C7.1 Engines and Generator Sets Caterpillar

Valve Position - Test

Usage:

C7.1 770

This procedure covers the following diagnostic codes:

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Table 1
Diagnostic Codes for the Valve Position Sensors
J1939 Code	CDL Code	Code Description (code descriptions may vary)	Comments
27-3	3407-3	EGR #1 Valve Position : Voltage Above Normal	The Electronic Control Module (ECM) detects the following conditions: The signal voltage from the position sensor on the NOx Reduction System (NRS) valve is greater than 4.8 VDC for 0.1 seconds. The warning lamp will come on. The ECM will log the diagnostic code. The NRS valve will be fully closed while the code is active. The engine will be derated.
27-4	3407-4	EGR #1 Valve Position : Voltage Below Normal	The ECM detects the following conditions: The signal voltage from the NRS valve position sensor is less than 0.2 VDC for 0.1 seconds. The warning lamp will come on. The ECM will log the diagnostic code. The NRS valve will be fully closed while the code is active. The engine will be derated.
51-3	3515-3	Engine Throttle Position : Voltage Above Normal	The ECM detects the following conditions: The signal voltage from the position sensor on the engine intake throttle valve is greater than 4.8 VDC for 0.1 seconds. If equipped, the warning lamp will come on. The ECM will log the diagnostic code. The engine intake throttle valve will be fully closed while the code is active. The engine will be derated.
51-4	3515-4	Engine Throttle Position : Voltage Below Normal	The ECM detects the following conditions: The signal voltage from the position sensor on the engine intake throttle valve is less than 0.2 VDC for 0.1 seconds. If equipped, the warning lamp will come on. The ECM will log the diagnostic code. The engine intake throttle valve will be fully closed while the code is active. The engine will be derated.
3488-3	2490-3	Aftertreatment #1 Air Pressure Actuator Position : Voltage Above Normal	The ECM detects the following conditions: The signal voltage from the position sensor on the combustion air valve is greater than 4.85 VDC for 8 seconds. If equipped, the warning lamp will come on. The ECM will log the diagnostic code. The engine will be derated.
3488-4	2490-4	Aftertreatment #1 Air Pressure Actuator Position : Voltage Below Normal	The ECM detects the following conditions: The signal voltage from the position sensor on the combustion air valve is less than 0.2 VDC for 8 seconds. If equipped, the warning lamp will come on. The ECM will log the diagnostic code. The engine will be derated.

The following conditions must exist before any of the preceding codes will become active:

The ECM has been powered for at least 2 seconds.
There are no active 168 codes.
There are no active 3509 (262) codes.

Use this procedure to troubleshoot the position sensors for the following valves:

NRS valve
Engine intake throttle valve
Combustion air valve for the Aftertreatment Regeneration Device (ARD)

Each position sensor is integral in the associated valve. If the following procedure indicates a fault with the position sensor, then the entire valve must be replaced.

The following background information is related to this procedure:

The troubleshooting procedures for the diagnostic codes of each position sensor are identical. The 5 VDC sensor supply provides power to all 5 VDC sensors. The ECM supplies 5.0 VDC to terminal "5" of the engine intake throttle valve connector and to terminal "1" of the other valve connectors. The sensor common from the ECM connector goes to terminal "3" of the engine intake throttle valve connector. The sensor common from the ECM connector goes to terminal "2" of the other valve connectors. The sensor supply is output short circuit protected. A short circuit to the battery will not damage the circuit inside the ECM. The signal voltage from terminal "4" of the engine intake throttle valve is supplied to the appropriate terminal at the P2 ECM connector. The signal voltage from terminal "3" of the other valves is supplied to the appropriate terminal at the P2 ECM connector.

Pull-up Voltage

The ECM continuously outputs a pull-up voltage on the circuit for the sensor signal wire. The ECM uses this pull-up voltage to detect an open in the signal circuit. When the ECM detects a voltage above a threshold on the signal circuit, the ECM generates an open circuit diagnostic code (XXXX-3) for the sensor.

If the sensor is disconnected, pull-up voltage at the sensor connector indicates that the wires are not open or shorted to ground. If the sensor is disconnected , the absence of pull-up voltage indicates an open in the signal wire or a short to ground. If the sensor is disconnected and the voltage is different from pull-up voltage, the signal wire is shorted to another wire in the harness.

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Illustration 1	g06156781
Schematic diagram for the valve position sensors

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Illustration 2	g01981373
Typical view of the pin locations on the P2 connector for the position sensors (3) Engine intake throttle valve position sensor signal (15) NRS valve position sensor signal (16) Combustion air valve position sensor signal (45) Combustion air valve position sensor 5 VDC supply (46) Engine intake throttle valve, NRS valve position sensors 5 VDC supply (55) Combustion air valve position sensor ground (56) Engine intake throttle valve, NRS valve position sensors ground

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Illustration 3	g02186473
Typical view of the pin locations for the valve position sensors on the connectors from the engine to the Clean Emissions Module (CEM) (1) 5 VDC supply (2) Combustion air valve position sensor ground (9) Combustion air valve position sensor signal

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Illustration 4	g03177615
Connector for the NRS valve (1) 5 VDC supply (2) Position sensor ground (3) Position sensor signal

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Illustration 5	g03177636
Connector for the combustion air valve (1) 5 VDC supply (2) Position sensor ground (3) Position sensor signal

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Illustration 6	g06156795
Typical example of the connector for the engine intake throttle valve (3) Position sensor ground (4) Position sensor signal (5) 5 VDC supply

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

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Table 2
Troubleshooting Test Steps	Values	Results
1. Inspect Electrical Connectors and Wiring A. Turn the keyswitch to the OFF position. B. Inspect the connectors for the valve position sensors. Refer to Troubleshooting, "Electrical Connectors - Inspect". C. Perform a 45 N (10 lb) pull test on each of the wires in the suspect sensor connector and the sensor connections at the ECM. D. Check the screw for the J2 ECM connector for the correct torque of 6 N·m (53 lb in). E. Check the ground connection on the ECM for abrasions and pinch points. F. Check the harness for abrasion and pinch points from the suspect sensor to the ECM.	Loose connection or damaged wire	Result: There is a fault in a connector or the wiring. Repair: Repair any faulty connectors or replace the wiring harness. Ensure that all the seals are properly in place and ensure that the connectors are correctly coupled. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: All connectors, pins, and sockets are correctly coupled and/or inserted. The harness is free of corrosion, abrasion, and pinch points. Proceed to Test Step 2.
2. Check For Active Diagnostic Codes A. Turn the keyswitch to the OFF position. B. Connect the electronic service tool to the diagnostic connector. C. Turn the keyswitch to the ON position. Wait at least 10 seconds for activation of the diagnostic codes. D. Use the electronic service tool to monitor active diagnostic codes or recently logged diagnostic codes. E. Turn the keyswitch to the OFF position.	Diagnostic codes	Result: One or more of the preceding diagnostic codes are active or recently logged. Proceed to Test Step 3. Result: None of the preceding diagnostic codes are active or recently logged. Repair: The fault may be intermittent. Refer to Troubleshooting, "Electrical Connectors - Inspect". Perform a "Wiggle Test" by using the electronic service tool to identify intermittent connections.
3. Measure the Supply Voltage at the Valve Connector A. Turn the keyswitch to the OFF position. B. Disconnect the suspect valve from the harness. C. Turn the keyswitch to the ON position. D. Measure the voltage at the connector for the valve between terminal for the 5 VDC supply and the sensor ground terminal. E. Reconnect the valve to the harness.	4.84 to 5.16 VDC	Result: The sensor supply voltage is out of the nominal range. The fault is in the engine harness between the valve connector and the ECM. Repair: Repair the faulty valve connector or replace the faulty harness. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The sensor supply voltage is correct. Proceed to Test Step 4.
4. Measure the Supply Voltage at the 40-Pin Connector A. Turn the keyswitch to the OFF position. B. Disconnect the 40-pin connector. C. Turn the keyswitch to the ON position. D. Measure the voltage between pin 1 and pin 2 on the 40-pin connector on the harness between the engine and the CEM. E. Reconnect the 40-pin connector.	4.84 to 5.16 VDC	Result: The sensor supply voltage is out of the nominal range. The fault is in the CEM harness between the 40-pin connector and the valve. Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The voltage is not within the expected range. The CEM harness is OK. Proceed to Test Step 5.
5. Measure the Supply Voltage at the 31-Pin Connector A. Turn the keyswitch to the OFF position. B. Disconnect the 31-pin connector. C. Turn the keyswitch to the ON position. D. Measure the voltage between pin 1 and pin 2 on the 31-pin connector on the harness between the engine and the CEM. E. Reconnect the 31-pin connector.	4.84 to 5.16 VDC	Result: The sensor supply voltage is out of the nominal range. The fault is in the harness between the 40-pin connector and the 31-pin connector. Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The voltage is not within the expected range. The fault is in the engine harness between the 31-pin connector and the ECM. Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault.
6. Verify that the Diagnostic Code is Still Active A. Turn the keyswitch to the ON position. Wait at least 10 seconds for activation of the diagnostic codes. B. Use the electronic service tool to check for active diagnostic codes. Record all active diagnostic codes.	Diagnostic codes	Result: An XXXX-4 diagnostic code is active. Proceed to Test Step 7. Result: An XXXX-3 diagnostic code is active. Proceed to Test Step 10. Result: No diagnostic codes are active. An intermittent fault may exist. Repair: Use the electronic service tool to perform a "Wiggle Test". If faults are indicated, then go to the appropriate procedure.
7. Create an Open Circuit at the Valve Connector A. Turn the keyswitch to the OFF position. B. Disconnect the connector for the valve with the XXXX-4 diagnostic code. C. Remove the wire for the position sensor signal from the harness connector for the valve. D. Reconnect the connector for the valve. E. Turn the keyswitch to the ON position. Wait for at least 10 seconds for activation of the diagnostic codes. F. Use the electronic service tool to check the "Active Diagnostic Code" screen. Check for an XXXX-3 diagnostic code. G. Turn the keyswitch to the OFF position.	Open circuit	Result: An XXXX-4 diagnostic code was active before removing the signal wire. An XXXX-3 diagnostic code became active after removing the signal wire. Repair: Disconnect the connector for the valve. Reconnect the signal wire for the position sensor. Reconnect the connector for the valve. Turn the keyswitch to the ON position. Use the electronic service tool to check for active diagnostic codes. If the XXXX-4 diagnostic code returns, there is a short in the valve. Install a replacement valve. Refer to Disassembly and Assembly for the correct procedure. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: There is still a 27-4 (3407-4) or 51-4 (3515-4) diagnostic code active with the signal wire removed. The valve position sensor is OK. Repair: Return all wires to the original configuration. Proceed to Test Step 13. Result: There is still a 3488-4 (2490-4) diagnostic code active with the signal wire removed. The combustion air valve position sensor is OK. Repair: Return all wires to the original configuration. Proceed to Test Step 8.
8. Create an Open Circuit at the 40-Pin Connector A. Turn the keyswitch to the OFF position. B. Disconnect the 40-pin connector. C. Remove the wire from pin 9 on the 40-pin connector on the harness between the engine and the CEM. D. Reconnect the 40-pin connector. E. Turn the keyswitch to the ON position. Wait for at least 10 seconds for activation of the diagnostic codes. F. Use the electronic service tool to check the "Active Diagnostic Code" screen. Check for a 3488-3 (2490-3) diagnostic code. G. Turn the keyswitch to the OFF position.	Open circuit	Result: An XXXX-4 diagnostic code was active before removing the signal wire. The fault is in the CEM harness between the 40-pin connector and the combustion air valve. Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: A 3488-4 diagnostic code is still active with the signal wire removed. The CEM harness is OK. Repair: Return all wires to the original configuration. Proceed to Test Step 9.
9. Create an Open Circuit at the 31-Pin Connector A. Turn the keyswitch to the OFF position. B. Disconnect the 31-pin connector. C. Remove the wire from pin 9 on the 31-pin connector on the harness between the engine and the CEM. D. Reconnect the 31-pin connector. E. Turn the keyswitch to the ON position. Wait for at least 10 seconds for activation of the diagnostic codes. F. Use the electronic service tool to check the "Active Diagnostic Code" screen. Check for a 3488-3 (2490-3) diagnostic code. G. Turn the keyswitch to the OFF position.	Open circuit	Result: An XXXX-4 diagnostic code was active before removing the signal wire. The fault is in the harness between the 40-pin connector and the 31-pin connector. Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: A 3488-4 diagnostic code is still active with the signal wire removed. The harness between the 40-pin connector and the 31-pin connector is OK. Repair: Return all wires to the original configuration. Proceed to Test Step 13.
10. Create a Short Circuit at the Valve Connector A. Turn the keyswitch to the OFF position. B. Disconnect the connector for the valve with the XXXX-3 diagnostic code. C. Fabricate a jumper wire that is 150 mm (6 inch) long. D. Insert one end of the jumper wire into terminal 3 on the harness connector for the suspect valve. Insert the other end of the jumper into terminal 2. E. Turn the keyswitch to the ON position. F. Access the "Active Diagnostic Codes" screen on the electronic service tool and check for an active XXXX-4 diagnostic code for the suspect sensor. G. Remove the jumper.	Short circuit	Result: An XXXX-3 diagnostic code was active before the jumper was installed. An XXXX-4 diagnostic code is active when the jumper is installed. Repair: Reconnect the connector for the suspect valve. Turn the keyswitch to the ON position. Use the electronic service tool to check for active diagnostic codes. If the XXXX-3 diagnostic code returns, there is an open circuit in the valve. Install a replacement valve. Refer to Disassembly and Assembly for the correct procedure. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: A 27-3 (3407-3) or 51-3 (3515-3) diagnostic code remains active when the jumper is installed. Proceed to Test Step 13. Result: A 3488-3 (2490-3) diagnostic code remains active when the jumper is installed. The combustion air valve is OK. Proceed to Test Step 11.
11. Create a Short Circuit at the 40-Pin Connector A. Turn the keyswitch to the OFF position. B. Disconnect the 40-pin connector. C. Fabricate a jumper wire that is 150 mm (6 inch) long. D. Insert one end of the jumper wire into pin 2 on the 40-pin connector on the harness between the engine and the CEM. Insert the other end of the jumper into pin 9 on the 40-pin connector on the harness between the engine and the CEM. E. Turn the keyswitch to the ON position. F. Access the "Active Diagnostic Codes" screen on the electronic service tool and check for an active 3488-4 (2490-4) diagnostic code for the suspect sensor. Note: While the 40-pin connector is disconnected, diagnostic codes for the other components that are connected to the 40-pin connector will be active. Disregard the diagnostic codes for all the other components. Only address the 3488 (2490) diagnostic codes. G. Remove the jumper.	Short circuit	Result: A 3488-3 (2490-3) diagnostic code was active before the jumper was installed. A 3488-4 (2490-4) diagnostic code is active when the jumper is installed. The fault is in the CEM harness between the combustion air valve and the 40-pin connector. Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The 3488-3 is still active with the jumper installed. The CEM harness is OK. Reconnect the 40-pin connector. Proceed to Test Step 12.
12. Create a Short Circuit at the 31-Pin Connector A. Turn the keyswitch to the OFF position. B. Disconnect the 31-pin connector. C. Fabricate a jumper wire that is 150 mm (6 inch) long. D. Insert one end of the jumper wire into pin 2 on the 31-pin connector on the harness between the engine and the CEM. Insert the other end of the jumper into pin 9 on the 31-pin connector on the harness between the engine and the CEM. E. Turn the keyswitch to the ON position. F. Access the "Active Diagnostic Codes" screen on the electronic service tool and check for an active 3488-4 (2490-4) diagnostic code for the suspect sensor. Note: While the 40-pin connector is disconnected, diagnostic codes for the other components that are connected to the 40-pin connector will be active. Disregard the diagnostic codes for all the other components. Only address the 3488 (2490) diagnostic codes. G. Remove the jumper.	Short circuit	Result: A 3488-3 (2490-3) diagnostic code was active before the jumper was installed. A 3488-4 (2490-4) diagnostic code is active when the jumper is installed. The fault is in the harness between the 40-pin connector and the 31-pin connector. Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result: The 3488-3 (2490-3) is still active with the jumper installed. The harness between the 40-pin connector and the 31-pin connector is OK. Reconnect the 31-pin connector. Proceed to Test Step 13.
13. Bypass the Engine Wiring Harness A. Turn the keyswitch to the OFF position. B. For a 27-X (3407-X) or 51-X (3515-X) diagnostic code, perform Steps C. to F. and then continue from Step L. For a 3488-X (2490-X) diagnostic code, perform Steps G. onwards. C. Disconnect the P2 connector and the connector for the suspect valve. D. Remove the valve position sensor signal wire from the P2 connector and the connector for the suspect valve. E. Fabricate a jumper wire that is long enough to reach from the ECM to the connector for the suspect valve. F. Insert one end of the jumper wire into the plug for the signal wire on the P2 connector. Insert the other end of the jumper wire into the plug for the signal wire on the connector for the suspect valve. G. Disconnect the P2 connector and the 31-pin connector. H. Remove the wire from P2:16. Remove the wire from pin 9 on the 31-pin connector on the engine harness. I. Fabricate a jumper wire that is long enough to reach from the ECM to the 31-pin connector. J. Insert one end of the jumper into P2:16. Insert the other end of the jumper into socket 9 on the 31-pin connector on the engine harness. K. Reconnect the P2 connector and the 31-pin connector. L. Turn the keyswitch to the ON position. M. Use the electronic service tool to monitor the "Active Diagnostic Code" screen. Check for either the open or the short circuit diagnostic code for the suspect valve position sensor. N. Remove the jumpers and reconnect the wires that were previously removed. O. Reconnect the connectors.	Harness bypass	Result: The diagnostic code disappears when the jumper is installed. There is a fault in the engine wiring harness. Repair: Repair the faulty harness or replace the faulty harness. Use the electronic service tool to clear all logged diagnostic codes and verify that the repair eliminates the fault. Result:The fault is still present with the bypass installed. Contact the Dealer Solutions Network (DSN).