This procedure covers the following codes:
| Diagnostic Trouble Codes for the Valve Position Sensors | ||
|---|---|---|
| J1939 Code | Description | Notes |
| 27-3 | Engine Exhaust Gas Recirculation 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. If equipped, 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 | Engine Exhaust Gas Recirculation 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. If equipped, the warning lamp will come on. The ECM will log the diagnostic code. The NRS valve will be fully open while the code is active. The engine will be derated. |
| 51-3 | 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 | 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 | 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 | 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 3509 codes.
- There are no active 168 codes.
Use this procedure in order 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 in order 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 | g02186415 |
Typical example of the schematic for the 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 | g01955200 |
Typical example of the connector for the combustion air valve (1) 5 VDC supply (2) Position sensor ground (3) Position sensor signal | |
 | |
| Illustration 5 | g02157941 |
Typical example of the connector for the engine intake throttle valve (3) Position sensor ground (4) Position sensor signal (5) 5 VDC supply | |
 | |
| Illustration 6 | g02854698 |
Typical example of the connector for the NRS valve (1) 5 VDC supply (2) Position sensor ground (3) Position sensor signal | |
Test Step 1. Verify All Active and Recently Logged Diagnostic Codes
- Turn the keyswitch to the ON position. Wait at least 10 seconds for activation of the diagnostic codes.
- Download the following items before performing any troubleshooting or clearing any diagnostic codes:
- Warranty Report
- Aftertreatment Regeneration Trigger History
- Product Status Report with Histograms
- Warranty Report
- Verify if any of the diagnostic codes that are listed in Table 1 are active or recently logged:
Results:
- One or more of the preceding diagnostic codes are active or recently logged. - Proceed to Test Step 2.
- 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 in order to identify intermittent connections.
STOP
Test Step 2. Inspect Electrical Connectors And Wiring
- Thoroughly inspect the terminal connections on the P2/J2 ECM connectors.
- Thoroughly inspect the connectors for the valves.
- Thoroughly inspect the 31-pin connector and the 40-pin connector.
Note: The following step is only applicable to faults with the combustion air valve.
- Refer to Troubleshooting, "Electrical Connectors - Inspect".
- Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the valve connectors that are associated with the active diagnostic code.
- Check the screw for the ECM connector for the correct torque of 6 N·m (53 lb in).
- Check the harness for abrasions and for pinch points from the valves back to the ECM.
- Use the electronic service tool to perform a "Wiggle Test". The "Wiggle Test" will identify intermittent connections.
Expected Result:
All connectors, pins, and sockets are correctly connected. The harness should be free of corrosion, abrasions, and pinch points.
Results:
- OK - Proceed to Test Step 3.
- Not OK -
Repair: Repair the connectors or the harness and/or replace the connectors or the harness. Ensure that all of the seals are correctly in place and ensure that the connectors are correctly connected.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.
STOP
Test Step 3. Measure the Supply Voltage at the Valve Connector
- Turn the keyswitch to the OFF position.
- Disconnect the suspect valve from the harness.
- Turn the keyswitch to the ON position.
- Measure the voltage at the connector for the valve from the terminal for the 5 VDC supply to the sensor ground terminal.
- Reconnect the valve to the harness.
Expected Result:
The voltage from the terminal for the 5 VDC supply to the sensor common terminal measures 4.84 to 5.16 VDC.
Results:
- OK - The sensor supply voltage is correct. Proceed to Test Step 6.
- The sensor supply voltage is out of the nominal range. - A 3488-X diagnostic code is active. Proceed to Test Step 4.
- The sensor supply voltage is out of the nominal range. - A 27-X or a 51-X diagnostic code is active. The fault is in the engine harness between the valve 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.
STOP
Test Step 4. Measure the Supply Voltage at the 40-Pin Connector
- Turn the keyswitch to the OFF position.
- Disconnect the 40-pin connector.
- Turn the keyswitch to the ON position.
- Measure the voltage between pin 1 and pin 2 on the 40-pin connector on the harness between the engine and the CEM.
- Reconnect the 40-pin connector.
Expected Result:
The voltage measures 4.84 to 5.16 VDC.
Results:
- OK - The voltage is within the expected 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.
STOP
- Not OK - The voltage is not within the expected range. The CEM harness is OK. Proceed to Test Step 5.
Test Step 5. Measure the Supply Voltage at the 31-Pin Connector
- Turn the keyswitch to the OFF position.
- Disconnect the 31-pin connector.
- Turn the keyswitch to the ON position.
- Measure the voltage between pin 1 and pin 2 on the 31-pin connector on the harness between the engine and the CEM.
- Reconnect the 31-pin connector.
Expected Result:
The voltage measures 4.84 to 5.16 VDC.
Results:
- OK - The voltage is within the expected 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.
STOP
- Not OK - 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.
STOP
Test Step 6. Verify that the Diagnostic Code is Still Active
- Turn the keyswitch to the ON position. Wait at least 10 seconds for activation of the diagnostic codes.
- Use the electronic service tool to check for active diagnostic codes. Record all active diagnostic codes.
Expected Result:
One of the diagnostic codes that are listed in Table 1 is active.
Results:
- Short Circuit - A XXXX-4 diagnostic code is active at this time. Proceed to Test Step 7.
- Open Circuit - A XXXX-3 diagnostic code is active at this time. Proceed to Test Step 10.
- A short circuit diagnostic code is not active. An open circuit diagnostic code is not 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.
STOP
Test Step 7. Create an Open Circuit at the Valve Connector
- Turn the keyswitch to the OFF position.
- Disconnect the connector for the valve with the XXXX-4 diagnostic code.
- Remove the wire for the position sensor signal from the harness connector for the valve.
- Reconnect the connector for the valve.
- Turn the keyswitch to the ON position. Wait for at least 10 seconds for activation of the diagnostic codes.
- Use the electronic service tool to check the "Active Diagnostic Code" screen. Check for an XXXX-3 diagnostic code.
- Turn the keyswitch to the OFF position.
Expected Result:
An XXXX-3 diagnostic code for the suspect sensor is now active.
Results:
- 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: Perform the following 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.
STOP
- There is still a 27-4 or 51-4 diagnostic code active with the signal wire removed. - The valve position sensor is OK. Return all wires to the original configuration. Proceed to Test Step 13.
- There is still a 3488-4 diagnostic code active with the signal wire removed. - The combustion air valve position sensor is OK. Return all wires to the original configuration. Proceed to Test Step 8.
Test Step 8. Create an Open Circuit at the 40-Pin Connector
- Turn the keyswitch to the OFF position.
- Disconnect the 40-pin connector.
- Remove the wire from pin 9 on the 40-pin connector on the harness between the engine and the CEM.
- Reconnect the 40-pin connector.
- Turn the keyswitch to the ON position. Wait for at least 10 seconds for activation of the diagnostic codes.
- Use the electronic service tool to check the "Active Diagnostic Code" screen. Check for a 3488-3 diagnostic code.
- Turn the keyswitch to the OFF position.
Expected Result:
A 3488-3 diagnostic code for the suspect sensor is now active.
Results:
- A 3488-4 diagnostic code was active before removing the signal wire. A 3488-3 diagnostic code became active after 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.
STOP
- A 3488-4 diagnostic code is still active with the signal wire removed. - The CEM harness is OK. Return all wires to the original configuration. Proceed to Test Step 9.
Test Step 9. Create an Open Circuit at the 31-Pin Connector
- Turn the keyswitch to the OFF position.
- Disconnect the 31-pin connector.
- Remove the wire from pin 9 on the 31-pin connector on the engine harness.
- Reconnect the 31-pin connector.
- Turn the keyswitch to the ON position. Wait for at least 10 seconds for activation of the diagnostic codes.
- Use the electronic service tool to check the "Active Diagnostic Code" screen. Check for a 3488-3 diagnostic code.
- Turn the keyswitch to the OFF position.
Expected Result:
A 3488-3 diagnostic code for the suspect sensor is now active.
Results:
- A 3488-4 diagnostic code was active before removing the signal wire. A 3488-3 diagnostic code became active after 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.
STOP
- 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. Return all wires to the original configuration. Proceed to Test Step 13.
Test Step 10. Create a Short Circuit at the Valve Connector
- Turn the keyswitch to the OFF position.
- Disconnect the connector for the valve with the XXXX-3 diagnostic code.
- Fabricate a jumper wire that is 150 mm (6 inch) long.
- Insert one end of the jumper wire into the terminal for the valve position sensor signal on the harness connector for the suspect valve. Insert the other end of the jumper into the terminal for the sensor ground.
- Turn the keyswitch to the ON position.
- Access the "Active Diagnostic Codes" screen on the electronic service tool and check for an active XXXX-4 diagnostic code for the suspect sensor.
- Remove the jumper.
Results:
- 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: Perform the following 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.
STOP
- A 27-3 or 51-3 diagnostic code remains active when the jumper is installed - The valve is OK. Proceed to Test Step 13.
- A 3488-3 diagnostic code remains active when the jumper is installed. - The combustion air valve is OK. Proceed to Test Step 11.
Test Step 11. Create a Short Circuit at the 40-Pin Connector
- Turn the keyswitch to the OFF position.
- Disconnect the 40-pin connector.
- Fabricate a jumper wire that is 150 mm (6 inch) long.
- 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.
- Turn the keyswitch to the ON position.
- Access the "Active Diagnostic Codes" screen on the electronic service tool and check for an active 3488-4 diagnostic code.
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 diagnostic codes.
- Remove the jumper.
Results:
- A 3488-3 diagnostic code was active before the jumper was installed. A 3488-4 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.
STOP
- 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.
Test Step 12. Create a Short at the 31-Pin Connector
- Turn the keyswitch to the OFF position.
- Disconnect the 31-pin connector.
- Fabricate a jumper wire that is 150 mm (6 inch) long.
- Insert one end of the jumper wire into pin 2 on the 31-pin connector on the engine harness. Insert the other end of the jumper into pin 9 on the 31-pin connector on the engine harness.
- Turn the keyswitch to the ON position.
- Access the "Active Diagnostic Codes" screen on the electronic service tool and check for an active 3488-4 diagnostic code.
Note: While the 31-pin connector is disconnected, diagnostic codes for the other components that are connected to the 31-pin connector will be active. Disregard the diagnostic codes for all the other components. Only address the 3488 diagnostic codes.
- Remove the jumper.
Results:
- A 3488-3 diagnostic code was active before the jumper was installed. A 3488-4 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.
STOP
- The 3488-3 is still active with the jumper installed. - The harness between the 40-pin connector and the 31-pin connector is OK. Proceed to Test Step 13.
Test Step 13. Bypass the Engine Wiring Harness
- Turn the keyswitch to the OFF position.
- For a 27-X or a 51-X diagnostic code, perform the following steps:
- Disconnect the P2 connector and the connector for the suspect valve.
- Remove the valve position sensor signal wire from the P2 connector and the connector for the suspect valve.
- Fabricate a jumper wire that is long enough to reach from the ECM to the connector for the suspect valve.
- 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.
- For a 3488 diagnostic code, perform the following steps:
- Disconnect the P2 connector and the 31-pin connector.
- Remove the wire from P2:16. Remove the wire from pin 9 on the 31-pin connector on the engine harness.
- Fabricate a jumper wire that is long enough to reach from the ECM to the 31-pin connector.
- 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.
- Reconnect the P2 connector and the 31-pin connector.
- Turn the keyswitch to the ON position.
- Use the electronic service tool in order to monitor the "Active Diagnostic Code" screen. Check for either the open or the short circuit diagnostic code for the suspect valve position sensor.
- Remove the jumpers and reconnect the wires that were previously removed.
- Reconnect the connectors.
Expected Result:
The diagnostic code disappears when the jumper is installed.
Results:
- OK - The diagnostic code disappears when the jumper is installed. There is a fault in the engine wiring harness.
Repair: Perform the following repair:
- Repair the faulty harness or replace the faulty harness.
- Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.
STOP
- Not OK - The fault is still present with the bypass installed.
Repair: Perform the following repair:
- Make sure that the latest flash file for the application is installed in the ECM. Refer to Troubleshooting, "Flash Programming".
- Contact the Technical Communicator at a Caterpillar dealer.
Note: This consultation can greatly reduce the repair time.
- If the Technical Communicator recommends the use of a test ECM, install a test ECM. Refer to Troubleshooting, "Replacing the ECM".
- Use the electronic service tool to recheck the system for active diagnostic codes.
- If the fault is resolved with the test ECM, reconnect the suspect ECM.
- If the fault returns with the suspect ECM, replace the ECM.
- Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.
STOP