P2771 Possible Causes
- Faulty four-wheel drive low switch
- Four-wheel drive low switch harness is open or shorted
- Poor electrical connection in four-wheel drive switch circuit
How to Fix Code P2771
Check the “Possible Causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
Possible Symptoms
Check engine light on (or service engine soon warning light)
P2771 Meaning
For vehicles equipped with an active transfer case, the four-wheel drive low (4WD) circuit consists of the powertrain control module (PCM), a transfer case control module, and circuit wiring. The transfer case control module controls the 4WD low signal on the 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 the transfer case reduction ratio 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) programming.
For vehicles not equipped with an active transfer case, the four-wheel drive low circuit consists of the PCM, a transfer case switch, and 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 the transfer case reduction ratio 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 programming.