C7.1 Industrial Engine and Generator Set Caterpillar

Engine Pressure Sensor Open or Short Circuit - Test

Usage:

C7.1 770

System Operation Description:

This procedure covers the following codes:

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Table 1
Diagnostic Trouble Codes for the Engine Pressure Sensors
J1939 Code	Description	Notes
100-3	Engine Oil Pressure : Voltage Above Normal	The Electronic Control Module (ECM) detects the following conditions: The signal voltage from the engine oil pressure sensor is greater than 4.8 VDC for more than 8 seconds. If equipped, the warning lamp will come on. The ECM will log the diagnostic code. The ECM will set data for engine oil pressure to the default value. The default engine oil pressure is 600 kPa (87 psi). The electronic service tool will display "Voltage Above Normal" on the status screens.
100-4	Engine Oil Pressure : Voltage Below Normal	The ECM detects the following conditions: The signal voltage from the engine oil pressure sensor is less than 0.2 VDC for more than 8 seconds. The ECM has been powered for at least 2 seconds. The engine is running or the barometric pressure is greater than 55 kPa (8 psi). If equipped, the warning lamp will come on. The ECM will log the diagnostic code. The ECM will set data for the engine oil pressure to the default value. The default engine oil pressure is 600 kPa (87 psi). The electronic service tool will display "Voltage Below Normal" on the status screens.
108-3	Barometric Pressure : Voltage Above Normal	The ECM detects the following conditions: The signal voltage for the barometric pressure sensor is greater than 4.8 VDC for at least 8 seconds. If equipped, the warning lamp will come on. The ECM will log the diagnostic code.
108-4	Barometric Pressure : Voltage Below Normal	The ECM detects the following conditions: The signal voltage for the barometric pressure sensor is less than 0.2 VDC for at least 8 seconds. If equipped, the warning lamp will come on. The ECM will log the diagnostic code.
157-3	Engine Injector Metering Rail #1 Pressure : Voltage Above Normal	The ECM detects the following conditions: The signal voltage for the fuel rail pressure sensor is more than 4.7 VDC for 0.6 seconds. If equipped, the warning lamp will come on. The ECM will log the diagnostic code. The electronic service tool will display "70000 kPa" next to "Desired Fuel Rail Pressure" and "Actual Fuel Rail Pressure" on the status screens. The engine will be derated.
157-4	Engine Injector Metering Rail #1 Pressure : Voltage Below Normal	The ECM detects the following conditions: The signal voltage for the fuel rail pressure sensor is less than 0.67 VDC for 0.6 seconds. If equipped, the warning lamp will come on. The ECM will log the diagnostic code. The electronic service tool will display "70000 kPa" next to "Desired Fuel Rail Pressure" and "Actual Fuel Rail Pressure" on the status screens. The engine will be derated.
411-3	Engine Exhaust Gas Recirculation Differential Pressure : Voltage Above Normal	The ECM detects the following conditions: The signal voltage for the NOx Reduction System (NRS) differential pressure sensor is more than 4.8 VDC. The ECM has been powered for at least 0.24 seconds. If equipped, the warning light will come on. The ECM will log the diagnostic code.
411-4	Engine Exhaust Gas Recirculation Differential Pressure : Voltage Below Normal	The ECM detects the following conditions: The signal voltage for the NRS differential pressure sensor is less than 0.2 VDC. The ECM has been powered for at least 0.24 seconds. If equipped, the warning light will come on. The ECM will log the diagnostic code.
3251-3	Particulate Trap Differntial Pressure : Voltage Above Normal	The ECM detects the following conditions: The signal voltage from the Diesel Particulate Filter (DPF) differential pressure sensor is more than 4.8 VDC. If equipped, the warning light will come on. The ECM will log the diagnostic code.
3251-4	Particulate Trap Differntial Pressure : Voltage Below Normal	The ECM detects the following conditions: The signal voltage from the DPF differential pressure sensor is less than 0.2 VDC. If equipped, the warning light will come on. The ECM will log the diagnostic code.
3358-3	Engine Exhaust Gas Recirculation Inlet Pressure : Voltage Above Normal	The ECM detects the following conditions: The signal voltage from the NRS inlet pressure sensor is more than 4.8 VDC for 0.12 seconds. The ECM has been powered for 2 seconds. If equipped, the warning light will come on. The ECM will log the diagnostic code. The ECM will set data for the NRS inlet pressure to the default value. The default value for the NRS inlet pressure is 250 kPa (36.3 psi).
3358-4	Engine Exhaust Gas Recirculation Inlet Pressure : Voltage Below Normal	The ECM detects the following conditions: The signal voltage for the NRS inlet pressure sensor is less than 0.2 VDC for 0.12 seconds. The ECM has been powered for 2 seconds. If equipped, the warning light will come on. The ECM will log the diagnostic code. The ECM will set data for the NRS inlet pressure to the default value. The default value for the NRS inlet pressure is 250 kPa (36.3 psi).
3480-3	Aftertreatment #1 Fuel Pressure #1 : Voltage Above Normal	The ECM detects the following conditions: The signal voltage for the Aftertreatment Regeneration Device (ARD) pilot fuel pressure sensor is greater than 4.7 VDC for at least 2 seconds. If equipped, the warning light will come on. The ECM will log the diagnostic code. The engine will be derated. If a regeneration is in progress, the process will be stopped. Future regenerations will be prevented while the code is active.
3480-4	Aftertreatment #1 Fuel Pressure #1 : Voltage Below Normal	The ECM detects the following conditions: The signal voltage for the ARD pilot fuel pressure sensor is less than 0.2 VDC for at least 2 seconds. If equipped, the warning light will come on. The ECM will log the diagnostic code. The engine will be derated. If a regeneration is in progress, the process will be stopped. Future regenerations will be prevented while the code is active.
3563-3	Engine Intake Manifold #1 Absolute Pressure : Voltage Above Normal	The ECM detects the following conditions: The signal voltage from the intake manifold pressure sensor is above 4.8 VDC for at least 2 seconds. The ECM has been powered for 2 seconds. If equipped, the warning light will come on. The ECM will log the diagnostic code. The data for the intake manifold pressure will be set to a maximum valid pressure for 2 seconds. The ECM will then flag the intake manifold pressure as being invalid. A default value is then used for the intake manifold pressure. For engines with an electronically controlled wastegate, the current for the wastegate solenoid will be set to a default value while this code is active. This condition will cause the engine to have poor acceleration. The default setting will prevent any overpressure in the intake manifold which could be caused by an overspeed of the turbocharger.
3563-4	Engine Intake Manifold #1 Absolute Pressure : Voltage Below Normal	The ECM detects the following conditions: The signal voltage from the intake manifold pressure sensor is less than 0.2 VDC for at least 2 seconds. The ECM has been powered for 2 seconds. If equipped, the warning light will come on. The ECM will log the diagnostic code. The data for the intake manifold pressure will be set to a maximum valid pressure for 2 seconds. The ECM will then flag the intake manifold pressure as being invalid. A default value is then used for intake manifold pressure. For engines with an electronically controlled wastegate, the current for the wastegate solenoid will be set to a default value while this code is active. This condition will cause the engine to have poor acceleration. The default setting will prevent any overpressure in the intake manifold which could be caused by an overspeed of the turbocharger.
3609-3	Diesel Particulate Filter Intake Pressure 1 : Voltage Above Normal	The ECM detects the following conditions: The signal voltage from the DPF inlet pressure sensor is more than 4.95 VDC. The ECM has been powered for at least 0.24 seconds. If equipped, the warning light will come on. The ECM will log the diagnostic code.
3609-4	Diesel Particulate Filter Intake Pressure 1 : Voltage Below Normal	The ECM detects the following conditions: The signal voltage from the DPF inlet pressure sensor is less than 0.2 VDC. The ECM has been powered for at least 0.24 seconds. If equipped, the warning light will come on. The ECM will log the diagnostic code.
3837-3	Aftertreatment 1 Secondary Air Pressure : Voltage Above Normal	The ECM detects the following conditions: The signal voltage from the ARD air pressure sensor is more than 4.8 VDC. The ECM has been powered for at least 0.24 seconds. If equipped, the warning light will come on. The ECM will log the diagnostic code.
3837-4	Aftertreatment 1 Secondary Air Pressure : Voltage Below Normal	The ECM detects the following conditions: The signal voltage from the ARD air pressure sensor is less than 0.2 VDC. The ECM has been powered for at least 0.24 seconds. If equipped, the warning light will come on. The ECM will log the diagnostic code.

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

There are no active 3509 codes.
There are no active 168 codes.

The following background information is related to this procedure:

The 5 VDC sensor supply provides power to all 5 VDC sensors. The ECM supplies 5.0 ± 0.2 VDC to terminal "3" of the fuel rail pressure sensor connector and to terminal "1" of all other pressure sensor connectors. The sensor common from the ECM connector goes to terminal "1" of the connector for the fuel rail pressure sensor and to terminal "2" of all other pressure sensor connectors. The sensor supply is output short circuit protected. A short circuit to the battery will not damage the circuit inside the ECM.

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 the presence of a voltage that is above a threshold on the signal circuit, the ECM will generate an open circuit diagnostic code (XXXX-3) for the sensor.

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

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Illustration 1	g02200894
Typical example of the schematic for the pressure sensors

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Illustration 2	g01980953
Typical view of the pin locations on the P2 connector for the pressure sensors (4) Intake manifold pressure sensor signal (5) DPF inlet pressure sensor signal (6) NRS inlet pressure sensor signal (7) NRS differential pressure sensor signal (25) ARD air pressure sensor signal (26) ARD pilot fuel pressure signal sensor (27) DPF differential pressure sensor signal (34) Barometric pressure sensor signal (35) Oil pressure sensor signal (37) Fuel rail pressure sensor signal (45) Clean Emissions Module (CEM) pressure sensors 5 VDC supply (46) Oil pressure sensor 5 VDC supply (47) Engine pressure sensors 5 VDC supply (55) CEM pressure sensors ground (56) Oil pressure sensor ground (57) Engine pressure sensors ground

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Illustration 3	g02200953
Typical view of the pin locations for the pressure sensors on the connectors from the engine to the CEM (1) CEM pressure sensors 5 VDC supply (2) CEM pressure sensors ground (4) DPF inlet pressure sensor signal (7) DPF differential pressure sensor signal (8) ARD air pressure sensor signal (20) ARD pilot fuel pressure sensor signal

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Illustration 4	g01170309
Fuel rail pressure sensor (1) Ground (2) Signal (3) 5 VDC Supply

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Illustration 5	g01170310
Typical example of an engine pressure sensor (1) 5 VDC Supply (2) Ground (3) Signal

Note: The terminals on the fuel rail pressure sensor are wired differently from all other pressure sensors.

The pressure sensors are active sensors. The pressure sensors have three terminals. Active sensors require supply voltage from the ECM. The P2/J2 ECM connector supplies +5 VDC to terminal "3" of the fuel rail pressure sensor and to terminal "1" of all other pressure sensors. The common line is connected to connector "1" of the fuel rail pressure sensor and to connector "2" of all other pressure sensors. The signal voltage from terminal "2" of the fuel rail pressure sensor and from terminal "3" of all other pressure sensors is supplied to the appropriate terminal at the P2/J2 ECM connector.

Test Step 1. Inspect Electrical Connectors And Wiring

Thoroughly inspect the terminal connections on the P2/J2 ECM connectors.

Thoroughly inspect the connectors for the engine pressure sensors

Thoroughly inspect the 31-pin connector and the 40-pin connector.

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 sensor 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 sensors 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 2.
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 2. Check For Active 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

Verify if any of the diagnostic codes that are listed in Table 1 are active:

Results:

An XXXX-3 or an XXXX-4 diagnostic code is active for one or more of the pressure sensors. - Proceed to Test Step 3.
None of the preceding diagnostic codes are active. -
Repair: If the codes in Table 1 are logged, an intermittent condition may be causing the logged codes. 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 3. Check the Supply Voltage at the Sensor Connector

Turn the keyswitch to the OFF position.

Disconnect the connector for the suspect sensor.

Turn the keyswitch to the ON position. Do not start the engine.

Measure the voltage between the 5 VDC supply terminal and the ground terminal on the harness connector for the suspect sensor. The voltage measurement should be 5.0 ± 0.2 VDC.

Turn the keyswitch to the OFF position.

Reconnect the sensor.

Expected Result:

The voltage measurement is 5.0 ± 0.2 VDC.

Results:

The voltage measurement is within the expected range. - The correct supply voltage is reaching the sensor. Proceed to Test Step 6.
The voltage measurement is not within the expected range. - If the suspect sensor is on the CEM, proceed to Test Step 4.
The voltage measurement is not within the expected range. - If the suspect sensor is not on the CEM, the fault is in the 5 VDC supply wire or the ground wire in the engine wiring harness.
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. Check 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. Do not start the engine.

Measure the voltage between pin 1 and pin 2 on the 40-pin connector on the harness between the engine and the CEM. The voltage measurement should be 5.0 ± 0.2 VDC.

Turn the keyswitch to the OFF position.

Reconnect the 40-pin connector.

Results:

The voltage measurement is 5.0 ± 0.2 VDC - The fault is in the CEM harness between the 40-pin connector and the sensor connector.
Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to verify that the repair eliminates the fault.
STOP
The voltage measurement is not 5.0 ± 0.20 VDC. - The correct voltage is not reaching the 40-pin connector. Proceed to Test Step 5.

Test Step 5. Check 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. Do not start the engine.

Measure the voltage between pin 1 and pin 2 on the 31-pin connector on the engine harness. The voltage measurement should be 5.0 ± 0.2 VDC.

Turn the keyswitch to the OFF position.

Reconnect the 31-pin connector.

Results:

The voltage measurement is 5.0 ± 0.2 VDC - 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 verify that the repair eliminates the fault.
STOP
The voltage measurement is not 5.0 ± 0.20 VDC. - The correct voltage is not reaching the 31-pin connector. The fault is in the engine harness.
Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to verify that the repair eliminates the fault.
STOP

Test Step 6. Check 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.

Determine if the fault is related to an open circuit diagnostic code or a short circuit diagnostic code.

Results:

Short Circuit - A XXXX-4 diagnostic code is active for one or more of the pressure sensors at this time. Proceed to Test Step 7.
Open Circuit - A XXXX-3 diagnostic code is active for one or more of the pressure sensors 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 Sensor Connector

Turn the keyswitch to the OFF position.

Disconnect the connector for the sensor with the XXXX-4 diagnostic code.

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.

Expected Result:

An XXXX-3 diagnostic code for the disconnected sensor is now active.

Results:

An XXXX-4 diagnostic code was active before disconnecting the sensor. An XXXX-3 diagnostic code became active after disconnecting the sensor. - There may be a fault in the sensor.
Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Use the electronic service tool in order to verify that the repair eliminates the fault and then permanently install the new sensor.Use the electronic service tool in order to clear all logged diagnostic codes.
STOP
The XXXX-4 diagnostic code is still active. - If the suspect sensor is on the CEM, proceed to Test Step 8.
The XXXX-4 diagnostic code is still active. - If the suspect sensor is not on the CEM, proceed to Test Step 13.

Test Step 8. Create an Open Circuit at the 40-Pin Connector

Turn the keyswitch to the OFF position.

Disconnect the 40-pin connector.

Turn the keyswitch to the ON position. Wait at least 30 seconds for activation of the diagnostic codes.
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 diagnostic codes for the suspect sensor.

Access the "Active Diagnostic Codes" screen on the electronic service tool and check for an active XXXX-3 diagnostic code for the suspect sensor.

Turn the keyswitch to the OFF position.

Reconnect the 40-pin connector.

Results:

An XXXX-4 diagnostic code was active before disconnecting the 40-pin connector. An XXXX-3 diagnostic code for the suspect sensor became active after the 40-pin connector was disconnected - The fault is in the CEM harness.
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 XXXX-4 diagnostic code is still present - 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.

Turn the keyswitch to the ON position. Wait at least 30 seconds for activation of the diagnostic codes.
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 diagnostic codes for the suspect sensor.

Access the "Active Diagnostic Codes" screen on the electronic service tool and check for an active XXXX-3 diagnostic code for the suspect sensor.

Turn the keyswitch to the OFF position.

Reconnect the 31-pin connector.

Results:

An XXXX-4 diagnostic code was active before disconnecting the 31-pin connector. An XXXX-3 diagnostic code became active after the 31-pin connector was disconnected. - 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 XXXX-4 diagnostic code is still present - Proceed to Test Step 13.

Test Step 10. Create a Short Circuit at the Sensor Connector

Turn the keyswitch to the OFF position.

Disconnect the connector for the suspect sensor.

Fabricate a jumper wire that is 150 mm (6 inch) long. Crimp a terminal to both ends of the wire.

Use the jumper to connect the sensor signal terminal to the sensor ground terminal on the harness connector for the suspect sensor.

Turn the keyswitch to the ON position. Do not start the engine.

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. Reconnect the sensor.

Results:

An XXXX-3 diagnostic code was active before installing the jumper. An XXXX-4 diagnostic code became active with the jumper installed. - There may be a fault in the sensor.
Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Use the electronic service tool in order to verify that the repair eliminates the fault and then permanently install the new sensor.Use the electronic service tool in order to clear all logged diagnostic codes.
STOP
The XXXX-3 diagnostic code remains active when the jumper is installed - If the suspect sensor is on the CEM, proceed to Test Step 11.
The XXXX-3 diagnostic code remains active when the jumper is installed. - If the suspect sensor is not on the CEM, proceed to Test Step 13.

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.

Use the jumper to connect the suspect sensor signal pin to the sensor ground pin on the 40-pin connector on the harness between the engine and the CEM.

Turn the keyswitch to the ON position. Do not start the engine.

Access the "Active Diagnostic Codes" screen on the electronic service tool and check for an active XXXX-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 diagnostic codes for the suspect sensor.

Remove the jumper. Reconnect the 40-pin connector.

Results:

An XXXX-3 diagnostic code was active before installing the jumper. An XXXX-4 diagnostic code became active with the jumper installed. - The fault is in the CEM harness between the sensor connector 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 XXXX-3 diagnostic code is still present. - Proceed to Test Step 12.

Test Step 12. Create a Short Circuit 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.

Use the jumper to connect the suspect sensor signal pin to the sensor ground pin on the 31-pin connector on the engine harness.

Turn the keyswitch to the ON position. Do not start the engine.

Access the "Active Diagnostic Codes" screen on the electronic service tool and check for an active XXXX-4 diagnostic code for the suspect sensor.
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 diagnostic codes for the suspect sensor.

Remove the jumper. Reconnect the 31-pin connector.

Results:

An XXXX-3 diagnostic code was active before installing the jumper. An XXXX-4 diagnostic code became active with the jumper 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 XXXX-3 diagnostic code is still present. - Proceed to Test Step 13.

Test Step 13. Bypass the Signal Wire in the Engine Harness

Turn the keyswitch to the OFF position.

If the suspect sensor is on the CEM, perform the following steps:
1. Disconnect the P2 connector. Disconnect the 31-pin connector.
1. Remove the signal wire for the suspect sensor from the P2 connector. Remove the signal wire for the suspect sensor from the 31-pin connector on the engine harness.
1. Fabricate a jumper wire that is long enough to reach from the ECM to the 31-pin connector.
1. Insert one end of the jumper wire into the socket for the suspect sensor signal on the 31-pin connector on the engine harness. Insert the other end of the jumper wire into the socket for the suspect sensor signal on the P2 connector.
1. Reconnect the P2 connector. Reconnect the 31-pin connector.

If the suspect sensor is not on the CEM, perform the following steps:
1. Disconnect the P2 connector and disconnect the connector from the suspect sensor.
1. Remove the sensor signal wire from the P2 connector. Remove the signal wire from the suspect sensor connector on the engine harness.
1. Fabricate a jumper wire that is long enough to reach from the ECM to the sensor connector.
1. Insert one end of the jumper wire into the signal terminal on the suspect sensor connector on the engine harness. Insert the other end of the jumper wire into the signal socket for the suspect sensor on the P2 connector.
1. Reconnect the P2 connector. Reconnect the connector for the suspect sensor.

Turn the keyswitch to the ON position. Do not start the engine.

Access the "Active Diagnostic Codes" screen on the electronic service tool and check for active diagnostic codes for the suspect sensor.

Results:

OK - There are no active diagnostic codes for the suspect sensor at this time. The fault is in the engine harness.
Repair: Repair the faulty wiring or replace the faulty wiring. Use the electronic service tool to verify that the repair eliminates the fault.
STOP
Not OK - There is still an active diagnostic code for the suspect sensor. Remove the jumper wires. Return all wires to the original configuration.
Repair: Perform the following repair:
1. Make sure that the latest flash file for the application is installed in the ECM. Refer to Troubleshooting, "Flash Programming".
1. Contact the Technical Communicator at a Caterpillar dealer.
  Note: This consultation can greatly reduce the repair time.
1. If the Technical Communicator recommends the use of a test ECM, install a test ECM. Refer to Troubleshooting, "Replacing the ECM".
1. Turn the keyswitch to the ON position. Use the electronic service tool to verify that the repair eliminates the fault.
1. If the fault is eliminated with the replacement ECM, reconnect the suspect ECM. If the fault returns with the suspect ECM, replace the ECM.
1. If the fault is still present with the replacement ECM, do not use the replacement ECM. Contact the Technical Communicator at a Caterpillar dealer.
STOP