This procedure covers the following diagnostic trouble codes:
Diagnostic Trouble Codes for Passive Analog Sensors     | ||
---|---|---|
J1939 Code     | Description     | Information     |
105-3     | Engine Intake Manifold 1 Temperature : Voltage Above Normal     | The Engine Control Module (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 -3 diagnostic code. When the ECM detects voltage that is below a threshold on the signal wire, the ECM activates a -4 diagnostic code. The ECM may not activate the code until a circuit fault exists for 30 seconds. During this procedure, wait for 30 seconds after you create the test condition. Then, check for the code. The most likely cause of these codes is a problem with an electrical connector or wiring.     |
105-4     | Engine Intake Manifold 1 Temperature : Voltage Below Normal     | |
110-3     | Engine Coolant Temperature : Voltage Above Normal     | |
110-4     | Engine Coolant Temperature : Voltage Below Normal     | |
171-3     | Ambient Air Temperature : Voltage Above Normal     | |
171-4     | Ambient Air Temperature : Voltage Below Normal     | |
172-3     | Engine Air Inlet Temperature : Voltage Above Normal     | |
172-4     | Engine Air Inlet Temperature : Voltage Below Normal     | |
172-2     | Engine Air Inlet Temperature : Erratic, Intermittent, or Incorrect     | The ECM checks the signal from the coolant temperature sensor whenever the engine is started. The ECM compares the temperature from the air inlet temperature sensor with the average value of the coolant temperature and the inlet manifold air temperature. If the air inlet temperature is not within 40 degrees of the average value from the other sensors, the ECM increments a counter. If the value of the counter becomes high enough, the ECM activates a 172-2 diagnostic code. The most likely cause of this code is a problem with an electrical connector or wiring.     |
171-11     | Ambient Air Temperature : Other Failure Mode     | There is a problem with the signal from the ambient air temperature sensor. The most likely cause of this code is a problem with the ambient air temperature sensor.     |
Follow the troubleshooting procedure in order to determine the root cause of these codes.     |
Diagnostics on the Caterpillar Electronic Technician (ET)
Wiggle Test - The wiggle test allows you to monitor the status of the signals from the sensors while you wiggle the wiring. This helps to identify faulty electrical connections.
Note: The wiggle test cannot be used to troubleshoot a 172-2 code.
For additional information regarding the wiggle test, refer to the documentation that accompanies your Cat ET software.
Illustration 1 | g02020815 |
Schematic for the passive sensors |
Illustration 2 | g01185721 |
P1 terminals for the passive sensors (P1-18) Return (P1-26) Ambient air temperature |
Illustration 3 | g02020853 |
Terminals on the P2 connector that relate to the passive sensors (P2-17) Return (P2-30) Return (P2-38) Air inlet temperature (P2-84) Coolant temperature (P2-95) Intake manifold air temperature |
Test Step 1. Determine if the Code is Logged or Active
Identify the code.
Results:
- 172-2 or 172-3 code - Proceed to Test Step 6.
- Logged -3 or -4 code -
Repair: Do not troubleshoot a logged code unless the code relates to an engine symptom. If the code is logged and the code does not relate to an engine symptom, clear the code.
If the code is logged and the code relates to an engine symptom, proceed to Test Step 2.
- Active -3 code - Proceed to Test Step 3.
- Active -4 code - Proceed to Test Step 5.
- Active 171-11 code -
Repair: Replace the ambient air temperature sensor. Clear the code.
STOP
Test Step 2. Wiggle the Wiring and Look for Problems
Carefully following this procedure is a good way to identify the root cause of an intermittent problem.
- Verify that the engine is OFF and that the keyswitch is ON.
- Configure Cat ET for the wiggle test. Select the status group that includes the parameter that relates to the code. Start the wiggle test.
- 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 between the P2 connector and the sensor.
As you wiggle the wiring, observe the wiring and the connectors. Look for these problems:
- Loose connectors or damaged connectors
- Moisture on the connectors or the wiring
- Damage that is caused by excessive heat
- Damage that is caused by chafing
- Improper routing of wiring
- Damaged insulation
- Loose connectors or damaged connectors
Expected Result:
The wiring failed the wiggle test.
Results:
- The wiring failed the wiggle test. -
Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.
STOP
- The wiring passed the wiggle test. -
Repair: There may be a problem inside a connector. Perform the following procedure:
- Disconnect the connectors for the sensor. Carefully inspect the terminals in each connector for proper installation. Each terminal must be clean and dry. Clean the terminals, if necessary.
- Insert a pin into each socket. Verify that each socket grips the pin firmly. Repair any problems.
- Disconnect the J2/P2 connectors.
Note: Numerous diagnostic codes will become active when you disconnect the J2/P2 connectors. Ignore the additional codes and clear the codes when you are finished.
- Identify the P2 socket that relates to the diagnostic code. Carefully inspect the socket for proper installation. The socket must be clean and dry. Clean the socket, if necessary.
- Insert a pin into the socket. Verify that the socket grips the pin firmly. Repair any problems.
- Connect all connectors.
- Activate the wiggle test. Verify that the wiring passes the wiggle test.
- Return the engine to service.
STOP
Test Step 3. Check for Battery Voltage at the Sensor's Harness Connector
Measure the voltage between terminal 1 (signal) and terminal 2 (return) on the harness connector for the sensor that relates to the code.
Expected Result:
The voltage measurement is less than the +Battery voltage.
Results:
- Yes - The voltage measurement is less than the +Battery voltage. The signal wire is not shorted to the +Battery. Proceed to Test Step 4.
- No - The voltage measurement is approximately equal to 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.
STOP
Test Step 4. Check the Signal Wire for an Open Circuit
- Disconnect the sensor that relates to the diagnostic code.
- Connect a jumper wire between terminal 1 (signal) and terminal 2 (return) on the harness connector of the sensor that relates to the code. This will replace the sensor with a short circuit.
- Wait for 15 seconds. Look for a -4 diagnostic code.
Expected Result:
The -3 code does not change to a -4 code when the jumper wire is connected.
Results:
- Yes - The -3 code does not change to a -4 code when the jumper wire is connected.
Repair: There is an open circuit in the wiring between the sensor and the P2 connector. Usually, open circuits occur near a connector or inside a connector. Perform the following procedure:
- Carefully inspect the wiring at the connector for the sensor. Pull on the wire in order to verify that the wire is crimped to the terminal and that the terminal is properly installed in the connector.
- Carefully inspect the wiring at the P2 connector. Pull on the wire in order to verify that the wire is crimped to the terminal and that the terminal is properly installed in the connector.
- Disconnect the connectors in order to verify that the wiring and terminals are installed correctly. Make the necessary repairs.
- Inspect the wiring between the connectors. Look for these problems.
- Damage that is caused by excessive heat
- Damage that is caused by chafing
- Improper routing of wiring
- Damaged insulation
Make the necessary repairs.
- Damage that is caused by excessive heat
STOP
- No - 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:
- Remove the jumper wire.
- Connect a new sensor to the engine harness. Do not install the sensor.
- Verify that the active -3 diagnostic code does not recur. A -3 code can only be generated after the engine has been running continuously for a minimum of 420 seconds.
- Install the sensor.
- Clear all logged diagnostic codes and return the engine to service.
STOP
Test Step 5. Disconnect the Sensor and Check for a -3 Diagnostic Code
- Disconnect the sensor that applies to the -4 diagnostic code.
- Look for a -3 diagnostic code. A -3 code can only be generated after the engine has been running continuously for a minimum of 420 seconds.
- Connect the sensor and look for a -4 diagnostic code.
Expected Result:
When the sensor is disconnected, the -4 code remains.
Results:
- Yes - When the sensor is disconnected, the -4 code remains. There is a problem with the wiring.
Repair: Perform the following procedure:
- Carefully inspect the wiring at the connector for the sensor. Pull on the wire in order to verify that the wire is crimped to the terminal and that the terminal is properly installed in the connector.
- Carefully inspect the wiring at the P2 connector. Pull on the wire in order to verify that the wire is crimped to the terminal and that the terminal is properly installed in the connector.
- Disconnect the connectors in order to verify that the wiring and terminals are installed correctly. Make the necessary repairs.
STOP
- No - When the sensor is disconnected, the -4 code changes to a -3 code. There is a problem with the sensor.
Repair: Perform the following procedure:
- Connect a new sensor to the engine harness. Do not install the sensor.
- Verify that the active -4 diagnostic code does not recur.
- Install the sensor.
- Clear all logged diagnostic codes and return the engine to service.
STOP
Test Step 6. Troubleshoot the 172-2 or 172-3 Diagnostic Trouble Code
Do not unplug the air inlet temperature sensor from the engine harness.
Use 7X-1710 Multimeter Probes to measure the signal voltage at the harness connector for the air inlet temperature sensor. Slide the probes into the harness connector in order to measure the signal voltage.
Expected Result:
The signal voltage is greater than 4.9 VDC.
Results:
- The signal voltage is greater than 4.9 VDC. - Proceed to Test Step 7.
- The signal voltage is between 0.2 VDC and 4.9 VDC. - Proceed to Test Step 8.
- The signal voltage is less than 0.2 VDC. - Proceed to Test Step 9.
Test Step 7. Measure the Temperature of the Air Inlet Temperature Sensor
Measure the temperature of the air inlet temperature sensor with a laser infrared thermometer or equivalent.
Expected Result:
The temperature of the sensor is above -30 °C (-22 °F).
Results:
- The temperature of the sensor is above -30 °C (-22 °F). - Proceed to Test Step 8.
- The temperature of the sensor is below -30 °C (-22 °F). -
Repair: Carefully raise the temperature of the sensor by applying heat to the sensor.Connect the engine harness to the sensor. Use 7X-1710 Multimeter Probes to measure the signal voltage at the harness connector for the air inlet temperature sensor. Slide the probes into the harness connector in order to take the voltage measurement. Verify that the DC signal voltage is between 0.2 VDC and 4.9 VDC.
STOP
Test Step 8. Check the Electrical Connections for the Sensor
- Perform a 10 pound pull test on both of the sensor wires. Repair any connections that fail the test.
- Disconnect the electrical connector from the air inlet temperature sensor. Carefully inspect the terminals on the sensor and the harness connector. Look for moisture and for corrosion.
Expected Result:
There is a problem with an electrical connection for the sensor.
Results:
- There is a problem with an electrical connection for the sensor. -
Repair: Perform the following procedure:
- Repair the connection, when possible. Replace parts, if necessary.
- Connect the sensor to the engine harness. Use 7X-1710 Multimeter Probes to measure the signal voltage at the harness connector for the air inlet temperature sensor. Slide the probes into the harness connector in order to take the voltage measurement. Verify that the DC signal voltage is between 0.2 VDC and 4.9 VDC.
STOP
- The electrical connections are OK. -
Repair: Perform the following procedure:
- Replace the air inlet temperature sensor.
- Connect the sensor to the engine harness. Use 7X-1710 Multimeter Probes to measure the signal voltage at the harness connector for the air inlet temperature sensor. Slide the probes into the harness connector in order to take the voltage measurement. Verify that the DC signal voltage is between 0.2 VDC and 4.9 VDC.
STOP
Test Step 9. Check the Sensor Wiring for a Short Circuit
- Disconnect the electrical connector from the air inlet temperature sensor. Use a jumper wire to short the terminals on the harness connector.
- Cycle the keyswitch. Then, wait for 15 seconds in order for any codes to become active.
Expected Result:
A 172-4 code does not become active.
Results:
- A 172-4 code does not become active. There is a problem with the wiring between the ECM and the harness connector for the sensor. -
Repair: Perform the following procedure in order to determine the wire that has an open circuit:
- Connect a digital voltmeter between terminal 1 on the sensor connector and the ground strap for the ECM. Measure the DC signal voltage.
- If the voltage is greater than 4.9 VDC, there is a problem with the return wire. If the voltage is less than 4.9 VDC, there is a problem with the signal wire. Check the appropriate wire for the following problems:
- Cuts
- Abrasion
- Loose connections
Make the necessary repairs.
- Cuts
- Verify that the DC signal voltage is between 0.2 VDC and 4.9 VDC.
- If the voltage is greater than 4.9 VDC, there is a problem with the return wire. If the voltage is less than 4.9 VDC, there is a problem with the signal wire. Check the appropriate wire for the following problems:
Show/hide tableIllustration 4 g01401538
2-pin connector for the ambient air temperature sensor
(1) Signal
(2) Return
STOP
- Connect a digital voltmeter between terminal 1 on the sensor connector and the ground strap for the ECM. Measure the DC signal voltage.
- A 172-4 code becomes active. -
Repair: Perform the following procedure:
- Measure the temperature of the air inlet temperature sensor with a laser infrared thermometer or equivalent.
- If the temperature of the sensor is above 135 °C (275 °F), lower the temperature of the sensor by cooling the sensor. Connect the sensor to the engine harness. Use 7X-1710 Multimeter Probes to measure the signal voltage at the harness connector for the air inlet temperature sensor. Slide the probes into the harness connector in order to take the voltage measurement. Verify that the DC signal voltage is above 0.2 VDC.
- If the temperature of the sensor is below 135 °C (275 °F), connect a new sensor to the engine harness. Use 7X-1710 Multimeter Probes to measure the signal voltage at the harness connector for the air inlet temperature sensor. Slide the probes into the harness connector in order to take the voltage measurement. Verify that the DC signal voltage is above 0.2 VDC.
STOP
- Measure the temperature of the air inlet temperature sensor with a laser infrared thermometer or equivalent.