CAT 3406E (Prefix 5DS or 1LW) Fault Code: 12 PID: 111 SPN: FMI: 2 Coolant Level signal invalid

The ECM detects the following conditions:

•The coolant level sensor is sending an invalid signal for more than ten seconds.
•The “Coolant Level Sensor” parameter is programmed to “Yes”.

Probable Causes:

1) ECM Connection/Harness
2) Coolant sensor failure
3) Coolant sensor harness failure
4) ECM Failure