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.
| Diagnostic Codes Table | ||
|---|---|---|
| Description | Conditions which Generate this Code | System Response |
| 110-3 Engine Coolant Temperature Sensor voltage above normal | The Electronic Control Module (ECM) detects signal voltage that is above normal for eight seconds. The ECM has been powered for at least two seconds. The engine has been running for seven minutes. An engine coolant temperature that is less than −35 °C (−31 °F) will also activate this fault. |
The code is logged. A snapshot is triggered. The value of the parameter is set to 90 °C (194 °F). |
| 110-4 Engine Coolant Temperature Sensor voltage below normal | The ECM detects signal voltage that is below normal for eight seconds. The ECM has been powered for at least two seconds. An engine coolant temperature that is greater than 140 °C (284 °F) will also activate this fault. |
The code is logged. A snapshot is triggered. The value of the parameter is set to 90 °C (194 °F). |
| 172-3 Intake Manifold Air Temperature Sensor voltage above normal | The ECM detects signal voltage that is above normal for eight seconds. The ECM has been powered for at least two seconds. An intake manifold air temperature that is less than −35 °C (−31 °F) will also activate this fault. |
The code is logged. A snapshot is triggered. The value of the parameter is set to 70 °C (158 °F). |
| 172-4 Intake Manifold Air Temperature Sensor voltage below normal | The ECM detects signal voltage that is below normal for eight seconds. The ECM has been powered for at least two seconds. An intake manifold air temperature that is greater than 140 °C (284 °F) will also activate this fault. |
The code is logged. A snapshot is triggered. The value of the parameter is set to 70 °C (158 °F). |
System Operation
Use this procedure to troubleshoot any suspect problems with the following sensors:
- Engine coolant temperature sensor
- Intake manifold air temperature sensor
The sensor signal for the passive sensors is routed to terminal 1 of each sensor connector. The analog return for the passive sensors is routed from the ECM to terminal 2 of each sensor connector.
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| Illustration 1 | g01339500 |
Schematic for the analog sensors | |
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| Illustration 2 | g01339501 |
Locations of the analog sensors (typical left side engine view) (1) Engine coolant temperature sensor (2) Intake manifold air temperature sensor (3) J2/P2 ECM connectors | |
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| Illustration 3 | g01339503 |
Terminal locations at the P2 ECM connector for the analog sensors (P2-13) Engine coolant temperature (P2-30) Sensor return (P2-58) Intake manifold air temperature | |
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| Illustration 4 | g01218763 |
Terminal locations at the sensor connector for the analog sensors (Terminal 1) Sensor signal (Terminal 2) Sensor return | |
Test Step 1. Check for "Active" or "Logged" Diagnostic Codes
- Connect Caterpillar Electronic Technician (ET) to the service tool connector.
- Restore power to the ECM.
- 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.
- Determine if the problem is active and related to one of the following diagnostic codes:
- 3 Voltage above normal
- 4 Voltage below normal
- 3 Voltage above normal
Expected Result:
No diagnostic codes are active at this time.
Results:
- OK - No diagnostic codes are active at this time.
Repair: There may be an intermittent electrical problem. If an intermittent electrical problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for information that is related to troubleshooting intermittent electrical problems.
STOP
- Not OK - An active 3 diagnostic code is present. Proceed to Test Step 2.
- Not OK - An active 4 diagnostic code is present. Proceed to Test Step 4.
Test Step 2. Check for a Short Circuit to the +Battery at the Sensor Connector
- Measure the voltage on the harness side of the sensor connector between pin 1 and pin 2 for the suspect sensor(s).
Expected Result:
The supply voltage is less than battery voltage.
Results:
- OK - The supply voltage is less than battery voltage. Proceed to Test Step 3.
- Not OK - The supply voltage is equal to battery voltage.
Repair: There is a short in the harness to the +Battery. Repair the harness wiring, when possible. If necessary, replace the harness.
STOP
Test Step 3. Create a Short Circuit at the Sensor Connector
- Disconnect the suspect sensor.
- Fabricate a jumper wire that is long enough to create a short circuit at the connector for the suspect sensor. Crimp connector pins to each end of the jumper wire.
- Disconnect the connector from the suspect sensor.
- Use the wire jumper in order to create a short between terminal 1 (sensor signal) and terminal 2 (analog return) at the sensor connector.
- Restore power to the ECM.
- Access the "Active Diagnostic Code" screen 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.
- Remove power from the ECM.
Expected Result:
A 4 diagnostic code is now active for the suspect sensor(s).
Results:
- OK - A 3 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.
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 diagnostic code is still active for the suspect sensor(s). Proceed to Test Step 5.
Test Step 4. Create an Open Circuit at the Connector for the Suspect Sensor
- Remove power from the ECM.
- Disconnect the sensor connector of the suspect sensor(s) with the active 4 diagnostic code.
- Restore power to the ECM.
- Access the "Active Diagnostic Code" screen on Cat ET. Check for an active 3 diagnostic code.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
- Remove power from the ECM.
Expected Result:
A 3 diagnostic code is now active for the suspect sensor(s).
Results:
- OK - A 4 diagnostic code was active before disconnecting the sensor. A 3 diagnostic code became active after disconnecting 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 4 diagnostic code is still active for the suspect sensor. There is a short circuit between the sensor connector and the ECM. Leave the sensor disconnected. Proceed to Test Step 5.
Test Step 5. Check the Operation of the ECM
- Remove power from the ECM.
- Fabricate a jumper wire that is long enough to create a test circuit between the ECM connectors and the engine ground stud. Crimp a connector socket to one end of the jumper wire.
- Disconnect the ECM connector that is for the suspect sensor. Refer to Illustration 1 for the correct terminal locations.
- Remove the signal wire for the suspect sensor from the terminal location at the ECM connector. Install the jumper wire into this terminal location.
- Reconnect the ECM connectors.
- Check the operation of the ECM by creating an open circuit at the ECM:
- Ensure that the loose end of the jumper wire is not in contact with any ground source. Restore power to the ECM.
- Monitor the "Active Diagnostic Code" screen on Cat ET.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
An open circuit diagnostic code 3 will be active for the suspect sensor.
- Check the operation of the ECM by creating a short circuit at the ECM:
- Connect the loose end of the jumper wire to the engine ground stud.
- Monitor the "Active Diagnostic Code" screen on Cat ET.
Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
A 4 diagnostic code will be active when the wire jumper is connected to the engine ground stud.
- Remove power from the ECM. Restore the wiring to the original configuration.
Expected Result:
A 3 diagnostic code is active when the sensor signal wire is removed from the ECM connector. A 4 diagnostic code is active when the signal wire is connected to engine ground.
Results:
- OK - The ECM is operating properly. The problem is in the wiring between the ECM and the sensor connector.
Repair: If the code is active for more than one sensor, the problem is most likely in the return wire for the sensor. Repair the return wire for the sensor 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 diagnostic code is not active when the sensor signal wire is disconnected. The 4 diagnostic code is not active when the wire jumper is installed.
Repair: There is a problem with the ECM. Perform the following procedure:
- Temporarily connect a test ECM.
Refer to Troubleshooting, "ECM - Replace".
- Recheck the circuit in order to ensure that the original problem has been resolved.
If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved.
If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring.
STOP
- Temporarily connect a test ECM.