P2771 Code: Meaning, Causes, and Symptoms | OBD2 Codes

P2771 – Four Wheel Drive Low Switch Circuit

 

P2771 Possible Symptoms

 

Engine Light ON (or Service Engine Soon Warning Light)

 

P2771 Possible Causes

 

Faulty Four Wheel Drive Low Switch,Four Wheel Drive Low Switch harness is open or shorted,Four Wheel Drive Low Switch circuit poor electrical connection

 

P2771 Description

 

For vehicles equipped with an active transfer case, the four wheel drive (4WD) low circuit consists of the Powertrain Control Module (PCM) , a transfer case control module and the circuit wiring. The transfer case control module controls the 4WD low signal on the low signal circuit. When the operator selects 4WD low, the transfer case control module grounds the signal circuit, and the 4WD low signal voltage on the circuit changes from ignition voltage to zero volts. The PCM then compensates for transfer case gear reduction in the transmission output shaft speed (OSS) sensor signal. The PCM uses the transmission OSS sensor signal to adjust shift points, line pressure and torque converter clutch (TCC) scheduling. For vehicles not equipped with an active transfer case, the 4WD low circuit consists of the PCM, a transfer case switch and the circuit wiring. The transfer case switch controls the 4WD low signal on the signal circuit. When the operator selects 4WD low, the transfer case switch closes and the 4WD low signal voltage on the signal circuit changes from ignition voltage to zero volts. The PCM then compensates for transfer case gear reduction in the transmission output shaft speed (OSS) sensor signal. The PCM uses the transmission OSS sensor signal to adjust shift points, line pressure and TCC scheduling.