Question about 2003 GMC Yukon Denali

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Power and fuel mconsumption

My 2003 Yukon Denali XL has 60K miles plus and is lagging in performance and gas millage. I am assuming after changeing the spark plugs that the CO 2 plug should be changed. Is there only 2 plugs? If I change the sensor will the computer need to be reset even thou the check engine light is not lighted?

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If you replaced the plugs, did you replace the plug wires. Even though they are short wires from the coil to the plugs they can go bad. How is the air filter? Have you replaced the fuel filter?

You have four oxygen sensors on your truck. one on each side pre catalytic converter and one after each converter. It is a very pricey replacement because all of the O2 sensors are four wire.

If you change the sensors, your pcm (vehicle computer) will detect the change in readings very quickly. If you really want to ensure the computer completely relearns you need to disconnect the ground for at least 10-30 minutes. When you reconnect the battery the computer will return to its baseline from the factory. It will immediate begin the adaptive learning process to perform in accordance with your driving style.

Another thing to consider is cleaning the mass air flow sensor. This is a very delicate piece of sensor and requires a special cleaner. STP and GUMOUT both sell a specific product for the cleaning of the MAF. Follow the directions. I would be especially concerned if your usinga K & N air filter as the oil from the filter will sometimes coat the MAF and resulting in bad readings.

Good luck.

Posted on Jun 01, 2009

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