How much does it cost to fix P1148?

DIY repair typically costs $80–$200 for parts. Professional repair runs $200–$500 including parts and labor.

P1148

Powertrain

Moderate

Nissan

Closed Loop Control Function Bank 1

What could P1148 mean for your vehicle?

Add your vehicle to explore possible causes and next checks. AI guidance helps you investigate; it does not confirm a diagnosis.

The P1148 code is specific to Nissan and Infiniti vehicles and indicates that the engine control module (ECM) is unable to enter closed-loop fuel control on Bank 1 (the bank containing cylinder #1). In closed-loop mode, the ECM continuously reads the upstream air/fuel ratio sensor and adjusts the fuel mixture for optimal efficiency and emissions. When this sensor fails or its signal is disrupted, the ECM stays in open-loop mode, running a pre-programmed rich fuel mixture.

You'll likely notice reduced fuel economy, a rough or surging idle, and possible hesitation when accelerating. The exhaust may smell richer than usual. While the vehicle is generally safe to drive short distances, prolonged driving in open-loop mode wastes fuel and can damage the catalytic converter over time.

The most common fix is replacing the upstream air/fuel ratio sensor on Bank 1. Before purchasing a new sensor, inspect the wiring harness and connector for damage or corrosion, and check for exhaust leaks near the sensor location. On V6 Nissan engines, Bank 1 is typically the rear bank closest to the firewall. A quality aftermarket sensor costs $80–$200, while a dealership repair with labor typically runs $200–$500.

Severity

Moderate — Address SoonThis Week

Symptoms

•Check engine light is on
•Rough or fluctuating idle
•Noticeably worse fuel economy
•Hesitation or stumble during acceleration
•Occasional engine surging at steady speed
•Exhaust may smell richer than normal

Likely Causes

Faulty air/fuel ratio sensor (Bank 1 upstream)40%

The upstream A/F ratio sensor on Bank 1 is the most common failure. When it degrades or fails, the ECM cannot enter closed-loop operation and sets this code.

Wiring or connector issue in A/F sensor circuit25%

Damaged, corroded, or shorted wiring between the ECM and the Bank 1 upstream A/F sensor prevents the signal from being read correctly.

Exhaust leak upstream of A/F sensor20%

A significant exhaust leak before the sensor introduces outside air, causing incorrect readings that prevent closed-loop operation.

ECM software or hardware fault15%

In rare cases, the engine control module itself may have a fault in the closed-loop logic or a corrupted calibration, especially after battery disconnects or reflash failures.