Chart C-16 Low Coolant Level Switch

Chart C-16:

Low Coolant Switch Circuit:

CIRCUIT DESCRIPTION
This test checks for a low engine coolant coolant condition. The pressurized coolant bottle is equipped with a level switch which opens when coolant level is low. The Powertrain Control Module (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/Driver Information Center (IPC/DIC) via the data link to turn on the "LOW COOLANT LEVEL" 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.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Checks if low coolant level is causing the message.
2. Checks for a faulty coolant level switch.
3. Checks CKT 251 for an open.
4. This test checks for a short or open in CKT 1478 or a faulty PCM.

DIAGNOSTIC AIDS
The low coolant level switch shares a common sensor/switch ground (CKT 251). An intermittent at any of these connections could possible cause the low coolant level switch light to remain "ON." If coolant level is OK.