U121B Engine Code Repair

Meaning of U121B engine trouble code is a kind of network trouble code and theoretically you can drive for a few weeks or even months with a broken MAF sensor. You will notice a decrease in gas mileage and over time the car will eventually start stalling a lot. At a shop, the replacement cost is between $240-$400 depending on the car, but that's usually the cost of parts because the labor is relatively simple.

U121B Fault Symptoms :

U121B Possible Solution:

Air Conditioning Pressure Sensor (ACP) Insufficient Pressure Change Each time the A/C clutch engages, the PCM is looking for a pressure change in the refrigerant. If the change in pressure is outside of the calibration the DTC will set. A/C system mechanical failure Open ACP or VREF circuit A/C sensor damaged A/C system electrical failure A/C clutch always engaged Verify A/C system function, including refrigerant charge.

U121B Code Meaning :

Regarding the U121B code, it would probably be worthwhile to carefully inspect the wire harness near the intake manifold bracket. This is done most easily from below the car in the area near the oil filter.

U121B DTC reports a sensor fault, replacement of the sensor is unlikely to resolve the underlying problem. The fault is most likely to be caused by the systems that the sensor is monitoring, but might even be caused by the wiring to the sensor itself.