C9.3 Engines for Caterpillar Built Machines Sensor Supply

Sensor Supply - Test

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System Operation Description:

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

Note: Some of the following codes may not be applicable for certain applications.

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Table 1
Diagnostic Codes Table
CDL Code	Code Description	Comments
41-3	8 VDC Supply : Voltage Above Normal	The code is logged.
41-4	8 VDC Supply : Voltage Below Normal	The code is logged.
262-3	5 Volt Sensor DC Power Supply : Voltage Above Normal	The code is logged. All sensors are set to default values.
262-4	5 Volt Sensor DC Power Supply : Voltage Below Normal	The code is logged. All sensors are set to default values.
274-21	Atmospheric Pressure Sensor : Data Drifted Low	The code is logged. The 5 VDC supply to the sensor has been lost.
460-21	Fuel Pressure Sensor - After Fuel Filter : Data Drifted Low	The code is logged. The 5 VDC supply to the sensor has been lost.
1785-21	Intake Manifold Pressure Sensor : Data Drifted Low	The code is logged. The 5 VDC supply to the sensor has been lost.
2131-3	5 v Sensor DC Power Supply #2 : Voltage Above Normal	The code is logged. Engine power may be derated.
2131-4	5 v Sensor DC Power Supply #2 : Voltage Below Normal	The code is logged. Engine power may be derated.

System Operation

The Electronic Control Module (ECM) supplies a regulated voltage of 5.0 ± 0.2 VDC to the following sensors:

Engine oil pressure sensor
Barometric pressure sensor
Crankcase pressure sensor
Intake manifold pressure sensor
Fuel pressure sensor after the filter
Air inlet pressure sensor

The supply voltage for the sensors is routed from the ECM to terminal 1 of each sensor connector. The sensor return for the sensors is routed from the ECM to terminal 2 of each sensor connector. The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.

Note: The sensors are not protected from overvoltage. A short from the supply line to the +Battery may damage the sensors. If any of the diagnostic codes are active, a sensor may have been damaged. Repair the sensor supply and check for any active sensor diagnostic codes in order to determine if a sensor has been damaged.

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Illustration 1	g02177069
Typical schematic

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Illustration 2	g02452983
Terminal locations at the P2 ECM connector for the passive analog sensors (P2-72) +5 Sensor Power Supply (Left side of the engine) (P2-81) +5 Sensor Power Supply (Right side of the engine) (P2-83) Engine Return (right side) (P2-93) Engine Return (left side)

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Illustration 3	g02101833
Terminal locations at the P1 ECM connector for the passive analog sensors (P1-4) +8 Sensor Power Supply

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Illustration 4	g01240891
Sensor connector (A) 5 V or 8 V sensor supply (B) Sensor return (C) Signal

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Table 2
Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Connect Cat ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools", if necessary. B. Determine if a diagnostic trouble code is present.	Codes	Result: A -3 or -4 code is present. Repair: Inspect the wiring at each sensor. Look for broken wiring or problems with a connector. Make the necessary repairs. STOP Result: A -21 code is present. There is an intermittent loss or solid loss of 5 v supply to the sensor. Proceed to Test Step 2.
2. Check the Sensor Supply A. Turn the keyswitch to the ON position. Do not start the engine. B. Perform the "Wiggle Test" in Cat ET. C. Unplug the suspect sensor. D. Place a jumper wire across pin 1 to pin 2.	Sensor	Result: A 41-4, a 2131-4 or a 262-4 code is activated. Repair: There is a problem with the sensor. Replace the sensor. STOP Result: A 41-4, a 2131-4 or a 262-4 code is not activated. Repair: The problem is in the wiring from the ECM to the sensor. Repair the wiring or replace the wiring. STOP

Test Step 1.

The procedure corrected the issue. Return to service.

Results:

The procedure did not correct the issue. -
Repair: Contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).

STOP