Use this procedure to troubleshoot the electrical system if a problem is suspected with the engine oil temperature sensor or if any one of the diagnostic codes in Table 1 is active or easily repeated.
| Diagnostic Codes Table | ||
|---|---|---|
| Code and Description | Conditions which Generate this Code | System Response |
| 175-3 Engine Oil Temperature Sensor : Voltage Above Normal | The engine's Electronic Control Module (ECM) detects signal voltage that is more than 4.8 VDC for one second.
The ECM has been powered for at least three seconds. |
The code is logged.
The value of the parameter is set to zero. |
| 175-4 Engine Oil Temperature Sensor : Voltage Below Normal | The ECM detects signal voltage that is less than 0.2 VDC for one second.
The ECM has been powered for at least three seconds. |
|
System Operation
Both the primary ECM and the secondary ECM can provide analog sensor reference to the engine sensors. In normal operation, the primary ECM has control of the engine. The primary ECM will provide the analog sensor reference to the engine sensors. If the secondary ECM must take over control of the engine, the secondary ECM will provide the analog sensor reference to the engine sensors. The analog sensor reference to the engine sensor is switched between the primary ECM and secondary ECM by the relay panel that is mounted on the left side of the engine. When the secondary ECM assumes control of the engine, the sinking driver for the "Backup ECM Active Lamp" is activated. When the sinking driver for the "Backup ECM Active Lamp" is activated, the reference relay in the relay panel is energized. When the reference relay is energized, the analog sensor reference to the engine sensors is switched from the primary ECM to the secondary ECM.
The sensor signal for the passive sensors is routed to terminal C of the sensor connector. The analog sensor reference for the passive sensor is routed to terminal B of the sensor connector.
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| Illustration 1 | g01627094 |
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Typical schematic | |
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| Illustration 2 | g01627228 |
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| Illustration 3 | g01242612 |
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P1 ECM connector (P1-3) "Analog sensor reference" (P1-54) Engine oil temperature sensor | |
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| Illustration 4 | g01341888 |
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Terminal locations for the A-C1/E-C2/E-C1 Right hand cross over harness (Terminal B) "Analog sensor reference" (Terminal H) Engine oil temperature | |
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| Illustration 5 | g01341865 |
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Sensor connector (Terminal C) Sensor signal (Terminal B) "Analog sensor reference" | |
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| Illustration 6 | g01622856 |
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Connector locations (1) A-C1/E-C2/E-C1 Right hand cross over harness (2) A-C2/J-C2/J-C1 Right hand cross over harness (3) A-C90/P-C1 Connectors for the power distribution panel (4) A-C91/P-C2 Connectors for the power distribution panel (5) A-C60 Connector for the prelube motor (6) A-C92/F-C1/F-C2/G-C6 Connectors for a RH Control panel (7) C-C22 Primary ECM connector P2 (8) C-C15 Primary ECM connector P1 (9) C-C28 Secondary ECM connector P2 (10) C-C29 Secondary ECM connector P1 (11) C-C47 Connector for the power relay panel (12) C-C17/F-C1/F-C2/G-C6 Connectors for a LH Control panel (13) C-C18/(TB-C1 customer or L-C1/L-C2 EMCP 3) connectors (14) C-C2/J-C1/J-C2 Left hand cross over harness (15) C-C1/E-C1/E-C2 Left hand cross over harness | |
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
- 4
Expected Result:
No diagnostic codes are active at this time.
Results:
- OK - No diagnostic codes are active at this time.
Repair: The problem may be intermittent. If the problem is intermittent refer to Troubleshooting, "Electrical Connectors - Inspect".
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 Battery Voltage on the Signal Wire
- Measure the voltage on the harness side of the sensor connector between terminal C (signal) and engine ground 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 3.
- 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 3. Create a Short at the Sensor Connector
- Disconnect the suspect sensor.
- Use a wire jumper in order to create a short between terminal C (signal) and terminal B (sensor 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.
Expected Result:
A 4 diagnostic code is now active for the suspect sensor.
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. Proceed to Test Step 5.
Test Step 4. Create an Open at the Suspect Sensor Connector
- Remove power from the ECM.
- Disconnect the sensor connector of the suspect sensor 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.
Wait at least 30 seconds in order for the diagnostic codes to become active.
Expected Result:
A 3 diagnostic code is now active for the suspect sensor.
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.
- Check the operation of the ECM by creating an open at the ECM.
- Remove the signal wire for the suspect sensor from the P1 ECM connector. Refer to Illustration 1 for terminal locations.
- Install a jumper wire with Deutsch sockets on each end into the socket for the signal wire of the suspect sensor.
- Reconnect the ECM connectors.
- Restore power to the ECM. Monitor the "Active Diagnostic Code" screen on Cat ET. An open circuit diagnostic code 3 should be active for the suspect sensor.
Wait at least 30 seconds in order for the diagnostic codes to become active.
- Check the operation of the ECM by creating a short at the ECM.
- Install a wire jumper between the wire jumper for the signal wire for the suspect sensor and engine ground.
- Monitor the "Active Diagnostic Code" screen on Cat ET. A 4 diagnostic code should be active when the wire jumper is installed.
Wait at least 30 seconds in order for the diagnostic codes to become active.
- Remove the wire jumper. Reconnect all wires and connectors.
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 connector for the rail.
Repair: If the code is active for the engine oil temperature sensor, make sure that you inspect the connectors that are between the right hand side of the engine and the left hand side of the engine. Repair the wiring and connectors between the ECM and the sensor. Refer to Illustration 1 for terminal locations.
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: Replace the ECM. Refer to Troubleshooting, "ECM - Replace". Verify that the problem is resolved.
STOP