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P1152 Code – What Does It Mean & 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.


P1152 is an OBD-II Code that indicates the Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 2.


A P1152 code is the result of the ECM (Engine Control Module) receiving a signal from the Bank 2 O2 sensor that it is not reading correctly. The ECM will use this information to determine whether or not fuel trim corrections are being made by the front and rear O2 sensors of bank 2. When the A/F sensor output voltage deviates from the PCM’s expected value, code P1152 is set.


Common causes for this code include:

  • Faulty upstream heated oxygen sensor bank 2
  • Air leaks after the MAF or PCV or between them, which would cause a lean condition resulting in Rich Bank 2.
  • Bad MAF sensor 
  • Faulty fuel pump 
  • Lack of Upstream heated Oxygen Sensor Switch Sensor Indicates Rich Bank 2. 
  • Bad PCM (less likely)
  • Vacuum leak on engine


Symptoms of P1152 can include any or all of the following:

  • MIL (Malfunction Indicator Lamp) is ON 
  • Engine may lose power 
  • Possible black smoke from tailpipe that smells rich 
  • Possible power loss or high emissions, especially on long inclines


To diagnose a P1152 DTC code, you will need to diagnose the oxygen sensors first, as that is what this code relates to.

  • Do a visual check on all vacuum and fuel lines for any damage, leaks and loose connections 
  • You can start by visually inspecting your air filter; if it is extremely dirty or blocked, this would affect A/F readings 
  • Visually inspect the MAF sensor for dirt, dust, or debris 
  • Visually inspect the PCV valve for dirt, dust, or debris 
  • Check all wiring for any signs of damage (check especially around the MAF, PCV, and O2 sensors) 
  • Check the intake boot between the throttle body and air filter; it should be free of cracks or tears 
  • Check that the EGR system is clean and clear 
  • Check that there is no exhaust gas leaking into the engine through an external source, such as a misadjusted valve, cracked manifold, etc.

Common mistakes

The following are common mistakes when diagnosing the trouble code P1152:

  • Using an analog multimeter to test for Oxygen Sensor voltages; These are not accurate enough to yield results. 
  • Not testing Bank 2 oxygen sensors; You should always check all three sensors, as this is what codes P0420 and P0430 relate to.

How serious is this?

A car with a P1152 trouble code will run poorly, or not at all. Since the car will be running rich (which means that there is too much fuel for the amount of air), it may seem like you are losing power; this would be because the O2 sensors are calling for more gas, which cannot be met. After all, you already have too much in. The check engine light should come on when this code sets, indicating that something is wrong with the emissions systems.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Change the upstream heated oxygen sensor bank 2
  • Repairing or replacing air leaks after the MAF or PCV or between them 
  • Replacing the MAF sensor 
  • Replacing the fuel pump 
  • Secondary air injection system repair or replacement
  • Replacing the PCM, though this is rare. By far, eliminating vacuum leaks on engines is one of the most common solutions to this trouble code. Make sure to have your car re-tested by an automotive technician once repairs are made for a more accurate diagnosis.

Related codes

P0420, P0430, and P1131

How much does it cost to fix the P1152 code?

Typically, this trouble code calls for a minimum of $200-400 in repairs and diagnostic work.


In conclusion, the P1152 is a trouble code that relates to the heated oxygen sensors of bank 2. When the voltage deviates from the expected value, this code is set; other possible causes include vacuum leaks on engines or leaking after MAFs or PCVs. The car will typically need at least $200-400 in repairs for this trouble code to be resolved, though it is unlikely that you would have an issue with your PCM.

P1152 Code – What Does It Mean & How To Fix It