P1148 - FAULT CODE - OBD2

P1148 INFINITI, NISSAN - CLOSED-LOOP CONTROL FUNCTION BANK 1

The Air-Fuel Ratio Sensors have some heating elements through which the sensor temperature is achieved as required for proper operation. This heater is controlled by a dedicated circuit. The pulse modulation is used to regulate the temperature of the sensors accurately. The operation of the sensor depends largely on the temperature. With the information provided by the air-fuel ratio sensors, the air and fuel mixture is regulated and adjusted so that it is the closest to the stoichiometric.

DTC code P1148 OBD2 is a manufacturer-specific code. In brands such as Nissan and Infiniti, this code is set when the Powertrain Control Module (PCM) encounters an air-fuel ratio sensor condition, which prevents the module from entering a closed loop.

• The Check Engine lamp turns on.
• During high temperatures, it is difficult to start the engine.
• Lower fuel efficiency.
• Loss of engine power is observed.
• Unstable idling.
• During acceleration, the engine hesitates.

These are the reasons to set the P1148 OBDII diagnostic code for Nissan and Infiniti:

• Cables or connectors may be in poor condition.
• An air/fuel ratio sensor may be in poor condition.
• The adjustment resistance at the sensor connector may be damaged.
• There may be pollution in the A/F Ratio Sensor from oil or additive based compounds.
• The exhaust could be leaking, very close to the Air/Fuel Ratio Sensor.

Steps to solve the fault code P1148 OBD2:

• Consult the Technical Service Bulletins and record all error codes. If other codes are set, diagnose them in the order shown on the scanner, paying special attention to those related to misfiring, fuel pressure, or ignition system problems.
• After locating the Air/Fuel Ratio Sensor referenced in this code, check all the cables and connectors related to it. If any of these components are commonly damaged, make the necessary repairs.
• Verify the reference voltage, continuity, resistance, and ground signal of the sensor circuit. If the values you get are not within the parameters indicated in the manufacturer's specifications, make repairs.
• Consult the manufacturer's Air/Fuel Ratio Sensor for diagnostic steps. Check that the heater resistance is adequate and if not, replace the sensor.
• Test the tuning resistance, which is built into the connector in most applications. If the reading of this resistance is not within the range determined by the manufacturer, change it.
• Uninstall the A/F Ratio Sensor to verify that it is not damaged or has contamination levels. Make corrections or change the sensor if necessary.