Engine-Codes - Generic - P1151

P1151 - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2

Repair Importance Level: 3/3
Repair Difficulty Level: 2/3  What is this?
Table of contents

P1151 Possible Causes

  • Faulty Upstream Oxygen Sensor Bank 2
  • Fuel pressure high or low
  • MAF sensor dirty/defective
  • Vacuum leak on engine
  • Leaking fuel injector or fuel pressure regulator
  • Faulty Powertrain Control Module (PCM)

How is the P1151 code repair?

Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.

Tech Notes

The code means that the Powertrain Control Module (PCM) has detected a lean system, which means that there is either not enough fuel or and excessive amount of air in the system. Start by checking for vacuum leaks.

What is the cost to diagnose the P1151 code

Labor: 1.0

The cost to diagnose the P1151 code is 1.0 hour of labor. The auto repair labor rates vary widely across the country, and even within the same city. Most auto repairs shops charge between $75 and $150 per hour.

Possible Symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

P1151 Meaning

The Heated Oxygen Sensor (HO2S) Monitor is an on-board strategy designed to monitor the HO2S sensors for a malfunction or deterioration that can affect emissions. Under specific conditions, the fuel control or upstream HO2S sensors are checked for proper output voltage and response rate (the time it takes to switch from lean to rich or rich to lean). Downstream HO2S sensors used for Catalyst Monitor are also monitored for proper output voltage. Input is required from the Engine Coolant Temperature (ECT) or Cylinder Head Temperature (CHT), Inlet Air Temperature (IAT), Mass Air Flow (MAF), Throttle Position (TP) and Crankshaft Position (CKP) sensors to activate the HO2S Monitor. The Fuel System Monitor and Misfire Detection Monitor must also have completed successfully before the HO2S Monitor is enabled.
• The HO2S sensor senses the oxygen content in the exhaust flow and outputs a voltage between zero and 1.0 volt. Lean of stoichiometric (air/fuel ratio of approximately 14.7:1 for gasoline engines), the HO2S will generate a voltage between zero and 0.45 volt. Rich of stoichiometric, the HO2S will generate a voltage between 0.45 and 1.0 volt.
• The HO2S Monitor evaluates both the upstream (Fuel Control) and downstream (Catalyst Monitor) HO2S for proper function.
• Once the HO2S Monitor is enabled, the upstream HO2S signal voltage amplitude and response frequency are checked. Excessive voltage is determined by comparing the HO2S signal voltage to a maximum calibratable threshold voltage.
• A fixed frequency closed loop fuel control routine is executed and the upstream HO2S voltage amplitude and output response frequency are observed. A sample of the upstream HO2S signal is evaluated to determine if the sensor is capable of switching or has a slow response rate.
• An HO2S heater circuit fault is determined by turning the heater on and off and looking for a corresponding change in the OSM and by
measuring the current going through the heater circuit.
• The MIL is activated after a fault is detected on two consecutive OBD II drive cycles.

More Information

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Information for specific makes

  • P1151 AUDI Bank 1 Long Term Fuel Trim Range 1 Lean Lower Limit Exceeded
  • P1151 BMW O2 Sensor Heater Circuit Signal Intermittent Bank 2 Sensor 1
  • P1151 CHRYSLER Fuel Rail Pressure Malfunction Maximum Positive Deviation
  • P1151 DODGE Fuel Rail Pressure Malfunction Maximum Positive Deviation
  • P1151 FORD Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2  
  • P1151 HYUNDAI Electronic Throttle System Main Accel Position Sensor 2 Malfunction
  • P1151 JEEP Fuel Rail Pressure Malfunction Maximum Positive Deviation
  • P1151 LINCOLN Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2  
  • P1151 MAZDA HO2S-21 Lean Condition Correcting For Over Rich Condition
  • P1151 MERCURY Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2  
  • P1151 MINI O2 Sensor Heater Circuit Signal Intermittent Bank 2 Sensor 1
  • P1151 SUBARU Rear Oxygen Sensor Heater Circuit High Input
  • P1151 SUZUKI HO2S21 Circuit Low Voltage Shift/High Voltage Shift/Circuit Continuity/High Voltage
  • P1151 VOLKSWAGEN Bank 1 Long Term Fuel Trim Range 1 Lean Lower Limit Exceeded

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