BOLT 1D4631 - Caterpillar

3126B (7AS),
C-10 (3CS),
C-12 (2KS),
3406E (1MM, 2WS) Truck EnginesOEM truck manufacturers experienced a shortage of 4-pin coolant level sensors from January 31, 1999 to late February 1999. OEM's use these sensors in order to measure the coolant level in the radiator of the vehicle. The OEM's have approved two methods to overcome the shortage of coolant level sensors until coolant level sensors can be installed in the field.
The first method used by the OEM's is to program the Coolant Level Sensor parameter to "OFF" and terminate the harness connector with a sealed plug. The vehicles can then be reprogrammed at a later date when the sensor is installed.
Other truck manufacturers have elected to use a short circuit plug that not only seals the connection, but provides a connection between pins A and B and pins C and D. As a result the ECM will display the Coolant Level Status as "OK". However, should the plug become disconnected or an open circuit occur, a 111-02 Coolant Level Sensor Fault will become active. This can affect engine operation if the Engine Monitoring is programmed to Derate or Shutdown. The coolant level sensor will be installed, and the plug removed at a later date. The ECM will not require reprogramming.
All truck manufacturers have placed a warning sticker on the vehicle to inform the operator that the coolant level sensor is not functioning.
When working on a vehicle manufactured between January 1, 1999 and February 28, 1999 that has an active 111-02 Coolant Level Sensor Fault and does not have a coolant level sensor installed, be sure to check the wiring and connector plug for an open circuit.