The low pressure sensor is what will indicate a low condition, or a fault in that circuit. Here is the schematic and info for a 1349 code, 1348 is similar.
DTC B1347 Very Low A/C Refrigerant Warning
In the process of controlling the compressor clutch, the heater and A/C programmer monitors certain inputs for an indication of a low refrigerant charge. If the system refrigerant state of charge falls below approximately 1/4 capacity, the heater and A/C programmer is capable of detecting this condition. The programmer will display VERY LOW REFRIGERANT--A/C COMPRESSOR OFF on the driver information center (DIC) in order to warn the operator.
The heater and A/C programmer determines the state of the charge by monitoring the temperature change in the low temperature sensor during the compressor engagement. This temperature drop is referenced by the heater and A/C programmer as a function of the ambient air temperature. If the refrigerant charge is too low, the refrigerant boils instantaneously after passing through the orifice tube. This action creates a large rapid change in the low temperature sensor reading. After several incidents are counted, the heater and A/C programmer sets DTC B1347. The message VERY LOW REFRIGERANT--A/C COMPRESSOR OFF will be displayed on the DIC. If a DTC B1347 is set, the compressor clutch disengages and remains disengaged until DTC B1347 is cleared. DTC B1347 may repeat if excessive pressure exists in the A/C charging station tank. Repair the A/C charging station before properly diagnosing DTC B1347.
The low side refrigerant temperature drops too quickly during several of the compressor cycles.
Action Taken When the DTC Sets
" The system disables the A/C compressor until the DTC is cleared.
" The system displays the VERY LOW REFRIGERANT--A/C COMPRESSOR OFF message on the DIC.
Check for 12 volts at the pink wire pin A, check for 12 volts out of the sensor at pin B, and at the terminal at the programmer. If you lose 12 volts on the programmer side, you are losing it to open switch or pressure below 10 psi. The programmer is under the RH side of the instrument panel.
Friday, July 16th, 2010 AT 4:40 PM