Engine Coolant Level Switch/Sensor Diagnosis

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Schematic:

CIRCUIT DESCRIPTION
The engine coolant level switch is located in the radiator surge tank. The engine coolant level switch is a float type switch. The Powertrain Control Module (PCM) supplies a voltage to the engine coolant level switch. The engine coolant level switch is a normally open switch. When the coolant level is within an acceptable range the engine coolant level switch closes. The switch opens when the engine coolant level drops below a predetermined amount. When the PCM detects a high signal voltage, switch open, from the engine coolant level switch the PCM sends a Class 2 message to the Instrument Panel Cluster (IPC). The IPC displays the LOW COOLANT message.

DIAGNOSTIC AIDS

IMPORTANT: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

^ The following may cause an intermittent:
- Poor connections-Check for adequate terminal tension. Refer to Testing for Intermittent and Poor Connections in Diagrams.
- Corrosion
- Mis-routed harness
- Rubbed through wire insulation
- Broken wire inside the insulation
- A float that is stuck
^ For an intermittent, refer to Symptoms. Symptom Related Diagnostic Procedures

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
4. This steps tests the engine coolant level sensor signal circuit between the PCM and the sensor.
6. This steps tests the engine coolant level sensor ground circuit between the PCM and the sensor.
9. This steps tests the engine coolant level sensor signal circuit for a short to ground.
10. This steps tests for an open in the engine coolant level sensor signal circuit between the PCM and the engine coolant level sensor.