Low Engine Coolant Indicator Always On
Low Engine Coolant Indicator Always On
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The engine cooling system contains an engine coolant level switch to alert the driver in the event of a low coolant level. The coolant level switch is mounted at the lowest point in the cooling system surge tank. The low coolant level switch is an electromagnetic device that works in conjunction with a float ring inside the surge tank. The switch is enclosed in a housing molded into the bottom of the surge tank, which isolates it from the coolant in the tank. The float ring is located inside the surge tank and is secured to the switch housing. When the tank is full, the float ring is in close proximity to the sensing element on the switch and the switch circuit closes. If the amount of coolant in the surge tank drops below the level of the switch sensing element, the coolant level switch opens. The coolant level signal circuit is monitored by the instrument panel cluster (IPC). The IPC supplies ignition voltage to the switch on the signal circuit, and a ground is used to complete the circuit. If the IPC detects an open circuit, or a high voltage condition on the signal circuit for greater than 10 seconds, the IPC displays a low coolant level message.
Reference Information
Schematic Reference
Engine Cooling Schematics [1][2]Cooling System
Connector End View Reference
Component Connector End Views Connector End Views By Name
Description and Operation
Cooling System Description and Operation Cooling System
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition OFF, verify the radiator surge tank is filled with engine coolant to the correct level.
• Coolant not at the correct level
Refer to Loss of Coolant Loss of Coolant for further diagnosis.
• Coolant level OK
2. Ignition ON, observe the scan tool Coolant Level Switch parameter. The parameter should display Closed.
• Coolant Level Switch parameter displays Open
Refer to Circuit/System Testing.
• Coolant Level Switch parameter displays Closed
3. All OK.
Circuit/System Testing
Note: Circuit/System Verification must be performed before performing the Circuit/System Testing.
1. Ignition OFF, remove the radiator surge tank fill cap.
2. Verify the coolant level float ring is secured, and is free to move up and down on the coolant level switch housing.
• Float ring not OK
Clean or replace the radiator surge tank.
• Float ring OK
3. Ignition OFF, disconnect the harness connector at the B33 coolant level switch.
4. Test for less than 5 ohm between the ground circuit terminal 1 and ground.
• If 5 ohm or greater
Test the ground circuit for an open/high resistance.
• If less than 5 ohm
5. Install a 3 A fused jumper wire between the signal circuit terminal 2 and the ground circuit terminal 1.
6. Ignition ON, verify the scan tool Coolant Level Switch parameter displays Closed.
• Coolant Level Switch parameter displays Open
1. Ignition OFF, disconnect the P16 IPC connector.
2. Test the coolant level signal circuit for less than 2 ohm between IPC terminal 9 and B33 terminal 2.
• If 2 ohm or greater, repair the open/high resistance in the circuit.
• If less than 2 ohm
3. Ignition ON, test for less that 1 V between the B33 signal circuit terminal 2 and ground.
• If 1 V or greater, repair the short to voltage on the signal circuit.
• If less than 1 V, replace the P16 IPC.
• Coolant Level Switch parameter displays Closed
7. Replace the B33 coolant level switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Radiator Surge Tank Replacement (LF1,LFW, or LFX) Radiator Surge Tank Replacement
* Engine Coolant Level Indicator Module Replacement Service and Repair
* Control Module References Control Module References for ECM replacement, setup, and programming