CAT 3126B Fault Code: 111-04 PID: Flash Code 12 SPN: 111 FMI: 4 Coolant Level voltage low

Conditions Which Generate This Code:

This condition occurs when there is a short in the circuit for the “2-wire float sensor”. The “Coolant Level Sensor” parameter must be programmed to “2-wire float sensor” before this diagnostic code can occur. If the “Coolant Level Sensor” parameter is programmed to “2-pin switch”, or “4-pin” this diagnostic code is disabled.

The coolant level sensor is installed by the vehicle’s Original Equipment Manufacturer (OEM). This sensor is an optional sensor for “Engine Monitoring”. Engine monitoring is a programmable feature of the Caterpillar Engine Control Module (ECM). The sensor is selectable through a customer programmable parameter and the customer programmable parameter may be protected by customer passwords. Some OEM installed coolant level sensors are not connected to the ECM. Do not confuse an OEM installed coolant level sensor that is independent of engine monitoring with the coolant level sensor that is used for engine monitoring.

The customer programmable parameter for the coolant level sensor can be programmed to “4-Pin”, “2-wire float sensor”, or “2-pin switch”. Also, the customer programmable parameter for the coolant level sensor can be programmed to “NO” if the option for the coolant level sensor is not being used.

If the parameter “Coolant Level Sensor” is programmed to “NO”, the coolant level sensor is ignored by the ECM. Conversely, if the parameter is set, then a sensor must be installed. The coolant level is monitored by the engine monitoring system when the parameter “Coolant Level Sensor” is programmed to “4-Pin” or “2-wire float sensor”.

Probable Causes:

1) Coolant level sensor
2) Coolant level sensor harness/connector
3) ECM Connection
4) Wiring between ECM and coolant level sensor
5) ECM Failure