
Crankcase Pressure Sensor - The sensor is used in conjunction with the atmospheric pressure sensor to determine if the engine crankcase pressure is too high. The atmospheric pressure is subtracted from the absolute crankcase pressure. The difference between the atmospheric pressure and the absolute crankcase pressure is the differential crankcase pressure. The sensor output is a DC voltage between 0.2 VDC and 4.8 VDC that varies with crankcase pressure. The operating range of the sensor is 0.0 kPa to 111 kPa (0.0 psi to 16 psi). The ECM calibrates the sensor within the first five seconds after power is applied to the ECM. The ECM checks the sensor value against an acceptable pressure range. If the pressure value is not in this range, the previous calibration will be used. A manual calibration of the sensor should be done if the sensor or the ECM has been replaced. Perform the calibration procedure Troubleshooting, "Anolog Sensor - Calibrate".
Aftercooler Temperature Sensor - The ECM uses the signal from the sensor to monitor changes in system temperature. The ECM makes adjustments to the system's operating parameters as the temperature changes. This allows the engine to operate at optimal performance through a wide range of operating temperatures. The operating range of the sensor is -40 °C to 120 °C (-40 °F to 248 °F).
"Tandem Engine Coupling Oil Pressure Sensor" - The master ECM uses the signal from the sensor to monitor oil pressure within the coupling. The operating range of the sensor is 0.0 kPa to 1135 kPa (0.0 psi to 165 psi). The signal voltage at 204.8 kPa (29.7 psi) should be 0.95 VDC. The signal voltage at 965.3 kPa (140 psi) should be 4.26 VDC.
Note: The circuit for the front engine begins with the letter T. The circuit for the rear engine begins with the letter R.
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| Illustration 1 | g00784683 |
Typical schematic | |
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| Illustration 2 | g00947988 |
Typical schematic | |
Test Step 1. Check for Connector Damage.
- Turn the circuit breaker for the battery to the OFF position.
- Turn the keyswitch to the OFF position.
- Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
- Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
- Check the ECM connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).
- Check the customer connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).
- Check the harness and the wiring for abrasion and for pinch points.
Expected Result:
All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion or of pinch points.
Results:
- OK - The connectors and wiring are okay. Proceed to Test Step 2.
- Not OK - The connectors and/or wiring are not okay.
Repair: Repair the connectors and/or wiring or replace the connectors and/or wiring.
Stop.
Test Step 2. Check for a Short Circuit in the Harness.
- If the problem is with the analog supply for the front engine or for the rear engine, disconnect ECM connector J1/P1. If the problem is with the analog supply for the master ECM, disconnect ECM connector J2/P2.
- Disconnect all of the analog sensors.
- Measure the resistance between the analog supply pin 36 and the analog return pin 30.
- Measure the resistance between the analog supply pin 36 and the engine ground.
- Measure the resistance between the analog return pin 30 and the engine ground.
Expected Result:
The resistance is more than 20,000 Ohms for each measurement.
Results:
- OK - The resistance is greater than 20,000 Ohms. Proceed to Test Step 3.
- Not OK - The resistance is less than 20,000 Ohms.
Repair: Repair the connectors and/or wiring or replace the connectors and/or wiring.
Stop.
Test Step 3. Check the Analog Sensor Supply Voltage at the ECM.
- Remove the wire that is in pin 36 from the ECM connector. Install a wire jumper into the socket for pin 36.
- Remove the wire that is in pin 30 from the ECM connector. Install a wire jumper into the socket for pin 30.
Note: If you remove the sensor common from the ECM, an open circuit diagnostic code will be generated for all sensors that use the sensor common. Troubleshoot the original code. Delete the logged diagnostic codes when you are finished.
- Reconnect the ECM connector.
- Turn the circuit breaker for the battery to the ON position.
- Turn the keyswitch to the ON position. The engine should be off.
- Measure the voltage between the wire jumpers in pin 36 and pin 30.
- Turn the keyswitch to the OFF position.
- Remove the jumper wires and reconnect the wires that were in pin 36 and in pin 30.
- Reconnect the ECM connector.
Expected Result:
The supply voltage is 5.0 ± 0.2 VDC.
Results:
- OK - The supply voltage is 5.0 ± 0.2 VDC. Proceed to Test Step 4.
- Not OK - The supply voltage is not 5.0 ± 0.2 VDC.
Repair: The supply voltage is not correct at the ECM. Perform the diagnostic functional test Troubleshooting, "Electrical Power Supply".
Stop.
Test Step 4. Check the Analog Sensor Supply Voltage at the Sensor Connector.
- Turn the keyswitch to the ON position. The engine should be off.
- Measure the voltage between socket A and socket B on the harness side of all analog sensor connectors. Ensure that you are measuring on the harness side of the connector since the sensors are disconnected.
- Turn the keyswitch to the OFF position.
Expected Result:
The supply voltage is 5.0 ± 0.2 VDC.
Results:
- OK - The supply voltage is 5.0 ± 0.2 VDC. Proceed to Test Step 5.
- Not OK - The supply voltage is not 5.0 ± 0.2 VDC. There is an open circuit in the harness or connectors.
Repair: Repair the connectors and/or wiring or replace the connectors and/or wiring.
Stop.
Test Step 5. Check the Analog Sensors for Short Circuits.
- Connect the analog sensor. Check the voltage at the sensor between socket A and socket B. Repeat this step for all of the analog sensors that are connected to the ECM.
- Turn the keyswitch to the OFF position.
Expected Result:
The supply voltage is 5.0 ± 0.2 VDC after each analog sensor is connected.
Results:
- OK - The supply voltage is 5.0 ± 0.2 VDC after each analog sensor is connected. The analog supply voltage is correct when all of the sensors are connected. The analog sensor supply and the harness are okay.
Repair: If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".
Stop.
- Not OK - The supply voltage is not 5.0 ± 0.2 VDC after a sensor is connected. The voltage is okay before the sensor is connected. The voltage is not okay after the sensor is connected. The sensor may be internally shorted.
Repair: Temporarily replace the sensor. Verify that the new sensor solves the problem before permanently installing the new sensor.
Stop.