C7.1 Engines and Generator Sets Caterpillar

Sensor Supply - Test

Usage:

C7.1 770

This procedure covers the following diagnostic codes:

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Table 1
Diagnostic Trouble Codes for Sensor Supplies
J1939 Code	CDL Code	Code Description (code descriptions may vary)	Comments
678-3	41-3	ECU 8 Volts DC Supply : Voltage Above Normal	The ECM detects the following conditions: The 8 VDC supply is more than 8.8 VDC for more than one second. The ECM has been powered for more than 3 seconds. Diagnostic code 168-4 is not active. The ECM will log the diagnostic code and the warning lamp will illuminate while this diagnostic code is active. The engine may be limited to low idle.
678-4	41-4	ECU 8 Volts DC Supply : Voltage Below Normal	The ECM detects the following conditions: The 8 VDC supply is less than 7.2 VDC for more than one second. The ECM has been powered for more than 3 seconds. Diagnostic code 168-4 is not active. The ECM will log the diagnostic code and the warning lamp will illuminate while this diagnostic code is active. The engine may be limited to low idle. An active diagnostic code may not cause any noticeable effect on engine response unless the voltage drops below 6.5 VDC.
3509-3	262-3	Sensor Supply Voltage 1 : Voltage Above Normal	The Electronic Control Module (ECM) detects the following conditions: The 5 VDC supply for the sensors is greater than 5.16 VDC for more than one second. The ECM has been powered for at least 3 seconds. Diagnostic code 168-4 is not active. The warning lamp will come on. The ECM sets all the sensors on the 5 VDC circuit to the default values. The engine will be derated.
3510-3	2131-3	Sensor Supply Voltage 2 : Voltage Above Normal
3509-4	262-4	Sensor Supply Voltage 1 : Voltage Below Normal	The ECM detects the following conditions: The 5 VDC supply for the sensors is less than 4.84 VDC for more than one second. The ECM has been powered for at least 3 seconds. Diagnostic code 168-4 is not active. The warning lamp will come on. The ECM sets all the sensors on the 5 VDC circuit to the default values. The engine will be derated.
3510-4	2131-4	Sensor Supply Voltage 2 : Voltage Below Normal
100-21	100-21	Engine Oil Pressure : Data Drifted Low	The ECM detects no 5 VDC supply to the engine oil pressure sensor.
108-21	274-21	Barometric Pressure : Data Drifted Low	The ECM detects no 5 VDC supply to the barometric pressure sensor.
3358-21	3385-21	Engine Exhaust Gas Recirculation Inlet Pressure : Data Drifted Low	The ECM detects no 5 VDC supply to the Nox Reduction System (NRS) inlet pressure sensor.
3563-21	1785-21	Engine Intake Manifold #1 Absolute Pressure : Data Drifted Low	The ECM detects no 5 VDC supply to the intake manifold pressure sensor.
3609-21	3464-21	Diesel Particulate Filter Intake Pressure 1 : Data Drifted Low	The ECM detects no 5 VDC supply to the Diesel Particulate Filter (DPF) inlet pressure sensor.
3837-21	3493-21	Aftertreatment 1 Secondary Air Pressure : Data Drifted Low	The ECM detects no 5 VDC supply to the Aftertreatment Regeneration Device (ARD) air pressure sensor.

Note: A 678-XX or 41-XX diagnostic code indicates a fault in the 8 VDC circuit on the J1/P1 connector. A 3509-XX or 262-XX diagnostic code indicates a fault in the 5 VDC circuit on the J2/P2 connector. A 3510-XX or 2131-XX diagnostic code indicates a fault in the 5 VDC circuit on the J1/P1 connector.

The following background information is related to this procedure:

The ECM supplies regulated +5 VDC to the following sensors on P2:46:

The position sensor for the intake throttle valve
The position sensor for the NRS Valve
Engine oil pressure sensor

The ECM supplies regulated +5 VDC to the following sensors on P2:47:

The NRS inlet pressure sensor
The NRS differential pressure sensor
Fuel rail pressure sensor
Barometric pressure sensor
Intake manifold pressure sensor

The ECM supplies regulated +5 VDC to the following components on P2:45:

The position sensor for the combustion air valve
ARD pilot fuel pressure sensor
ARD air pressure sensor
The DPF inlet pressure sensor
The DPF differential pressure sensor
The inlet temperature sensor for the DPF and the ARD flame detection temperature sensor
The aftertreatment identification module

The ECM supplies regulated +5 VDC to the analog throttle position sensors (if equipped) on P1:2.

The ECM supplies regulated +8 VDC to the speed/timing sensors on P2:44 and to the digital throttle on P1:4.

A diagnostic code can be caused by the following conditions:

An open circuit in the harness
A short circuit in the harness
A short circuit to a voltage that is higher than 5.16 VDC
A faulty sensor
A faulty ECM

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Illustration 1	g06154952
Schematic for the 5 VDC supply on P1:2 (if equipped)

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Illustration 2	g06154865
Schematic for the 5 VDC supply on P2:46 and P2:47

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Illustration 3	g06154896
Schematic for the 5 VDC supply on P2:45

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Illustration 4	g06155027
Schematic for the 8 VDC supply on P1:4

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Illustration 5	g06155228
P1 pin locations for the sensor supply (2) 5 VDC supply (3) Ground (4) 8 VDC supply (5) Ground

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Illustration 6	g06155239
P2 pin locations for the sensor supply (44) 8 VDC supply (45) 5 VDC supply for the CEM (46) 5 VDC supply #1 (47) 5 VDC supply #2 (55) CEM ground (56) Ground #1 (57) Ground #2

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Illustration 7	g02315513
Typical example of the fuel rail pressure sensor (1) Sensor ground (3) 5 VDC supply

Note: The position of the terminal for the voltage supply on the fuel rail pressure sensor is different to all other engine pressure sensors.

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Illustration 8	g02315514
Typical example of an engine pressure sensor (1) 5 VDC supply (2) Sensor ground

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Illustration 9	g02315533
Typical example of the connector for the intake throttle valve (1) 5 VDC supply (3) Sensor ground

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Illustration 10	g02315534
Typical example of the connector for the NRS valve (1) 5 VDC supply (2) Sensor ground

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Illustration 11	g02315535
Typical example of the connector for the combustion air valve (1) 5 VDC supply (2) Sensor ground

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Illustration 12	g02315536
Typical example of the connector for the inlet temperature sensor for the DPF and the ARD flame detection temperature sensor (1) 5 VDC supply (2) Sensor ground

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Illustration 13	g02315537
Typical example of the connector for the aftertreatment identification module (1) 5 VDC supply (6) Ground

Complete the procedure in the order in which the steps are listed.

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Table 2
Troubleshooting Test Steps	Values	Results
1. Check for Connector Damage A. Turn the keyswitch to the OFF position. B. Check the connectors and the harness for the following faults: · Damage · Abrasion · Corrosion · Incorrect attachment C. Refer to Troubleshooting, "Electrical Connectors - Inspect". D. Perform a 45 N (10 lb) pull test on each of the wires in the harness that are associated with the throttle position sensors. Check the wire connectors for all the sensors on the sensor supply circuits. E. Check the screws for the ECM connectors for the correct torque of 6 N·m (53 lb in).	Connector fault	Result: Found damage, abrasion, corrosion, or incorrect attachment. Repair: Repair the connectors or the harness and/or replace the connectors or the harness. Use the electronic service tool to clear all logged diagnostic codes and then verify that the repair eliminates the fault. Result: No faults found. Proceed to Test Step 2.
2. Check for Active Diagnostic Codes A. Connect the electronic service tool to the diagnostic connector. B. Turn the keyswitch to the ON position. C. Use the electronic service tool to monitor the diagnostic codes. Wait at least 15 seconds in order for the diagnostic codes to become active. Check and record any active diagnostic codes.	Diagnostic codes	Result: One or more of the diagnostic codes listed in Table 1 is active or recently logged. Proceed to Test Step 3. Result: None of the previous diagnostic codes are active. The fault may be intermittent. Proceed to Test Step 7.
3. Disconnect the Sensors One at a Time A. Turn the keyswitch to the OFF position. B. For a 3509-X (262-X) diagnostic code, disconnect the sensors on the 5 VDC supply circuit on the J2/P2 connector one at a time. Refer to Illustration 2. Wait for 30 seconds after each sensor is disconnected. Use the electronic service tool to monitor the diagnostic codes. For a 3510-X (2131-X) diagnostic code, disconnect the analog throttle position sensors (if equipped) one at a time. Also, disconnect the aftertreatment ID module and any other sensors that are connected to the 5 VDC supply on the P1 connector. Refer to Illustration 1. Wait for 30 seconds after each sensor is disconnected. Use the electronic service tool to monitor the diagnostic codes. For a 678-X (41-X) diagnostic code, disconnect the digital throttle position sensors (if equipped) one at a time. Also, disconnect any other sensors that are connected to the 8 VDC supply on the P1 connector. Refer to Illustration 3. Wait for 30 seconds after each sensor is disconnected. Use the electronic service tool to monitor the diagnostic codes. Note: The sensor supply diagnostic will become inactive when the sensor that caused the diagnostic code is disconnected. C. Ensure that all the sensors on the suspect sensor supply circuit are disconnected.	Diagnostic code inactive	Result: The 3509 (262) or 3510 (2131) diagnostic code is inactive when all the sensors are disconnected. Repair: Replace the suspect sensor. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: A 3509 (262) diagnostic code is still active. Proceed to Test Step 4. Result: A 3510, (2131) or 678 (41) diagnostic code is still active. Proceed to Test Step 5.
4. Disconnect the ECM Connector A. Turn the keyswitch to the OFF position. B. Disconnect the P2 connector from the ECM. Thoroughly inspect the P2/J2 connectors for corrosion and/or damaged seals. Repair if necessary. C. Turn the keyswitch to the ON position. D. Use the electronic service tool to check for active diagnostic codes. Note: With the P2 connector disconnected, diagnostic codes will be active for all the engine sensors. Disregard all other codes and look for a 3509-X (262-X) diagnostic code only. E. Turn the keyswitch to the OFF position.	Diagnostic code inactive	Result: The 3509 (262) diagnostic code is no longer active. Repair: Replace the engine wiring harness. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The 3509 (262) diagnostic code is still active with the P2 connector disconnected. Contact the Dealer Solutions Network (DSN).
5. Check the Wiring for an Open Circuit or High Resistance A. Disconnect any sensors that are connected to the suspect sensor supply circuit. Disconnect the P1 connector from the ECM. Thoroughly inspect the P1/J1 connectors for corrosion and/or damaged seals. Repair if necessary. B. Measure the resistance of the following wires for each sensor: · The sensor supply wire from the sensor to the P1 connector · The sensor ground wire from the sensor to the P1 connector	Less than 2.0 Ohms	Result: At least one of the resistance measurements is greater than 2.0 Ohms. Repair: Replace the wiring with the high resistance. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Each resistance measurement is less than 2.0 Ohms. Proceed to Test Step 6.
6. Check the Wiring for a Short Circuit A. Measure the following resistances: · P1:2 and all other terminals on the P1 connector · P1:4 and all other terminals on the P1 connector · P1:44 and all other terminals on the P1 connector	Greater than 100 Ohms	Result: At least one of the resistance measurements is less than 100 Ohms. Repair: Replace the wiring between the sensor and the P1 connector. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: All resistance measurements are greater than 100 Ohms. Contact the Dealer Solutions Network (DSN).
7. Perform the "Wiggle Test" on the Electronic Service Tool A. Select the "Wiggle Test" from the diagnostic tests on the electronic service tool. B. Choose the appropriate group of parameters to monitor. C. Press the "Start" button. Wiggle the wiring harness to reproduce intermittent faults. If an intermittent fault exists, the status will be highlighted and an audible beep will be heard.	No faults	Result: No intermittent faults were found. The harness and connectors appear to be OK. Return the engine to service. Result: At least one intermittent fault was indicated. Repair: Repair or replace the harness or connector. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.