G3306B Petroleum Generator Set Engines Caterpillar

Sensor Signal (Analog, Passive) - Test

Usage:

Use this procedure to troubleshoot the electrical system if a problem is suspected with an engine temperature sensor. Also, use this procedure if any one of the diagnostic codes in Table 1 is active or easily repeated.

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Table 1
Diagnostic Codes Table
Code and Description	Conditions which Generate this Code	System Response
105-3 Engine Intake Manifold #1 Temperature : Voltage Above Normal	The Electronic Control Module (ECM) detects a signal voltage that is more than 4.95 VDC for ten seconds.	The code is logged. The amber warning lamp is illuminated. The service tool displays "Error Indicator" on the status screen for this parameter.
105-4 Engine Intake Manifold #1 Temperature : Voltage Below Normal	The ECM detects a signal voltage that is less than 0.2 VDC for eight seconds.
110-3 Engine Coolant Temperature : Voltage Above Normal	The ECM detects a signal voltage that is more than 4.95 VDC for ten seconds.	The code is logged. The amber warning lamp is illuminated. The service tool displays "Error Indicator" on the status screen for this parameter.
110-4 Engine Coolant Temperature : Voltage Below Normal	The ECM detects a signal voltage that is less than 0.2 VDC for eight seconds.
175-3 Engine Oil Temperature 1 : Voltage Above Normal	The ECM detects a signal voltage that is more than 4.95 VDC for ten seconds.	The code is logged. The amber warning lamp is illuminated. The service tool displays "Error Indicator" on the status screen for this parameter.
175-4 Engine Oil Temperature 1 : Voltage Below Normal	The ECM detects a signal voltage that is less than 0.2 VDC for eight seconds.

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Illustration 1	g01961988
Schematic for the passive analog sensor

System Operation

Use this procedure to troubleshoot any suspect problems with the temperature sensors for the engine.

The sensor signal for the passive sensor is routed from the ECM to terminal 1 of the sensor connector. The sensor return for the passive sensors is routed from the ECM to terminal 2 of the sensor connector.

The most likely cause of a code is a problem with an electrical connector or wiring. The least likely cause of a code is the ECM.

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Illustration 2	g01962016
Locations of the passive analog sensor (left side engine view) (1) Engine coolant temperature sensor (2) Intake manifold air temperature sensor (3) Engine oil temperature sensor

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Illustration 3	g01962019
Locations of the connectors at the ECM (right front engine view) (4) J2/P2 ECM connectors

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Illustration 4	g01962021
Terminal locations at the P2 ECM connector for the passive analog sensors (P2-36) Engine oil temperature (P2-39) Analog return (P2-42) Intake manifold air temperature (P2-43) Engine coolant temperature

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Illustration 5	g01436505
Terminal locations at the connector for the passive analog sensor (Terminal 1) Sensor signal (Terminal 2) Analog sensor return

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Table 2
Troubleshooting Test Steps	Values	Results
1. Check for Active Diagnostic Codes and Check for Logged Diagnostic Codes A. Connect Caterpillar Electronic Technician (ET) to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools", if necessary. B. Download the "Product Status Report" from the engine ECM before performing any troubleshooting or clearing diagnostic trouble codes. C. Monitor the active diagnostic code screen on Cat ET. Record any active diagnostic codes. Note. Wait at least 30 seconds in order for diagnostic codes to become active.	Logged Diagnostic Codes Or Active Diagnostic Codes	Results: A diagnostic code is logged but is not active. Repair: Do not troubleshoot a logged code unless the code relates to an operator complaint. If the code is logged and the code does not relate to an operator complaint, clear the code. If the logged code relates to this procedure, inspect the electrical connectors and the wiring for the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" Results: A -3 diagnostic code is active. Proceed to Test Step 2. Results: A -4 diagnostic code is active. Proceed to Test Step 6.
2. Inspect the Electrical Connectors and the Wiring A. Check the harness and the wiring for abrasion and for pinch points. B. Thoroughly inspect all connectors that are in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect " for details.	-3 code	Results: The connectors and wiring are OK. Proceed to Test Step 3. Results: The connectors and/or wiring are NOT OK. Repair: Repair the connectors or wiring and/or replace the connectors or wiring.
3. Check for Battery Voltage on the Signal Wire A. At the sensor harness connector, measure the voltage between the signal terminal and the return terminal. B. Record the result.	-3 code (+) Battery voltage	Results: The voltage is OK. The voltage measurement is less than the +Battery voltage. The signal wire is not shorted to the +Battery. Proceed to Test Step 4. Note: The following Results: will cause a -3 code. Results: The voltage is NOT OK. The voltage measurement is approximately the +Battery voltage. The signal wire is shorted to the +Battery. Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.
4. Determine if the Sensor has an Open Circuit Condition by Creating a Short Circuit at the Sensor Connector A. Using appropriate terminals, fabricate a jumper wire. B. At the sensor harness connector, connect the signal terminal and the return terminal with the jumper wire. The jumper will replace the sensor with a short circuit. Note. Wait at least 30 seconds in order for the diagnostic codes to become active. C. Record the resulting diagnostic code.	-3 Code	Results: A -3 diagnostic code is active when the connector is disconnected. A -4 diagnostic code is active when the jumper wire is shorting the circuit. The sensor is NOT OK. The open is in the sensor. Repair: Perform the following procedure: 1. Temporarily connect a new sensor. 2. Recheck the circuit in order to ensure that the original problem is resolved with the connection of the new the sensor. 3. If the problem is resolved with the new sensor, reconnect the suspect sensor. If the problem returns with the connection of the suspect sensor, permanently install the new sensor. 4. Before returning the engine to service, clear the logged diagnostic codes. Results: The -3 diagnostic code remains active when the jumper wire is shorting the circuit. The sensor is OK. The open is in the remainder of the circuit. Proceed to Test Step 5.
5. Check the Operation of the ECM by Creating a Short Circuit at the ECM Connector A. At the ECM harness connector, remove the signal wire and the return wire. B. Using appropriate terminals, fabricate a jumper wire. C. At the ECM harness connector, install the jumper wire between the signal terminal location and the return terminal location. The jumper will replace the engine wiring with a short circuit. Note. Wait at least 30 seconds in order for the diagnostic codes to become active. D. Record the resulting diagnostic code.	-3 code	Results: A -3 diagnostic code is active when the wires are removed. A -4 diagnostic code is active when the jumper wire is shorting the circuit. The ECM is OK. There is an open in the wiring that is between the ECM and the sensor. Repair: Perform the following procedure: 1. Repair the connectors or wiring and/or replace the connectors or wiring. 2. Recheck the circuit in order to ensure that the original problem is resolved. 3. Before returning the engine to service, clear the logged diagnostic codes. Results: The -3 diagnostic code remains active when the jumper wire is shorting the circuit. The ECM appears to be NOT OK . Note: Before you consider replacing the ECM, consult with your Cat dealers Technical Communicator (TC) for assistance. Repair: Perform the following procedure: 1. Temporarily connect a test ECM. Refer to Troubleshooting, "ECM - Replace". 2. Recheck the circuit in order to ensure that the original problem is resolved. If the problem is resolved with the test ECM, reconnect the suspect ECM. If the problem returns with the suspect ECM, permanently install the new ECM. Verify that the problem is resolved. If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring. 3. Before returning the engine to service, clear the logged diagnostic codes.
6. Inspect the Electrical Connectors and the Wiring A. Check the harness and the wiring for abrasion and for pinch points. B. Thoroughly inspect all connectors that are in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect " for details.	-4 code	Results: The connectors and wiring are OK. Proceed to Test Step 7. Results: The connectors and/or wiring are Not OK. Repair: Repair the connectors or wiring and/or replace the connectors or wiring.
7. Determine if the Sensor has a Short Circuit Condition by Creating an Open Circuit at the Sensor Connector A. Disconnect the harness connector from the sensor that relates to the code. Note. Wait at least 30 seconds in order for the diagnostic codes to become active. C. Record the resulting diagnostic code.	-4 code	Results: A -4 diagnostic code is active when the connector is connected. A -3 diagnostic code is active when the connector is disconnected. The sensor is NOT OK. The short is in the sensor. Repair: Perform the following procedure: 1. Temporarily connect a new sensor. 2. Recheck the circuit in order to ensure that the original problem is resolved with the connection of the new the sensor. 3. If the problem is resolved with the new sensor, reconnect the suspect sensor. If the problem returns with the connection of the suspect sensor, permanently install the new sensor. 4. Before returning the engine to service, clear the logged diagnostic codes. Results: The -4 diagnostic code remains active when the connector is disconnected. The sensor is OK. The open is in the remainder of the circuit. Proceed to Test Step 8.

8. Check the Operation of the ECM by Creating an Open Circuit at the ECM Connector A. At the ECM harness connector, remove the signal wire. Note. Wait at least 30 seconds in order for the diagnostic codes to become active. C. Record the resulting diagnostic code.	-4 code	Results: A -4 diagnostic code is active when the wire is connected. A -3 diagnostic code is active when the wire is removed. The ECM is OK. There is an open in the wiring that is between the ECM and the sensor. Repair: Perform the following procedure: 1. Repair the connectors or wiring and/or replace the connectors or wiring. 2. Recheck the circuit in order to ensure that the original problem is resolved. 3. Before returning the engine to service, clear the logged diagnostic codes. Results: The -4 diagnostic code remains active after the wire is removed. The ECM appears to be NOT OK . Note: Before you consider replacing the ECM, consult with your Cat dealers Technical Communicator (TC) for assistance. Repair: Perform the following procedure: 1. Temporarily connect a test ECM. Refer to Troubleshooting, "ECM - Replace". 2. Recheck the circuit in order to ensure that the original problem is resolved. If the problem is resolved with the test ECM, reconnect the suspect ECM. If the problem returns with the suspect ECM, permanently install the new ECM. Verify that the problem is resolved. If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring. 3. Before returning the engine to service, clear the logged diagnostic codes.