The Engine Control Module (ECM) monitors a coolant level sensor in order to determine the coolant level. The coolant level sensor is installed by the vehicle manufacturer. The coolant level sensor is one of the following types:
- 4-Pin Sensor
- 2 Wire Float
- 2-Pin Switch
The "Coolant Level Sensor" parameter must be programmed to match the type of sensor in order for the monitoring system to function correctly. The following tables describe each sensor.
| Operation of the 4-Pin Sensor
This sensor has two output terminals. The voltage on the terminals indicates the coolant level. |
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| Condition | Code | Terminal on the P1 Connector | ||||
| Suspect Parameter Number (SPN) | Failure Mode Identifier (FMI) | Code Description | Output Terminal on the 4-Pin Sensor | Voltage on the Terminal | ||
| Normal Coolant Level | N/A | D | Minimum of 4.1 VDC | P1-49 | ||
| A | Maximum of 0.5 VDC | P1-54 | ||||
| Low Coolant Level | 111 | 17 | Engine Coolant Level : Low - Least Severe (1) | D | Maximum of 0.5 VDC | P1-49 |
| A | Minimum of 4.1 VDC | P1-54 | ||||
| Very Low Coolant Level | 111 | 1 | Engine Coolant Level : Low - Most Severe (3) | This code is activated after the "low coolant level" condition has existed for a few seconds. | ||
| 111 | 2 | Engine Coolant Level : Erratic, Intermittent, or Incorrect | This code is activated if both outputs are the same voltage for at least two seconds. | |||
| Operation of the 2-Wire Float Sensor (1)
This sensor has one output terminal. The voltage on the terminal indicates the coolant level. |
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| Condition | Code | Voltage Range (2) | Terminal on the P1 Connector | |||
| Suspect Parameter Number (SPN) | Failure Mode Identifier (FMI) | Code Description | ||||
| Normal Coolant Level | N/A | 0.8 VDC
to 1.8 VDC |
P1-26 | |||
| Low Coolant Level | 111 | 17 | Engine Coolant Level : Low - Least Severe (1) | 2.0 VDC
to 3.0 VDC |
||
| Very Low Coolant Level | 111 | 1 | Engine Coolant Level : Low - Most Severe (3) | 3.3 VDC
to 4.3 VDC |
||
| 111 | 3 | Engine Coolant Level : Voltage Above Normal | Voltage is greater than 4.5 VDC. | |||
| 111 | 4 | Engine Coolant Level : Voltage Below Normal | Voltage is less than 0.5 VDC. | |||
| (1) | There are two types of sensor that can be utilized when the ECM is programmed to this option. Some sensors will have 2 wires and some sensors will have 3 wires. A sensor with 3 wires requires 5 VDC in order to operate. The power wire for this sensor may be connected to terminal 2 of the P1 connector. The 2-wire float sensor does not require electrical power in order to operate. |
| (2) | The voltage that is between the ranges is a hysteresis band. The hysteresis band will prevent false indications when the coolant sloshes in the tank. |
| Operation of the 2-Pin Switch
This switch creates a short circuit when coolant is present. |
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| Condition | Code | Condition of the Circuit | ||||
| Suspect Parameter Number (SPN) | Failure Mode Identifier (FMI) | Code Description | ||||
| Normal Coolant Level | N/A | Short circuit between P1-49 and sensor common | ||||
| Low Coolant Level | 111 | 17 | Engine Coolant Level : Low - Least Severe (1) | Open circuit between P1-49 and sensor common | ||
| Very Low Coolant Level | 111 | 1 | Engine Coolant Level : Low - Most Severe (3) | This code is activated after the "low coolant level" condition has existed for a few seconds. | ||
Test Step 1. Use Caterpillar Electronic Technician (ET) to Check for an Active Coolant Level Sensor Fault
- Establish communication between Cat ET and the engine ECM. Refer to Troubleshooting, "Electronic Service Tools", if necessary.
- Access the active diagnostic screen on Cat ET.
- Verify that a diagnostic code that is related to the coolant level switch is active.
Expected Result:
There is an active code for the coolant level sensor.
Results:
- Active 111-2 code - There is a problem with the circuit for the 4-pin sensor. Proceed to Test Step 2.
- Active 111-3 or 111-4 code - There is a problem with the circuit for the 2-wire float sensor. Proceed to Test Step 8.
Test Step 2. Inspect Electrical Connectors and Wiring for the 4-Pin Sensor
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| Illustration 1 | g01118000 |
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This is a typical schematic for the 4-pin sensor. The return wire may be connected to P1-3, P1-5, or P1-18. | |
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| Illustration 2 | g01153498 |
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Pin locations on ECM connector (P1-2) +5V supply (P1-5) AP sensor/switch common (P1-49) Coolant level normal (P1-54) Coolant level low | |
- Thoroughly inspect J1/P1 ECM connector, the connector for the extension harness for the coolant level and the terminals for the coolant level sensor in the connectors. The connector for the extension harness for the coolant level connects the coolant level sensor to the vehicle harness in the engine compartment of some chassis. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
- Refer to Illustration 2. Perform a
45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the following connections:- P1-2 +5V supply
- P1-5 AP sensor/switch common
- P1-49 Coolant level normal
- P1-54 Coolant level low
- Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
- Check the harness and wiring for abrasion and for pinch points from the sensor to the ECM.
Expected Result:
All connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.
Results:
- OK - Proceed to Test Step 3.
- Not OK -
Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.
Verify that the repair eliminates the problem. Clear all diagnostic codes.
STOP
Test Step 3. Disconnect the Coolant Level Sensor and Check the Supply Voltage (+5 VDC)
- Turn the keyswitch to the OFF position.
- Disconnect the coolant level sensor from the harness.
- Use a multimeter to measure the voltage at the harness connector from terminal C (+ 5 VDC) to terminal B (AP sensor/switch common).
- Turn the keyswitch to the ON position.
Expected Result:
The measured voltage is 5.0 ± 0.2 VDC.
Results:
- OK - Proceed to Test Step 4.
- Not OK - Proceed to Test Step 5.
Test Step 4. Disconnect the Coolant Level Sensor and Check the Coolant Level Harness
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| Illustration 3 | g00651005 |
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Jumper wire | |
- Turn the keyswitch to the OFF position.
- Disconnect the coolant level sensor from the harness.
- Use a jumper wire in order to connect terminal D (coolant level normal) to terminal B (AP sensor/switch common) at the harness connector.
Refer to Illustration 3.
- Turn the keyswitch to the ON position.
- While the jumper wire is in place, access the status screen that indicates the coolant level status.
- Wait for 30 seconds. Read the status and record the status.
Expected Result:
The coolant level status indicates "LOW" with the jumper in place.
Results:
- OK - Leave the jumper wire in place. If a breakout T is installed, leave the breakout T in place also. Proceed to Test Step 6.
- Not OK - Proceed to Test Step 7.
Test Step 5. Disconnect the Terminal for the Sensor Supply (+5 VDC) from the ECM Connector
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| Illustration 4 | g01118013 |
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Breakout T (2) +5V supply (5) AP sensor/switch common | |
- Turn the keyswitch to the OFF position.
- Disconnect the J1/P1 ECM connector.
- Install a breakout T between the J1 and the P1 ECM connector.
- Turn the keyswitch to the ON position.
- Measure the voltage at the breakout T from terminal 2 to terminal 5.
Refer to Illustration 4.
Expected Result:
The measured voltage is 5.0 ± 0.2 VDC.
Results:
- OK - The measured voltage is 5.0 ± 0.2 VDC. The problem is located in the harness wiring.
Repair: Repair the wiring or replace the wiring, as required.
Verify that the repair eliminates the problem.
STOP
- Not OK - The problem is on the ECM side.
Repair: Temporarily connect a test ECM. Ensure that the "Coolant Level Sensor" is programmed to match the old ECM. Check the test ECM by measuring the voltage at the breakout T from terminal 2 to terminal 5 again. If the problem is resolved with the test ECM, reconnect the suspect ECM. If the problem returns with the suspect ECM, replace the ECM.
STOP
Test Step 6. Check the Wire Harness for the Coolant Level Low
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| Illustration 5 | g00651008 |
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Jumper wires | |
- Turn the keyswitch to the OFF position.
- Use two jumper wires to connect terminal A (coolant level low) and terminal D (coolant level normal) to terminal B (sensor common) at the harness connector.
Refer to Illustration 5.
- Turn the keyswitch to the ON position.
- While the jumper wires are in place, access the active diagnostic code screen on Cat ET.
- Verify that 111-2 diagnostic code is active.
Note: Wait for 30 seconds for the activation of the diagnostic code.
Expected Result:
The 111-2 diagnostic code is active while the jumper wires are in place.
Results:
- OK - The 111-2 diagnostic code is active while the jumper wires are in place. The harness and the ECM are working correctly.
Repair: Remove the jumpers. Replace the sensor and ensure that 111-2 diagnostic code disappears with the new sensor.
Verify that the repair eliminates the problem. Clear all diagnostic codes.
STOP
- Not OK - The 111-2 diagnostic code is not active while the jumper wires are in place. Proceed to Test Step 7.
Test Step 7. Check the ECM
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| Illustration 6 | g01118015 |
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Breakout T (5) AP sensor/switch common (18) Input sensor common 1 (49) Coolant level normal (54) Coolant level low | |
- Turn the keyswitch to the OFF position.
- Fabricate two jumper wires
100 mm (4 inch) long. Crimp a Deutsch pin to both ends of each wire. - Turn the keyswitch to the ON position.
- Observe the coolant level sensor status on Cat ET. Install the jumper into the breakout T in order to connect terminal 49 (coolant level normal) to terminal 5 (AP sensor/switch common).
- Monitor the coolant level sensor status while the jumper is being inserted and removed. Wait for 30 seconds between the insertion of the jumper and the removal of the jumper. Waiting for 30 seconds allows the ECM to acknowledge the change. While the jumper remains in place, a diagnostic code for low coolant level should be active.
- Record the result.
- Leave the jumper installed in the breakout T.
- Install a jumper wire from 54 coolant level low to 18 input sensor common 1 of the breakout T.
- While both jumper wires are in place, access the active diagnostic code screen. Verify that a 111-2 diagnostic code is active.
Wait for 30 seconds for the activation of the diagnostic code.
Refer to Illustration 6.
Expected Result:
The coolant level sensor status behaves in the following manner:
- The Coolant Level Sensor Status indicates "OK" before the jumper wire is installed between terminal 49 and terminal 5. 111-2 diagnostic code may be active.
- The coolant level sensor status changes to "LOW" after the jumper wire is installed between terminal 49 and terminal 5. Also, a diagnostic code for low coolant level becomes active.
The 111-2 diagnostic code is active when both jumper wires are installed.
Results:
- OK - The 111-2 diagnostic code is active when both jumper wires are installed. The ECM is functioning properly.
Repair: Repair the harness or replace the harness, as required.
Verify that the repair eliminates the problem. Clear all diagnostic codes.
STOP
- Not OK - The 111-2 diagnostic code is not active when both jumper wires are installed. There may be a problem with the ECM.
Repair: Temporarily connect a test ECM. Ensure that the "Coolant Level Sensor" is programmed to match the old ECM. If the problem is resolved with the test ECM, reconnect the suspect ECM. If the problem returns with the suspect ECM, replace the ECM.
STOP
Test Step 8. Inspect Electrical Connectors and Wiring for the 2-Wire Float Sensor
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| Illustration 7 | g00882602 |
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This is a typical schematic for the 2-wire float sensor. The return wire may be connected to P1-3, P1-5, or P1-18. | |
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| Illustration 8 | g01153501 |
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Pin locations on ECM connector (P1-5) AP sensor/switch common (P1-26) Coolant level input | |
- Thoroughly inspect the J1/P1 ECM connector, the connector for the coolant level sensor and the terminals for the coolant level sensor in the connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
- Perform a
45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the following connections:- P1-26 coolant level input
- P1-5 AP sensor/switch common
Refer to Illustration 8.
- Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
- Check the harness and wiring for abrasion and for pinch points from the sensor to the ECM.
Expected Result:
All connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.
Results:
- OK - The wiring appears to be OK. Proceed to Test Step 9.
- Not OK - There is a problem with the wiring.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.
Verify that the repair eliminates the problem. Clear all diagnostic codes.
STOP
Test Step 9. Disconnect the Coolant Level Sensor and Check the Supply Voltage (+5 VDC)
- Turn the keyswitch to the OFF position.
- Disconnect the coolant level sensor from the harness.
- Use a multimeter to measure the voltage at the harness connector.
- Turn the keyswitch to the ON position.
Expected Result:
The measured voltage is 5.0 ± 0.2 VDC.
Results:
- OK - The correct voltage is reaching the sensor.
Repair: Replace the sensor.
STOP
- Not OK - The correct voltage is not reaching the sensor. Proceed to Test Step 10.
Test Step 10. Disconnect the Terminal for the Sensor Supply (+5 VDC) From the ECM Connector
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| Illustration 9 | g01118029 |
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Breakout T (5) AP sensor/switch common (26) Coolant level input | |
- Turn the keyswitch to the OFF position.
- Disconnect the J1/P1 ECM connector.
- Install a breakout T between the J1 and P1 ECM connector.
- Turn the keyswitch to the ON position.
- Measure the voltage at the breakout T from terminal 26 to terminal 5.
Refer to Illustration 9.
Expected Result:
The measured voltage is 5.0 ± 0.2 VDC.
Results:
- OK - The problem is located in the harness wiring.
Repair: Repair the wiring or replace the wiring, as required.
Verify that the repair eliminates the problem.
STOP
- Not OK - The problem is on the ECM side.
Repair: Temporarily connect a test ECM. Ensure that the "Coolant Level Sensor" is programmed to match the old ECM. Check the test ECM by measuring the voltage at the breakout T from terminal 26 to terminal 5 again. If the problem is resolved with the test ECM, reconnect the suspect ECM. If the problem returns with the suspect ECM, replace the ECM.
STOP