Code Definition

P1148 — Closed Loop right hand bank 1

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Infiniti

About P1148

P1148 is a manufacturer-specific powertrain diagnostic trouble code recorded for Infiniti vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1148 is stored, the module has detected a bank-specific fault, meaning it applies only to one cylinder bank of a multi-bank engine.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1148 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

Closed loop control is the mode in which the Engine Control Module (ECM) uses the front oxygen or air fuel ratio sensor feedback to continuously trim the fuel mixture on a bank. DTC P1148 sets when the ECM is unable to achieve or maintain closed loop fuel control on bank 1, the bank containing cylinder number one, which on this engine is the right hand bank. The usual reason is that the front oxygen or air fuel ratio sensor signal is not swinging correctly, so the ECM cannot trust it for feedback and stays in open loop. Symptoms include poor fuel economy, increased emissions, possible rough ru...

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