Possible causes

Harness or connectors (The A/F sensor 1 circuit is open or shorted.)

Air fuel ratio (A/F) sensor 1

When is the code detected?

The A/F signal computed by ECM from the A/F sensor 1 (Bank 1) signal is constantly approx. 0V.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P1271 Description

The A/F sensor is a planar dual-cell limit current sensor. The sensor element of the A/F sensor is the combination of a Nernst concentration cell (sensor cell) with an oxygen-pump cell, which transports ions. It has a heater in the element.

The sensor is capable of precise measurement λ= 1, but also in the lean and rich range. Together with its control electronics, the sensor outputs a clear, continuous signal throughout a wide λ range (0.7 < λ < air).

The exhaust gas components diffuse through the diffusion gap at the electrode of the oxygen pump and Nernst concentration cell, where they are brought to thermodynamic balance.

An electronic circuit controls the pump current through the oxygen-pump cell so that the composition of the exhaust gas in the diffusion gap remains constant at λ = 1. Therefore, the A/F sensor is able to indicate air/fuel ratio by this pumping of current. In addition, a heater is integrated in the sensor to ensure the required operating temperature of 700 – 800C (1,292 – 1,472F).

P1271 Information for specific makes

P1271 BUICK
P1271 CADILLAC
P1271 CHEVROLET
P1271 DODGE
P1271 FORD
P1271 GMC
P1271 NISSAN
P1271 INFINITI