C27 Generator Set Engines Caterpillar

Sensor Signal (Analog, Passive) - Test

Usage:

C27 N1B

System Operation Description:

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

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Table 1
Diagnostic Trouble Codes
J1939 Code and Description	Conditions that Generate the Code	System Response
105-3 Engine Intake Manifold #1 Temperature : Voltage Above Normal	The Electronic Control Module (ECM) detects the following conditions: The signal voltage from the intake manifold air temperature sensor is greater than 4.95 VDC for more than 8 seconds.	The code is logged. Engine coolant temperature is above −10 °C (15.0 °F). The ECM will use the default value of 70 °C (158 °F). The engine may show the following symptoms: Poor stability Poor cold running White smoke
105-4 Engine Intake Manifold #1 Temperature : Voltage Below Normal	The ECM detects the following conditions: The signal voltage from the intake manifold air temperature sensor is less than 0.2 VDC for more than 8 seconds.
110-3 Engine Coolant Temperature : Voltage Above Normal	The ECM detects signal voltage that is greater than 4.95 VDC for 8 seconds.	The code is logged. The code is logged after seven minutes. The value of the parameter is set to 90 °C (194 °F).
110-4 Engine Coolant Temperature : Voltage Below Normal	The ECM detects signal voltage that is less than 0.2 VDC for 8 seconds.
172-3 Engine Air Inlet Temperature : Voltage Above Normal	The ECM detects signal voltage that is greater than 4.95 VDC for 8 seconds.	The code is logged. Ambient temperature must be greater than −35 °C (−31 °F) in order to allow logging of this diagnostic code. The value of the parameter is set to 85 °C (185 °F).
172-4 Engine Air Inlet Temperature : Voltage Below Normal	The ECM detects signal voltage that is less than 0.2 VDC for 8 seconds.	The code is logged. Ambient temperature must be less than 140 °C (284 °F) in order to allow logging of this diagnostic code. The value of the parameter is set to 85 °C (185 °F).
174-3 Engine Fuel Temperature 1 : Voltage Above Normal	The ECM detects signal voltage that is greater than 4.95 VDC for 8 seconds.	The code is logged. Engine coolant temperature must be above −10 °C (14 °F) in order to allow logging of this diagnostic code. The value of the parameter is set to the value of the engine coolant temperature.
174-4 Engine Fuel Temperature 1 : Voltage Below Normal	The ECM detects signal voltage that is less than 0.2 VDC for 8 seconds.	The code is logged. The value of the parameter is set to the value of the engine coolant temperature.
175-3 Engine Oil Temperature 1 : Voltage Above Normal	The ECM detects signal voltage that is greater than 4.95 VDC for 8 seconds.	The code is logged.
175-4 Engine Oil Temperature 1 : Voltage Below Normal	The ECM detects signal voltage that is less than 0.2 VDC for 8 seconds.	The code is logged.
412-3 Engine Exhaust Gas Recirculation Temperature : Voltage Above Normal	The ECM detects signal voltage that is greater than 4.95 VDC for 8 seconds.	The code is logged.
412-4 Engine Exhaust Gas Recirculation Temperature : Voltage Below Normal	The ECM detects signal voltage that is less than 0.2 VDC for 8 seconds.	The code is logged.
1131-3 Engine Intake Manifold #2 Temperature : Voltage Above Normal	The ECM detects signal voltage that is greater than 4.95 VDC for 8 seconds.	The code is logged. The code will not be logged if the ambient temperature is below −30° C (−22° F). The code may be active or the logged code may be pending until this temperature is reached. The value of the parameter is set to the value of the other intake manifold temperature sensor. If both sensor signals are lost, a value of 85° C (185° F)will be used.
1131-4 Engine Intake Manifold #2 Temperature : Voltage Below Normal	The ECM detects signal voltage that is less than 0.2 VDC for 8 seconds.	The code is logged. Ambient air temperature must be less than 140° C (284° F) in order to allow logging of this diagnostic code. The code may be active or the logged code may be pending until this temperature is reached. The value of the parameter is set to the value of the other intake manifold temperature sensor. If both sensor signals are lost, a value of 85° C (185° F) will be used.

System Overview

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

Diagnostics on the Caterpillar Electronic Technician (ET)

Wiggle Test - The Wiggle Test allows you to monitor the status of the signals from the sensors.

For additional information regarding the Wiggle Test, refer to the documentation that accompanies the Cat ET software.

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Illustration 1	g02175198
Schematic for the passive sensors

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Illustration 2	g02175299
Terminal locations at the P1 ECM connector for the passive sensors (P1-3) Return (P1-5) Return (P1-16) Engine oil temperature (P1-17) Air inlet temperature

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Illustration 3	g02134161
Terminal locations at the P2 ECM connector for the passive sensors (P2-17) Return (P2-30) Return (P2-56) Intake manifold air temperature (right side) (P2-62) NRS temperature (P2-83) Return (P2-84) Engine coolant temperature (P2-95) Intake manifold air temperature (left side) (P2-96) Fuel temperature

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Illustration 4	g01155187
Terminal locations at the connector for the passive analog sensors (Terminal 1) Sensor signal (Terminal 2) Sensor return

Test Step 1. Check for Diagnostic Codes

Connect Cat ET to the service tool connector.
Restore electrical power to the ECM.
Start the engine.
Access the "Active Diagnostic Code" screen on Cat ET.
Note: The engine must be running for seven minutes in order for a 110-3 code to become active.
Look for these active codes or logged codes:
- -3
- -4

Results:

Logged Code - A diagnostic code is logged. Proceed to Test Step 4.
Active -3 - A -3 diagnostic code is active. Proceed to Test Step 2.
Active -4 - A -4 diagnostic code is active. Proceed to Test Step 3.

Test Step 2. Create a Short at the Sensor Connector

Remove electrical power to the ECM.
Disconnect the suspect sensor.
Install the jumper wire between terminal 1 (sensor signal) and terminal 2 (sensor return) at the sensor connector.
Restore electrical power to the ECM.
Monitor the diagnostic codes on Cat ET. Check for an active -4 diagnostic code for the suspect sensor.
Note: The engine must be running for seven minutes in order for a 110-3 code to become active.
Remove electrical power to the ECM.

Results:

Active -3 - The -3 diagnostic code remains active for the suspect sensor.
Repair: There is an open in the harness. Repair the wiring or replace the harness.
Verify that the problem is resolved.

STOP
Active -4 - A -4 diagnostic code became active after creating the short at the sensor connector.
Repair: The wiring is OK. Replace the sensor.
Verify that the problem is resolved.

STOP

Test Step 3. Create an Open at the Suspect Sensor Connector

Remove electrical power to the ECM.
Disconnect the sensor connector of the suspect sensor with the active -4 diagnostic code.
Restore electrical power to the ECM.
Monitor the diagnostic codes on Cat ET. Check for an active -3 diagnostic code for the suspect sensor.
Note: The engine must be running for seven minutes in order for a 110-3 code to become active.
Remove electrical power to the ECM.

Results:

Active -4 - The -4 diagnostic code remains active for the suspect sensor.
Repair: There is a short in the harness. Repair the wiring or replace the harness.
Verify that the problem is resolved.

STOP
Active -3 - A -3 diagnostic code became active after disconnecting the sensor.
Repair: The wiring is OK. Replace the sensor.
Verify that the problem is resolved.

STOP

Test Step 4. Perform the Wiggle Test

Carefully following this procedure is the best way to identify the root cause of an intermittent problem.

Restore electrical power to the ECM.
Use Cat ET to run the "Wiggle Test".
Slowly wiggle the wiring and the connectors between the P2 connector and the sensor. Slowly wiggle the wiring and the connectors between the P1 connector and the sensor. Pay particular attention to the wiring near each connector. Be sure to wiggle all of the wiring.
As you wiggle the wiring look for the following problems:
- Loose connectors or damaged connectors
- Moisture on the connectors or the wiring
- Damage that is caused by excessive heat
- Damage that is caused by chafing
- Improper routing of wiring
- Damaged insulation

Results:

The wiring failed the wiggle test. -
Repair: There is a problem with the wiring. Repair the wiring or replace the wiring.
Verify that the problem is resolved.

STOP
The wiring passed the Wiggle Test. -
Repair: The problem may be intermittent. Inspect the wiring. Refer to Troubleshooting, "Electrical Connectors - Inspect".
If the wiring is OK, perform the following procedure:
1. Remove electrical power to the ECM.
1. Disconnect the connectors. Carefully inspect the terminals for proper installation. Ensure that each terminal is clean and dry.
2. Insert a pin into each socket. Verify that each socket grips the pin firmly. Repair any problems.
3. Connect all connectors.
4. Verify that the problem is resolved.
5. Return the unit to service.
STOP