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P1148 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

P1148 is an OBD-II Code that refers to Closed Loop Control Function Bank 1 

Meaning

A P1148 code is a manufacturer specific diagnostic trouble code related to Infiniti and Nissan vehicles and similar makes that occurs when the ECM/PCM detects a problem with the closed loop control function of the Bank 1 A/F sensor. The temperature of the sensor is critical to its performance. The air and fuel mixture is regulated and adjusted, with the assistance of the air-fuel ratio sensors, to be as close to stoichiometric as feasible.

If the ECM detects a problem with the closed loop system, it will set a P1148.

Causes

Common causes for this code include:

  • Faulty cables or harness
  • Bad air/fuel ratio sensor
  • Sensor connector may be damaged.
  • Contaminated A/F Ratio Sensor
  • Exhaust leak near the Air/Fuel Ratio Sensor

Symptoms

The symptoms of a P1148 code are:

  • Illuminated Check Engine Light
  • Rough idle or fluctuations
  • Bad fuel economy
  • Power loss
  • Engine may stumble or hesitate upon acceleration
  • Hard, or impossible to start the engine when it is hot

Diagnosis

To diagnose a P1148 DTC code, a technician would:

  1. Scan for codes in the ECM and look at the freeze frame data for failure.
  2. Visually inspect all the wiring and connectors in the circuit.
  3. Check sensor output with a scan tool
  4. Check for exhaust leaks
  5. Test the air/fuel ratio sensor according to manufacturer’s specifications

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P1148 code:

  • Not thoroughly inspecting all the wiring and connectors for damage.
  • Not testing the sensor according to manufacturer’s specifications.
  • Failing to check for exhaust leaks.

How serious is this?

A P1148 code is a fairly serious code that can lead to drivability issues and may cause engine damage if not addressed in a timely manner.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Broken or faulty wirings must be repaired or replaced
  • Bad or damaged connectors must be replaced
  • A/F ratio sensor may need to be replaced
  • Exhaust leaks must be repaired

Related codes

A P1148 is related to and may be accompanied by the following codes:

P1130 – Air-Fuel Ratio Sensor (Bank 1) Circuit Lean

P1153 – Air-Fuel Ratio Sensor (Bank 2) Circuit Lean

P0137 – Oxygen Sensor (Bank 1 – Sensor 2) Low Voltage Input

P0138 – Oxygen Sensor (Bank 1 – Sensor 2) High Voltage Input

Conclusion

In conclusion, the P1148 code is a diagnostic trouble code that refers to a problem with the closed loop control function of the Bank 1 A/F sensor. The most common causes are faulty cables or harnesses, a bad air/fuel ratio sensor, or contaminated A/F Ratio Sensor. The symptoms of this code include an illuminated Check Engine Light, rough idle or fluctuations, bad fuel economy, power loss, and engine may stumble or hesitate upon acceleration.