C13 and C15 On-highway Engines Caterpillar

Sensor Signal (Analog, Passive) - Test

Usage:

C15 B5R

System Operation Description:

This procedure covers the following codes:

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Table 1
Diagnostic Trouble Codes for Passive Analog Sensors
J1939 Code	Description	Notes
105-3	Engine Intake Manifold 1 Temperature : Voltage Above Normal	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 -3 code. When the ECM detects voltage that is below a threshold on the signal wire, the ECM activates a -4 code. The most likely cause of these codes is a problem with an electrical connector or wiring. 15 seconds may be required in order for the ECM to activate a code after a test condition is created.
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	Air Inlet Temperature : Voltage Above Normal
172-4	Air Inlet Temperature : Voltage Below Normal
174-3	Engine Fuel Temperature : Voltage Above Normal
174-4	Engine Fuel Temperature : Voltage Below Nrmal
172-2	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.

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. 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.

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Illustration 1	g01219023
Schematic for the passive sensors

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Illustration 2	g01185721
P1 terminals for the passive sensors (P1-18) Return (P1-26) Ambient air temperature

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Illustration 3	g01219040
P2 terminals for the passive sensors (P2-30) Return (P2-38) Air inlet temperature (P2-84) Coolant temperature (P2-95) Intake manifold air temperature (P2-96) Fuel 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

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:
1. 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.
1. Insert a pin into each socket. Verify that each socket grips the pin firmly. Repair any problems.
1. Turn the keyswitch OFF.
1. Disconnect the ECM connector that relates to the code.
1. Identify the socket on the ECM connector that relates to the code. Carefully inspect the socket for proper installation. The socket must be clean and dry. Clean the socket, if necessary.
1. Insert a pin into the socket. Verify that the socket grips the pin firmly. Repair any problems.
1. Connect all connectors.
1. Turn the keyswitch ON.
1. Activate the wiggle test. Verify that the wiring passes the wiggle test.
1. 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. 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 for an Open Circuit

Disconnect the sensor that relates to the 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 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:
1. 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.
1. 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.
1. Disconnect the connectors in order to verify that the wiring and terminals are installed correctly. Make the necessary repairs.
1. 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.
STOP
No - The -3 code changes to a -4 code when the jumper wire is connected. The wiring harness is OK.
Repair: Perform the following procedure:
1. Remove the jumper wire.
1. If you are troubleshooting a -3 code, connect a new sensor to the engine harness. Do not install the sensor. A -3 code will only be generated after the engine has been running continuously for a minimum of 420 seconds. Verify that the -3 code does not recur. Then, install the sensor.
STOP

Test Step 5. Disconnect the Sensor and Check for a -3 Code

Disconnect the sensor that applies to the -4 code.

Look for a -3 code. A -3 code will only be generated after the engine has been running continuously for a minimum of 420 seconds.

Connect the sensor and look for a -4 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:
1. 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.
1. 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.
1. 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:
1. Connect a new sensor to the engine harness. Do not install the sensor into the engine.
1. Verify that the active -4 code does not recur.
1. Install the sensor into the engine.
1. Clear all logged 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:
1. Repair the connection, when possible. Replace parts, if necessary.
1. 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:
1. Replace the air inlet temperature sensor.
1. 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:
1. Connect a digital voltmeter between terminal 1 on the sensor connector and the ground strap for the ECM. Measure the DC signal voltage.
  1. 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.
  1. Verify that the DC signal voltage is between 0.2 VDC and 4.9 VDC.
STOP
A 172-4 code becomes active. -
Repair: Perform the following procedure:
1. Measure the temperature of the air inlet temperature sensor with a laser infrared thermometer or equivalent.
  1. 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.
  1. 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