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P1151 Code on 1999 Mercury Cougar 2.5L V6: Causes, Fixes, and Smell of Eggs

Model: manufaturer Fault Code: P1151 Posted: 2010-08-10 17:02

Hi everyone, I'm having an issue with my 1999 Mercury Cougar 2.5L V6. About a month ago, I started getting the P115-1 diagnostic trouble code along with two other codes. The car was bucking at around 2000 RPM and was emitting black smoke. After replacing the Mass Air Flow (MAF) sensor, the symptoms stopped temporarily — the engine ran smoothly and the check engine light went off. However, after resetting the system, the check engine light returned, and now I only see the P1151 code: 'Manufacturer Control Fuel Air Metering'. I've looked up this code, and it appears to have over 100 possible interpretations. What does this actually mean in practical terms? Is it related to fuel mixture being too lean or rich? Additionally, I notice a strong egg-like odor when exiting the vehicle — could this be connected to the engine issue? Any simple explanations or troubleshooting steps would be greatly appreciated. Thanks, Ron

Related fault codes
P1151
Comments (5)
Anonymous 2010-08-11 08:06

P1151 typically indicates an insufficient switching response from the upstream O2 sensor on Bank 2 (driver's side). Given that your vehicle is over 11 years old, it's likely this sensor has degraded. Replacing the upstream oxygen sensor on Bank 2 is a common fix. I recommend getting the part from an authorized dealer to ensure compatibility and reliability — aftermarket sensors can sometimes cause recurring issues or fail prematurely. Let me know how it goes!

Anonymous 2010-08-13 04:42

Thanks for the advice! I'll try replacing the O2 sensor on Bank 2. Will update you once I've done it and see if the code clears out.

Anonymous 2012-09-05 23:51

I have a 2000 Mercury Cougar V6 with the same P1151 code. I’ve already replaced the O2 sensor on Bank 2, changed my fuel filter, installed new spark plugs and wires, and cleaned the MAF sensor — but the code still appears. What did you do to resolve it? Any other steps I should try?

Anonymous 2012-09-06 05:11

Where did you purchase your O2 sensor? What brand is it? Did you check for any vacuum leaks before replacing the sensor?

Anonymous 2012-09-06 12:52

I bought the O2 sensor from AutoZone. It's a Bosch brand. The only leak I noticed was in the PCV valve, which I replaced as part of my maintenance routine.