C4.4 and C7.1 Engines Sensor Signal (Analog, Active) - Test Caterpillar


Sensor Signal (Analog, Active) - Test
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For Engines Equipped With A4E2 Electronic Control Module

This procedure covers the following diagnostic codes:

Table 1
Diagnostic Trouble Codes 
J1939 Code  CDL Code  Code Description  Comments 
100-3  100-3  Engine Oil Pressure Sensor : 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.

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  100-4  Engine Oil Pressure Sensor : 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 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. 
157-3  1797-3  Fuel Rail Pressure Sensor : Voltage Below 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.

The warning lamp will flash. 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  1797-4  Fuel Rail Pressure Sensor : Current 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.

The warning lamp will flash. 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. 
1381-3  2247-3  Fuel Transfer Pump Intake Pressure Sensor : Voltage Above Normal  The Electronic Control Module (ECM) detects the following conditions:

The signal voltage from the primary fuel filter outlet pressure sensor is greater than 4.8 VDC for more than 8 seconds.

The warning lamp will come on. The ECM will log the diagnostic code. The electronic service tool will display "Voltage Above Normal" on the status screens. 
1381-4  2247-4  Fuel Transfer Pump Intake Pressure Sensor : Voltage Below Normal  The ECM detects the following conditions:

The signal voltage from the primary fuel filter outlet pressure sensor is less than 0.2 VDC for more than 8 seconds.

The ECM has been powered for at least 2 seconds.

The warning lamp will come on. The ECM will log the diagnostic code. The electronic service tool will display "Voltage Below Normal" on the status screens. 
3563-3  1785-3  Intake Manifold Pressure Sensor : 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 8 seconds.

The ECM has been powered for 2 seconds.

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.
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  1785-4  Intake Manifold Pressure Sensor : 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 8 seconds.

The ECM has been powered for 2 seconds.

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.
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. 
5578-3  289-3  Fuel Pressure Sensor - Before Fuel Filter : Voltage Above Normal  The Electronic Control Module (ECM) detects the following conditions:

The signal voltage from the secondary fuel filter inlet pressure sensor is greater than 4.8 VDC for more than 8 seconds.

The warning lamp will come on. The ECM will log the diagnostic code. The electronic service tool will display "Voltage Above Normal" on the status screens. 
5578-4  289-4  Fuel Pressure Sensor - Before Fuel Filter : Voltage Below Normal  The ECM detects the following conditions:

The signal voltage from the secondary fuel filter inlet pressure sensor is less than 0.2 VDC for more than 8 seconds.

The ECM has been powered for at least 2 seconds.

The warning lamp will come on. The ECM will log the diagnostic code. The electronic service tool will display "Voltage Below Normal" on the status screens. 
5580-3  460-3  Fuel Pressure Sensor - After Fuel Filter : Voltage Above Normal  The Electronic Control Module (ECM) detects the following conditions:

The signal voltage from the secondary fuel filter outlet pressure sensor is greater than 4.8 VDC for more than 8 seconds.

The warning lamp will come on. The ECM will log the diagnostic code. The electronic service tool will display "Voltage Above Normal" on the status screens. 
5580-4  460-4  Fuel Pressure Sensor - After Fuel Filter : Voltage Below Normal  The ECM detects the following conditions:

The signal voltage from the secondary fuel filter outlet pressure sensor is less than 0.2 VDC for more than 8 seconds.

The ECM has been powered for at least 2 seconds.

The warning lamp will come on. The ECM will log the diagnostic code. The electronic service tool will display "Voltage Below Normal" on the status screens. 
Follow the troubleshooting procedure in order to identify the root cause of the fault. 

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

  • There are no active 262 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 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. The sensor common from the ECM connector goes 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 a voltage above a threshold on the signal circuit, an open circuit diagnostic code (XXXX-3) is generated for the sensor.

If the sensor is disconnected, pull-up voltage indicates that the wires from the sensor connector to the ECM 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.



Illustration 1g03506662
Schematic for the pressure sensors on the P1 connector
Not all connectors are shown. Refer to the Electrical Schematic for the application.


Illustration 2g03374199
Schematic for the pressure sensors on the P2 connector


Illustration 3g03506663
Pin locations on the P1 connector for the pressure sensors
(33) Fuel pressure sensor ground
(42) Fuel pressure sensor 5 VDC supply
(54) Inlet fuel pressure sensor signal
(55) Outlet fuel pressure sensor signal
(56) Primary fuel pressure sensor signal


Illustration 4g03374218
Pin locations on the P2 connector for the pressure sensors
(38) Intake manifold pressure sensor ground
(39) Oil pressure sensor ground
(40) Fuel rail pressure sensor ground
(46) Intake manifold pressure sensor 5 VDC supply
(47) Oil pressure sensor 5 VDC supply
(48) Fuel rail pressure sensor 5 VDC supply
(49) Fuel rail pressure sensor signal
(55) Intake manifold pressure sensor signal
(56) Oil pressure sensor signal


Illustration 5g03374231
Fuel rail pressure sensor
(1) Ground
(2) Signal
(3) 5 VDC Supply


Illustration 6g01170310
Typical example of an engine pressure sensor
(1) 5 VDC Supply
(2) Ground
(3) Signal

Table 2
Troubleshooting Test Steps  Values  Results 

1. Check for Diagnostic Codes

A. Establish communication between the electronic service tool and the ECM . Refer to Troubleshooting, "Electronic Service Tools", if necessary.

B. Turn the keyswitch to the ON position.

C. Look for a -3, or -4 active or logged codes:
 

Diagnostic code
 

Result: A -3 diagnostic code is active.

Proceed to Test Step 2.

Result: A -4 diagnostic code is active.

Proceed to Test Step 3.
 

2. Create a Short at the Sensor Connector

A. Use a jumper wire in order to create a short between the signal terminal and the ground terminal at the sensor connector.

B. Turn the keyswitch to the ON position.

C. Monitor the diagnostic codes on the electronic service tool. Check for an active -4 diagnostic code for the suspect sensor.

D. Turn the keyswitch to the OFF position.
 

Short created
 

Result: A -4 diagnostic code became active after creating the short at the sensor connector.

The wiring is OK. Replace the sensor.
Verify that the problem is resolved.

Result: A -4 diagnostic code does not become active for the suspect sensor.

Proceed to Test Step 4.
 

3. Create an Open at the Suspect Sensor Connector

A. Turn the keyswitch to the OFF position.

B. Disconnect the sensor connector of the suspect sensor with the active -4 diagnostic code.

C. Turn the keyswitch to the ON position.

D. Monitor the diagnostic codes on the electronic service tool. Check for an active -3 diagnostic code for the suspect sensor.

E. Turn the keyswitch to the OFF position.
 

Create an Open 

Result: A -3 diagnostic code became active after disconnecting the sensor.

The wiring is OK. Replace the sensor.

Verify that the problem is resolved.

Result: A -3 diagnostic code did not became active after disconnecting the sensor.

Proceed to Test Step 4.
 

4. Check the 5 VDC Supply Voltage at the Sensor Connector

A. Turn the keyswitch to the ON position.

B. Measure the voltage between the sensor supply pin and the sensor return pin at the suspect sensor.
 

Test passed 

Result: The supply voltage is approximately 5.0 ± 0.2 VDC

Connect the sensor and then proceed to Test Step 5

Result: The supply voltage is not approximately 5.0 ± 0.2 VDC.

There is a short in the harness to the battery. Repair the wiring or replace the harness

Verify that the problem is resolved.
STOP
 

5. Perform the Wiggle Test

Carefully following this procedure is the best way to identify the root cause of an intermittent problem.

A. Turn the keyswitch to the ON position.

B. Use the electronic service tool to run the "Wiggle Test".

C. Slowly wiggle the wiring and the connectors between the P2 connector and the sensor. Pay particular attention to the wiring near each connector. Be sure to wiggle all of the wiring.
As you wiggle the wiring look for these problems.
1. Loose connectors or damaged connectors
2. Moisture on the connectors or the wiring
3. Damaged that is caused by excessive heat
4. Damage that is caused by chafing
5. Improper routing of wiring
6. Damaged insulation
 

Test passed 

Result: The wiring failed the Wiggle Test.

There is a problem with the wiring. Repair the wiring or replace the wiring.

Verify that the problem is resolved.

STOP

Result: The wiring passed the Wiggle Test.

The problem may be intermittent. Inspect the wiring. Refer to Troubleshooting, "Electrical Connectors - Inspect".

If the wiring looks OK perform the following procedure.

1. Turn the keyswitch to the OFF position.
2. Disconnect the connectors. Carefully inspect the terminals for proper installation. Make sure that each terminal is clean and dry.
3. Insert a pin into each socket. Verify that each socket grips the pin firmly. Repair any problems.
4. Connect all connectors.
5. Verify that the problem is resolved.
6. Return the unit to service.
STOP