GEAR 1252951 - Caterpillar

System Operation Description:Use this procedure under the following situation:Use this procedure if any of the following diagnostic codes are active or easily repeatable:
111-02 Coolant Level signal invalid (12)
111-03 Coolant Level voltage high (12)
111-04 Coolant Level voltage low (12)Do not use this procedure for either of the following diagnostic codes:
111-01 Low Coolant Level Warning (62)
111-11 Very Low Coolant Level (62)
111-14 Low Coolant Level WarningThese diagnostic codes indicate a low coolant level but not an electrical system malfunction. Refer to Troubleshooting, "111-01 Low Coolant Level Warning", Troubleshooting, "111-11 Very Low Coolant Level" or Troubleshooting, "111-14 Low Coolant Level Warning" for the proper troubleshooting procedure.The following background information is related to this procedure: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".4-Pin SensorThe sensor indicates the presence or the absence of coolant at the sensor probe. A sensor with a 4-pin connector that requires a +5 VDC connection to a power supply must be used. The sensor is powered from the ECM through the ECM vehicle harness connector J1/P1 terminal 2 (+5 VDC). The ECM vehicle harness connector has 70 terminals. The signal wires for the coolant level sensor are connected at J1/P1-54 (coolant level low) and at J1/P1-49 (coolant level normal). The common wire for the sensor is connected to the J1/P1 ECM connector through terminal 5 (AP sensor/switch common).Note: If both parameters are set and a sensor is not installed, 111-02 diagnostic code will be logged.
Table 1
ECM Output for the 4-Pin Sensor
Pin location Engine coolant level normal Engine coolant level low
J1-49 5 VDC 0 VDC
J1-54 0 VDC 5 VDC 2-Wire Float SensorTo use a 2-wire float sensor, the parameter "Coolant Level Sensor" must be programmed to "2-wire float sensor". The sensor is connected to P1/J1-26 (sensor input) and to P1/J1-5 (AP sensor/switch common). The sensor will provide information to the ECM at P1/J1-26 that will enable the ECM to determine if the coolant level is normal,