Low Engine Coolant Level Indicator Diagnosis

Circuit Description
This test checks for a low engine coolant condition. The pressurized coolant bottle is equipped with a level switch which opens when coolant level is low. The PCM monitors the state of this switch through CKT 1478 and measures the time that the switch is open. If the switch is open for longer than a calculated period of time, the PCM signals the Instrument Panel Cluster (IPC)/Driver Information Center (DIC) via the data link to turn on the LOW ENGINE COOLANT message.

The calculated period of time, between 2.1 and 26.3 seconds, before a low coolant condition is recognized is based on vehicle speed and acceleration. The higher vehicle speed and acceleration, the longer the time before a low coolant condition will be recognized. Low coolant level message is displayed on the IPC/DIC for the entire ignition cycle.

Diagnostic Aids
The Engine coolant level switch shares a common sensor/switch ground (CKT 451). An intermittent at any of these connections could possibly cause the Low Engine coolant message to remain ON If coolant level is OK.
If the customer complaint is that the coolant level is low but the message does not display, check the engine coolant level switch for binding or stuck closed.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
2. Checks if low coolant level is causing the message.
4. Checks for a faulty coolant level switch.
5. Checks CKT 451 for an open.
6. This test checks for a short or open in CKT 1478 or a faulty PCM.