Possible causes

– Faulty heated oxygen (O2) sensor 2 (rear)
– Intake air leaks
– Heated oxygen (O2) sensor 2 (rear) harness is open or shorted
– Heated oxygen (O2) sensor 2 (rear) circuit poor electrical connection
– Inappropriate fuel pressure
– Faulty fuel injectors

Tech notes

Replacing the rear O2 Sensor usually takes care of the problem

When is the code detected?

The P1147 code is triggered when the maximum voltage from the sensor is not reached to the specified voltage.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Possible high fuel consumption
– Possible excessive smoke from exhaust

P1147 2004 NISSAN SENTRA Description

The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.