C175-16 Petroleum Engine Caterpillar

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

Table 1

Diagnostic Codes
J1939 Code and Description	CDL Code and Description	System Response
20-3 Engine Coolant Pressure : Voltage Above Normal	2302-3 Engine Coolant Pump Outlet Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for 10 seconds. The code is logged. The value of the parameter will be set to 75 kPa (11 psi).
20-4 Engine Coolant Pressure : Voltage Below Normal	2302-4 Engine Coolant Pump Outlet Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for 10 seconds. The code is logged. The value of the parameter will be set to 75 kPa (11 psi).
94-3 Engine Fuel Delivery Pressure : Voltage Above Normal	289-3 Fuel Pressure Sensor - Before Fuel Filter voltage above normal	The ECM detects signal voltage that is above normal for 10 seconds. The ECM has been powered for 2 seconds. The code is logged. If the signal is valid, the value of the parameter will be set to the value from the fuel pressure sensor after the fuel filter. If the signal is not valid, the value of the parameter will be set to 600 kPa (87 psi).
94-4 Engine Fuel Delivery Pressure : Voltage Below Normal	289-4 Fuel Pressure Sensor - Before Fuel Filter voltage below normal	The ECM detects signal voltage that is below normal for 10 seconds. The ECM has been powered for 2 seconds. The barometric pressure must be greater than 55 kPa (8 psi) in order for this diagnostic code to be enabled. The code is logged. If the signal is valid, the value of the parameter will be set to the value from the fuel pressure sensor after the fuel filter. If the signal is not valid, the value of the parameter will be set to 600 kPa (87 psi).
94-3 Engine Fuel Delivery Pressure : Voltage Above Normal	460-3 Fuel Pressure Sensor - After Fuel Filter : Voltage Above Normal	The ECM detects signal voltage that is above normal for 8 seconds. The ECM has been powered for at least 2 seconds. The pressure for this sensor must be less than 1100 kPa (160 psi) in order for this diagnostic code to be enabled. The code is logged. The value of the parameter will be set to 15 kPa (2 psi) less than the value from the fuel pressure sensor before the fuel filter.
94-4 Engine Fuel Delivery Pressure : Voltage Below Normal	460-4 Fuel Pressure Sensor - After Fuel Filter : Voltage Below Normal	The ECM detects signal voltage that is below normal for 8 seconds. The ECM has been powered for 2 seconds. The barometric pressure must be greater than 55 kPa (8 psi) in order for this diagnostic code to be enabled. The code is logged. The value of the parameter will be set to 15 kPa (2 psi) less than the value from the fuel pressure sensor before the fuel filter.
100-3 Engine Oil Pressure Sensor : Voltage Above Normal	100-3 Engine Oil Pressure : Voltage Above Normal	The Electronic Control Module (ECM) detects signal voltage that is above normal for 8 seconds. The ECM has been powered for at least 2 seconds. Engine speed equals 0 rpm or the engine coolant temperature is less than 38 °C (100 °F). The code is logged. If the signal is valid, the parameter will use the value from the sensor for the unfiltered oil pressure. If the signal is not valid, the value of the parameter will be set to 600 kPa (87 psi).
100-4 Engine Oil Pressure Sensor : Voltage Below Normal	100-4 Engine Oil Pressure : Voltage Below Normal	The ECM detects signal voltage that is below normal for 8 seconds. The ECM has been powered for 2 seconds. The barometric pressure must be greater than 55 kPa (8 psi) in order for this diagnostic code to be enabled. The code is logged. If the signal is valid, the parameter will use the value from the sensor for the unfiltered oil pressure. If the signal is not valid, the value of the parameter will be set to 600 kPa (87 psi).
101-3 Crankcase Air Pressure Sensor : Voltage Above Normal	101-3 Engine Crankcase Pressure : Voltage Above Normal	The ECM detects signal voltage that is above normal for 30 seconds. The ECM has been powered for 2 seconds. The code is logged. The value of the parameter will be set to the value from the barometric pressure sensor.
101-4 Crankcase Air Pressure Sensor : Voltage Below Normal	101-4 Engine Crankcase Pressure : Voltage Below Normal	The ECM detects signal voltage that is below normal for 30 seconds. The ECM has been powered for 2 seconds. The code is logged. The value of the parameter will be set to the value from the barometric pressure sensor.
102-3 Engine Intake Manifold #1 Pressure : Voltage Above Normal	1785-3 Intake Manifold Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for 10 seconds. The code is logged. The value of the parameter will be set to 320 kPa (46 psi).
102-4 Engine Intake Manifold #1 Pressure : Voltage Below Normal	1785-4 Intake Manifold Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for 10 seconds. The value of the parameter for the barometric pressure must be greater than 55 kPa (8 psi) in order for this diagnostic code to be enabled. The code is logged. The value of the parameter will be set to 320 kPa (46 psi).
108-3 Barometric Pressure : Voltage Above Normal	274-3 Atmospheric Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for 30 seconds. The ECM has been powered for 2 seconds. The code is logged. The pressure value for the parameter is set by using Smart Barometric Pressure Default Strategy.
108-4 Barometric Pressure : Voltage Below Normal	274-4 Atmospheric Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is above normal for 30 seconds. The ECM has been powered for 2 seconds. The code is logged. The pressure value for the parameter is set by using Smart Barometric Pressure Default Strategy.
109-3 Engine Coolant Pressure : Voltage Above Normal	2303-3 Engine Block Coolant Outlet Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for 10 seconds. The code is logged. The value of the parameter will be set to 35 kPa (5 psi).
109-4 Engine Coolant Pressure : Voltage Below Normal	2303-4 Engine Block Coolant Outlet Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for 10 seconds. The code is logged. The value of the parameter will be set to 35 kPa (5 psi).
1176-3 Engine Turbocharger 1 Compressor Inlet Pressure : Voltage Above Normal	2738-3 Turbocharger #1 Compressor Inlet Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for 20 seconds. The code is logged. An average pressure is calculated from the other turbocharger compressor inlet pressure sensors. The value of this parameter will be set to the calculated value.
1176-4 Engine Turbocharger 1 Compressor Inlet Pressure : Voltage Below Normal	2738-4 Turbocharger #1 Compressor Inlet Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for 20 seconds. The code is logged. An average pressure is calculated from the other turbocharger compressor inlet pressure sensors. The value of this parameter will be set to the calculated value.
1177-3 Engine Turbocharger 2 Compressor Inlet Pressure : Voltage Above Normal	2739-3 Turbocharger #2 Compressor Inlet Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for 20 seconds. The code is logged. An average pressure is calculated from the other turbocharger compressor inlet pressure sensors. The value of this parameter will be set to the calculated value.
1177-4 Engine Turbocharger 2 Compressor Inlet Pressure : Voltage Above Normal	2739-4 Turbocharger #2 Compressor Inlet Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for 20 seconds. The code is logged. An average pressure is calculated from the other turbocharger compressor inlet pressure sensors. The value of this parameter will be set to the calculated value.
1203-3 Engine Auxiliary Coolant Pressure : Voltage Above Normal	2301-3 Aftercooler Coolant Pump Outlet Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal for 10 seconds. The code is logged. The value of the parameter will be set to 35 kPa (5 psi).
1203-4 Engine Auxiliary Coolant Pressure : Voltage Below Normal	2301-4 Aftercooler Coolant Pump Outlet Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal for 10 seconds. The code is logged. The value of the parameter will be set to 35 kPa (5 psi).
1208-3 Engine Pre-filter Oil Pressure : Voltage Above Normal	542-3 Engine Oil Pressure Sensor - Before Oil Filter : Voltage Above Normal	The ECM detects signal voltage that is above normal for 8 seconds. The ECM has been powered for at least 2 seconds. The pressure for this sensor must be less than 1100 kPa (160 psi) in order for this diagnostic code to be enabled. The code is logged. The value of the parameter will be set to 600 kPa (87 psi).
1208-4 Engine Pre-filter Oil Pressure : Voltage Below Normal	542-4 Engine Oil Pressure Sensor - Before Oil Filter : Voltage Below Normal	The ECM detects signal voltage that is below normal for 8 seconds. The ECM has been powered for 2 seconds. The barometric pressure must be greater than 55 kPa (8 psi) in order for this diagnostic code to be enabled. The code is logged. The value of the parameter will be set to 600 kPa (87 psi).
1382-3 Engine Fuel Filter (suction side) Differential Pressure : Voltage Above Normal	3418-3 Fuel Filter (suction side) Differential Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal. The code is logged.
1382-4 Engine Fuel Filter (suction side) Differential Pressure : Voltage Below Normal	3418-4 Fuel Filter (suction side) Differential Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal. The code is logged.
1797-3 Fuel Rail Pressure Sensor : Voltage Above Normal	157-3 Engine Injector Metering Rail 1 Pressure : Voltage Above Normal	The ECM detects signal voltage that is above normal. The code is logged. The engine power is derated to a default torque map while the code is active.
1797-4 Fuel Rail Pressure Sensor : Voltage Below Normal	157-4 Engine Injector Metering Rail 1 Pressure : Voltage Below Normal	The ECM detects signal voltage that is below normal. The code is logged. The engine power is derated to a default torque map while the code is active.
1797-7 Fuel Rail Pressure Sensor : Not Responding Properly	157-7 Engine Injector Metering Rail 1 Pressure : Not Responding Properly	The ECM detects an unstable signal voltage from the sensor. The code is logged. The engine power is derated to a default torque map while the code is active.
5417-3 Primary Fuel Filter Inlet Pressure Sensor: Voltage Above Normal	3417-3 Fuel Filter (suction side) Intake Pressure Sensor : Voltage Above Normal	The ECM detects signal voltage that is above normal. The code is logged.
5417-4 Primary Fuel Filter Inlet Pressure Sensor: Voltage Below Normal	3417-4 Fuel Filter (suction side) Intake Pressure Sensor : Voltage Below Normal	The ECM detects signal voltage that is below normal. The code is logged.

Schematics (Primary ECM)

Illustration 1	g02588616
Schematic for the primary analog sensors that are shown in the right side engine view if equipped with an A4 ECM

Illustration 2	g06320899
Schematic for the primary analog sensors that are shown in the right side engine view if equipped with an A5 ECM

Illustration 3	g02590137
Schematic for the primary analog sensors that are shown in the front engine view if equipped with an A4 ECM

Illustration 4	g06320909
Schematic for the primary analog sensors that are shown in the front engine view if equipped with an A5 ECM

Illustration 5	g02590257
Schematic for the primary analog sensors that are shown in the top engine view if equipped with an A4 ECM

Illustration 6	g06321948
Schematic for the primary analog sensors that are shown in the top engine view if equipped with an A5 ECM

System Operation (Secondary ECM)

This engine utilizes a redundant control system in the case of an ECM failure. If the primary ECM fails, the secondary ECM provides for engine control and engine system monitoring. The secondary ECM utilizes several additional active sensors to monitor engine operation. The following sensors can be found on the engine and are only utilized by the secondary ECM during a failure of the primary ECM:

• Secondary atmospheric pressure sensor

• Secondary intake manifold pressure sensor

• Secondary coolant pressure sensor for the inlet of the engine block

• Secondary filtered oil pressure sensor

• Secondary fuel transfer pressure sensor (filtered)

• Secondary fuel rail pressure sensor

When troubleshooting these sensors, ensure that the secondary ECM is controlling the engine. Except for the secondary fuel rail pressure sensor, each sensor utilizes the same diagnostic code as the primary version of the sensor. The troubleshooting procedure for each secondary active sensor is the same as the troubleshooting for the primary active sensors.

Sensor Locations (Secondary ECM)

Illustration 7	g02591104
Locations of the secondary analog sensors (right side engine view) (14) Secondary fuel transfer pressure sensor (filtered)

Illustration 8	g02783941
Locations of the secondary analog sensors (front engine view) (15) Secondary atmospheric pressure sensor (16) Secondary coolant pressure sensor for the inlet of the engine block

Illustration 9	g02591139
Locations of the secondary analog sensors (top engine view) (17) Secondary fuel rail pressure sensor (18) Secondary intake manifold pressure sensor (19) Secondary filtered oil pressure sensor

Schematics (Secondary ECM)

Illustration 10	g02590938
Schematic for the secondary analog sensors equipped with A4 ECM

Illustration 11	g06321957
Schematic for the secondary analog sensors equipped with A5 ECM

Illustration 12	g02784321
Schematic for the secondary analog sensors equipped with A4 ECM

Illustration 13	g06321987
Schematic for the secondary analog sensors equipped with A5 ECM

Illustration 14	g02784216
Schematic for the secondary analog sensors for both A4 ECM and A5 ECM

Background Information

The ECM continuously creates a pull-up voltage on the signal wire for each sensor. The ECM uses this pull-up voltage in order to detect a problem in the signal circuit. When the ECM detects voltage that is above a threshold on the signal wire, the ECM activates a high voltage -3 diagnostic code. When the ECM detects voltage that is below a threshold on the signal wire, the ECM activates a low voltage -4 diagnostic code.

Note: There may be a delay of 30 seconds in order for Cat^® Electronic Technician (ET) to display an active diagnostic code. When you check for a diagnostic code, be sure to wait at least 30 seconds.

The following components can cause these codes:

• Electrical connector or wiring

• Sensor

• ECM

The most likely cause of a code is a problem with an electrical connector or wiring. The least likely cause of a code is the ECM.

Table 2

Troubleshooting Test Steps	Values	Results
1. Determine if the Code is Logged or Active A. Connect Cat ET to the service tool connector. B. Restore electrical power to the engine ECM. C. Monitor the active diagnostic code and the logged diagnostic codes on Cat ET. Note. Wait at least 30 seconds in order for diagnostic codes to become active. D. Identify the diagnostic code.	Active or logged code	Results: Logged code Repair: Do not troubleshoot a logged code unless the code relates to an operator complaint. If the code is logged and the code does not relate to an operator complaint, clear the code. If the code is logged and the code relates to an operator complaint. Proceed to Test Step 2 Results: Active code Proceed to Test Step 3

Table 3

2. Check the Integrity of the Connections at the Connectors A. Restore the electrical power to the ECM. Do not start the engine. B. Install a 7X-1708 Multimeter Probe (RED) and a 7X-1709 Multimeter Probe (BLACK) onto the test leads of a multimeter. Note: Ensure that the multimeter probes are in good repair. Bent probes may contact other terminals inside the connector. C. Check for an intermittent problem at the connector for the suspect sensor: Note: Do not disconnect any harness connectors in order to perform this procedure. a. Carefully install the spoons (multimeter probes) into the terminal locations for the sensor supply and the sensor return at the appropriate ECM connector. b. While you observe the voltage reading on the multimeter, wiggle the wires and pull on the wires at the connector for the suspect sensor. The voltage reading will not vary more than 0.5 V for a solid electrical connection. c. Remove the spoons (multimeter probes) from the connector. D. Check for an intermittent problem at the ECM connector: Note: Do not disconnect any harness connectors in order to perform this procedure. a. Carefully install the spoons (multimeter probes) into the terminal locations for the sensor supply and the sensor return at the connector for the suspect sensor. b. Observe the voltage reading on the multimeter. Wiggle the harness and pull on the wires for the sensor supply and the sensor return at the ECM connector. The voltage reading will not vary more than 0.5 V for a solid electrical connection. c. Remove the spoons (multimeter probes) from the connector. E. Remove the electrical power from the ECM.

0.5V Tolerance

Results: The voltage reading did not vary more than 0.5 V. Repair: The connections are OK at the connectors. There does not appear to be an intermittent problem in the circuit at this time. Return the engine to service. Results: At least one of the voltage reading varied more than 0.5 V during the test. Repair: Disconnect the suspect connector and inspect the connector and the terminals for moisture, damage, and corrosion. Repair the connectors and/or the terminals. Return the engine to service.

Table 4

3. Check the Supply Voltage at the Sensor Connector A. Measure the voltage between terminal 1 (sensor supply) and terminal 2 (sensor return) at the harness connector for the sensor that relates to the code.	S4.5 to 5.5VDC	Results: The voltage is between 4.5 VDC and 5.5 VDC. The supply voltage is at the sensor connector. Record the voltage measurement. If you are troubleshooting a -3 diagnostic code. Proceed to Test Step 4 If you are troubleshooting a -4 diagnostic code. Proceed to Test Step 7 Results: The voltage is less than 4.5 VDC or the voltage is greater than 5.5 VDC. Repair: The voltage of the sensor supply is incorrect. Refer to Troubleshooting, "Sensor Supply"
4. Check for Battery Voltage on the Signal Wire A. Measure the voltage between the signal terminal and the return terminal on the harness connector for the sensor that relates to the diagnostic code.	Battery voltage	Results: The voltage measurement is less than the +Battery voltage. The signal wire is not shorted to the +Battery. Proceed to Test Step 5 Results: The voltage measurement is approximately the +Battery voltage. The signal wire is shorted to the +Battery. Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.
5. Check the Signal Wire for an Open Circuit A. Disconnect the sensor that relates to the diagnostic code. B. Connect a jumper wire between the signal terminal and the return terminal on the harness connector for the sensor that relates to the diagnostic code. This jumper will replace the sensor with a short circuit. C. Look for a -4 diagnostic code.	Open circuit	Results: The -3 code does not change to a -4 code when the jumper wire is connected. Connect the sensor. There is a problem with the wiring harness or with the ECM. Proceed to Test Step 6 Results: The -3 code changes to a -4 code when the jumper wire is connected. The wiring harness and the ECM are OK. Repair: Perform the following procedure: 1. Remove the jumper wire. 2. Connect a new sensor to the engine harness. Do not install the sensor into the engine. 3. Verify that the active -3 diagnostic code does not recur. 4. Install the sensor into the engine. 5. Clear all logged diagnostic codes and return the engine to service.
6. Check the ECM for Proper Operation A. Determine the terminal location at the appropriate ECM connector for the signal and return wires of the suspect sensor. B. Remove the signal terminal and the return terminal from the ECM connector. C. Install a jumper wire between the terminal locations for the signal and the return at the ECM connector. This jumper will replace the engine wiring with a short circuit. D. Look for a -4 diagnostic code.	ECM	Results: A -4 code is active when the jumper wire is installed. The ECM detected the jumper wire at the ECM connector. However, the ECM did not detect the jumper wire at the harness connector for the sensor. There is an open circuit in the wiring. Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved. Results: A -4 code is not active when the jumper wire is installed. Repair: The ECM does not detect the jumper wire at the ECM connector. There appears to be a problem with the ECM. Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance.
7. Check the Signal Wire for a Short Circuit A. Disconnect the sensor that applies to the -4 diagnostic code. B. Look for a -3 diagnostic code. C. Connect the sensor and look for a -4 diagnostic code.	Short circuit	Results: When the sensor is disconnected, the -4 code remains. There is a problem with the wiring harness or with the ECM. Proceed to Test Step 8 Results: When the sensor is disconnected, the -4 code changes to a -3 code. Repair: Perform the following procedure: 1. Connect a new sensor to the engine harness. Do not install the sensor into the engine. 2. Verify that the active -4 diagnostic code does not recur. 3. Install the sensor into the engine. 4. Clear all logged diagnostic codes and return the engine to service.
8. Check the ECM for Proper Operation A. Determine the terminal location at the appropriate ECM connector for the signal wire of the suspect sensor. B. Remove the signal wire from the ECM connector. C. Check if the -4 diagnostic code becomes an active -3 active code.	ECM	Results: A -3 code is active when the signal wire is disconnected from the connector at the ECM. The ECM detected the open circuit at the ECM connector. However, the ECM did not detect the open circuit at the harness connector for the sensor. There is a problem with the wiring between the ECM connector and the harness connector for the sensor. There may be a problem with a connector. Repair: Repair the wiring or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved. Results: A -3 code is not active when the signal wire is disconnected from the ECM connector. The ECM did not detect the open circuit at the ECM connector. There is a problem with the ECM. Repair: The ECM does not detect the open circuit at the ECM connector. There appears to be a problem with the ECM. Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance.