COUPLER AS 1221802 - Caterpillar

Use this procedure to troubleshoot a problem with the coolant level sensor.The coolant level sensor monitors the engine coolant level in order to warn the operator when the coolant level is low.When the probe is not immersed in coolant, approximately +8 VDC is sourced to the sensor signal wire. When this condition is detected by the Electronic Control Module (ECM), an event code is activated.Prior to troubleshooting any problems with the coolant level sensor, use Cat® Electronic Technician (ET) to check the installation status for the sensor. The coolant level sensor configuration parameter must be set to "Installed" in order for the ECM to monitor the signal from the sensor.The activation of an event code and/or a warning lamp is probably caused by a low coolant level. The next likely cause is a problem with the wiring harness, a connector, or the sensor.
Illustration 1 g03880983
Table 1
Troubleshooting Test Steps Values Results
1. Check the Coolant Level
Allow the engine to cool prior to removal of the cooling system pressure cap.
A. Remove electrical power from the Electronic Control Module (ECM).
B. Check the coolant level. Refer to the Operation and Maintenance Manual for the proper procedure to check the coolant level.
Coolant Level
Result: The coolant is at the proper level.
Proceed to Test Step 2.
Result: The coolant level is low.
Repair: Add coolant according to the procedure in the Operation and Maintenance Manual.
There may be a leak in the cooling system. Identify the source of the coolant leak. Repair the leak. Refer to Systems Operation/Testing and Adjusting, "Cooling System" for additional information.
If the problem is not resolved, proceed to Test Step 2.
2. Check the Supply Voltage at the Sensor Connector
A. Disconnect the coolant level sensor at the sensor connector.
B. Restore electrical power to the ECM.
C. Measure the voltage between the following wiring harness connector terminals for the coolant level sensor:
- Terminal A (sensor supply) and Terminal B (sensor return)
D. Remove electrical power from the ECM.
8.0 0.5 VDC
Result: The voltage measurement is 8.0 0.5 VDC. The supply voltage is reaching the sensor.
Proceed to Test Step 3.
Result: The voltage measurement is not 8.0 0.5 VDC.
Repair: The sensor supply voltage is not reaching the sensor. There is a problem in the circuit for the sensor supply. Repair the wiring harness between the sensor and the ECM.
If the problem is not resolved, proceed to Test Step 3.
3. Short the Signal Wire to Ground on the Affected Sensor and Monitor the Status for "Coolant Level"
A. Fabricate a jumper wire that is long enough to create a short circuit between two terminals at the affected coolant level sensor harness connector. Crimp connector pins to each end of the jumper wire.
B. Install the jumper wire between the following wiring harness connector terminals for the affected coolant level sensor:
- Terminal B (sensor return) and Terminal C (sensor signal)
C. Connect Cat ET.
D. Use Cat ET to monitor the status of the "Coolant Level".
Note: If the coolant level is in above the full sensor, the status will be set to "FULL".
If the coolant level