3176C, 3406E and 3456 Industrial Engines Troubleshooting – Sensor Signal (Analog, Active) – Test

System Operation Description:

Use this procedure to troubleshoot the electrical system if a problem is suspected with the sensors or if any one of the diagnostic codes in Table 1 is active or easily repeated.

Table 1

Diagnostic Codes Table
Code and Description	Conditions which Generate this Code	System Response
94-3 Fuel Delivery Pressure Sensor : Voltage Above Normal	The Electronic Control Module (ECM) detects signal voltage that is above normal for one second. The ECM has been powered for three seconds.	The code is logged. The ECM flags fuel pressure as invalid data.
94-4 Fuel Delivery Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for one second. The ECM has been powered for three seconds.	The code is logged. The ECM flags fuel pressure as invalid data.
100-3 Engine Oil Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for one second.	The code is logged. The value of the parameter is set to a pressure of 603 kPa (87.5 psi).
100-4 Engine Oil Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for one second.
102-0 Boost Pressure Sensor : High	The ECM detects signal voltage that is above normal for one second.	The code is logged. The value of the parameter is set to a pressure of 0 kPa (0.0 psi).
102-3 Boost Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for one second.
102-4 Boost Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for one second.
105-3 Inlet Manifold Temperature Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for one second.	The code is logged. The value of the parameter is set to a pressure of 85 °C (185.°F).
105-4 Inlet Manifold Temperature Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for one second.
108-3 Atmospheric Pressure Sensor shorted high	The ECM detects signal voltage that is above normal for one second.	The code is logged. The value of the parameter is set to a pressure of 98 kPa (14.2 psi).
108-4 Atmospheric Pressure Sensor shorted low	The ECM detects signal voltage that is below normal for one second.
110-3 Engine Coolant Temperature Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for one second.	The code is logged. The value of the parameter is set to a pressure of 90 °C (194 °F).
110-4 Engine Coolant Temperature Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for one second.
174-3 Fuel Temperature Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for one second.	The code is logged. The value of the parameter is set to a pressure of 30 °C (86 °F).
174-4 Fuel Temperature Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for one second.	The code is logged. The value of the parameter is set to a pressure of 30 °C (86 °F).
273-3 Turbocharger Outlet Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for one second.	The code is logged. The value of the parameter is set to a pressure of 0 kPa (0 psi).
273-4 Turbocharger Outlet Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for one second.	The code is logged. The value of the parameter is set to a pressure of 0 kPa (0 psi).
274-3 Atmospheric Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for one second.	The code is logged. The value of the parameter is set to a pressure of 45 kPa (6.5 psi).
274-4 Atmospheric Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for one second.	The code is logged. The value of the parameter is set to a pressure of 45 kPa (6.5 psi).

System Operation

Use this procedure to troubleshoot any suspect problems with the following pressure sensors:

 

• Fuel pressure
• Atmospheric pressure
• Engine oil pressure
• Turbocharger outlet pressure
• Auxiliary pressure

The ECM performs an automatic calibration of these sensors whenever the ECM is powered and the engine is off for at least five seconds. During an automatic calibration, the ECM calibrates pressure sensors to the value of the atmospheric pressure sensor and against an acceptable offset pressure range.

Use this procedure to troubleshoot any suspect problems with the following temperature sensors:

 

• Intake manifold air temperature
• Fuel temperature
• Coolant temperature

The supply voltage is routed to terminal A of each sensor connector. The sensor return is routed to terminal B of each sensor connector. The sensor signal is routed to terminal C of each sensor connector. The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.

The ECM continuously outputs a pull-up voltage on the input terminal from an analog sensor. The ECM uses this pull-up voltage in order to detect an open or a short in the signal circuit. When the ECM detects the presence of a voltage that is above the normal range of the sensor on the signal circuit, the ECM will generate an open circuit diagnostic code for that sensor. When the ECM detects the absence of the pull-up voltage on the signal circuit, the ECM will generate a short circuit diagnostic code for that sensor. 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.

Test Step 1. Inspect the Electrical Connectors and Wiring

 

1. Remove electrical power from the ECM.

Illustration 2 g01139425
ECM

(1) J1/P1 connectors
(2) J2/P2 connectors

Thoroughly inspect theJ1/P1 and the J2/P2 ECM connectors. Thoroughly inspect any connectors that are associated with the analog sensors. Refer to Troubleshooting, “Electrical Connectors – Inspect”.

Illustration 3 g01409393
P2 ECM connector
(P2-2) Intake manifold air temperature sensor
(P2-3) Fuel temperature sensor
(P2-8) Engine oil pressure sensor
(P2-9) Fuel pressure sensor
(P2-15) Auxiliary pressure sensor
(P2-20) Atmospheric pressure sensor
(P2-23) Turbocharger outlet pressure sensor
(P2-30) Sensor return
(P2-36) +5 VDC sensor supply

Illustration 4 g01459911
P1 ECM connector
(P1-30) Sensor return
(P1-36) +5 VDC sensor supply

Illustration 5 g01159881
Sensor connector
(A) +5 VDC sensor supply
(B) Sensor return
(C) Signal

2. 1. Check the allen head screw from each ECM connector for the proper torque. Refer to Troubleshooting, “Electrical Connectors – Inspect” for the correct torque value.

    

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the analog sensors.

    

   3. Check the harness and wiring for abrasion and for pinch points from the analog sensors to the ECM.

Expected Result:

All connectors, pins, and sockets are completely inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points. All connections and grounds are tight and free of corrosion.

Results:

 

• OK – The connectors and wiring appear to be OK. Proceed to Test Step 2. 
• Not OK – The connectors and/or wiring are not OK.Repair: Perform the necessary repairs and/or replace parts, if necessary. Refer to Troubleshooting, “Electrical Connectors – Inspect”.

  STOP

Test Step 2. Check for “Active” or for “Logged” Diagnostic Codes

 

1. Connect Caterpillar Electronic Technician (ET) to the service tool connector.

 

2. Restore electrical power to the ECM.

 

3. Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes.Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

 

4. Determine if a diagnostic code has occurred several times.Note: A diagnostic code that is logged several times is an indication of an intermittent problem. Most intermittent problems are the result of a bad connection between a socket and a pin in a connector or a bad connection between a wire and a terminal. The problem may be caused by moisture, corrosion, or wear.

 

5. Determine if the problem is active and related to one of the following diagnostic codes: 
   • -3 
   • -4 
   • -0 

Expected Result:

A diagnostic code is not active.

Results:

 

• OK – A diagnostic code is not active.Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, “Electrical Connectors – Inspect”.

  STOP

   

• Not OK – A -0, -3, or a -4 diagnostic code is active. Proceed to Test Step 3.

Test Step 3. Check the 5 Volt Supply Voltage at the Sensor Connector

 

1. Do not disconnect the connector for the suspect sensors(s).

 

2. Connect a voltmeter between pin A and pin B on the sensor side of the connector for the suspect sensor.

 

3. Measure the voltage between pin A and pin B for the suspect sensor(s).

 

4. Wiggle the harness while you monitor the voltage on the voltmeter. Perform the 45 N (10 lb) pull test on each wire in the circuit. Each terminal and each connector should easily withstand 45 N (10 lb) of tension and each wire should remain in the connector body. This test checks whether the wire was properly crimped in the terminal and whether the terminal was properly inserted into the connector.

Expected Result:

The supply voltage is approximately 5.0 ± 0.5 VDC.

Results:

 

• OK – The supply voltage is approximately 5.0 ± 0.5 VDC. An active -3 or -0 diagnostic code is present. Proceed to Test Step 4. 
• OK – The supply voltage is approximately 5.0 ± 0.5 VDC. An active -4 diagnostic code is present. Proceed to Test Step 6. 
• Not OK – The supply voltage is not approximately 5.0 ± 0.5 VDC.Repair: There is an open in the wiring or connectors between the suspect sensor(s) and the ECM. Inspect the wiring and connectors.

  STOP

Test Step 4. Check for Voltage on the Signal Wire

 

1. Measure the voltage on the harness side of the sensor connector between pin B and pin C for the suspect sensor(s).

Expected Result:

The signal voltage is less than battery voltage.

Results:

 

• OK – The signal voltage is less than battery voltage. Proceed to Test Step 5. 
• Not OK – The signal voltage is equal to battery voltage.Repair: There is a short in the harness to the Battery. Repair the wiring.

  STOP

Test Step 5. Create a Short at the Sensor Connector

 

1. Remove electrical power from the ECM.

 

2. Disconnect the suspect sensor(s).

 

3. Use a wire jumper in order to create a short between terminal C (signal) and terminal B (sensor return) at the connector for the suspect sensor(s).

 

4. Restore electrical power to the ECM.

 

5. Monitor the diagnostic codes on Cat ET. Check for an active -4 diagnostic code for the suspect sensor.Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

 

6. Remove electrical power from the ECM.

Expected Result:

A -4 diagnostic code is now active for the suspect sensor(s).

Results:

 

• OK – A -3 or -0 diagnostic code was active before creating the short at the sensor connector. A -4 diagnostic code became active after creating the short at the sensor connector. The harness and the ECM are OK. There may be a problem with the sensor.Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.

  STOP

   

• Not OK – A -3 or -0 diagnostic code is still active for the suspect sensor(s). The problem may be in the harness or with the ECM. Proceed to Test Step 7.

Test Step 6. Create an Open at the Suspect Sensor Connector

 

1. Remove electrical power from the ECM.

 

2. Disconnect the sensor connector of the suspect sensor(s) with the active 4 diagnostic code.

 

3. Restore electrical power to the ECM.

 

4. Monitor the diagnostic codes on Cat ET. Check for an active -3 or -0 diagnostic code for the suspect sensor(s).Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

 

5. Remove electrical power from the ECM.

Expected Result:

A -3 or -0 diagnostic code is now active for the suspect sensor(s).

Results:

 

• OK – A -4 diagnostic code was active before disconnecting the sensor(s). A -3 or -0 diagnostic code became active after disconnecting the sensor(s). The harness and the ECM are OK. There may be a problem with the sensor(s).Repair: Temporarily connect a new sensor(s) to the harness, but do not install the new sensor(s) in the engine. Verify that there are no active diagnostic codes for the sensor(s). If there are no active diagnostic codes for the sensor(s), permanently install the new sensor(s). Clear any logged diagnostic codes.

  STOP

   

• Not OK – A -4 diagnostic code is still active for the suspect sensor(s). Leave the sensor(s) disconnected. The problem may be in the harness or with the ECM. Proceed to Test Step 7.

Test Step 7. Test the Operation of the ECM

 

1. Fabricate jumper wires that can be used to replace the signal wire in the ECM connector for the suspect sensor(s). Crimp a connector socket to one end of the jumper wire.

 

2. Disconnect the appropriate ECM connector for the suspect sensor(s).

 

3. Remove the signal wire for the suspect sensor(s) from the ECM connector.

 

4. Install the jumper wire into the terminal location for the suspect sensor(s) at the ECM connector.

 

5. Connect the ECM connector.

 

6. Check the operation of the ECM by creating an open at the ECM: 
   1. Hold the loose end of the jumper wire away from any components in order to create an open circuit condition.

    

   2. Restore electrical power to the ECM.

    

   3. Monitor the active diagnostic code screen on Cat ET. Check for a -3 or -0 diagnostic code for the suspect sensor(s).Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

 

7. Check the operation of the ECM by creating a short circuit at the ECM: 
   1. Short the jumper wire for the suspect sensor(s) to the analog return in order to create a short circuit condition.

    

   2. Monitor the active diagnostic code screen on Cat ET. Check for a -4 diagnostic code for the suspect sensor(s).Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

 

8. Remove electrical power from the ECM.

 

9. Remove all jumper wires. Return the wiring to the original configuration.

Expected Result:

A -3 or -0 diagnostic code is active when the signal wire is removed from the ECM connector. A -4 diagnostic code is active when the signal wire is shorted to the return.

Results:

 

• OK – The ECM is operating properly. The problem is in the wiring between the ECM and the connector for the sensor(s).Repair: If the code is active for more than one sensor, the problem is most likely in the return wire for the sensor(s). Repair the analog return wire for the sensor(s) or replace the harness.If the code is only active for one sensor, the problem is most likely in the signal wire for the sensor. Repair the signal wire for the sensor.

  STOP

   

• Not OK – One of the following conditions exists: The -3 or -0 diagnostic code is not active when a signal wire is disconnected. The -4 diagnostic code is not active when the wire jumper is shorted to the analog return.Repair: Replace the ECM. Refer to Troubleshooting, “ECM – Replace”. Verify that the problem is resolved.

  STOP