P1278 Air Fuel Ratio Sensor 1 Circuit Slow Response

Possible causes
– Air fuel ratio (A/F) Harness or connectors is open or shorted
– Air fuel ratio (A/F) sensor 1 Bank 1
– Air fuel ratio (A/F) sensor 1 heater Bank 1
– Fuel pressure
– Fuel injector
– Intake air leaks
– Exhaust Gas leaks
– PVC
– Air Flow Meter
When is the code detected?
The response (from RICH to LEAN) of the A/F signal computed by ECM from A/F sensor 1 signal takes more than the specified time.
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
– Possible rough engine idle
P1278 Description
The Air Fuel Ratio (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