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Repair guides and support for the first generation Grand Cherokee ZJ, an upscale mid-size SUV built by Chrysler's Jeep division.

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trouble code lean on bank 1

My 97 jeep grand Cherokee 4.0 4x4 check engine light was on and auto zone scanned it and said i had lean on bank1 what could be the problem and where on the engine exactly is bank 1.

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what was the actual code you got from the scanner?


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1 Answer

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jacob, those can be caused by a vacuum leak around the intake as well as many other things. Check your plugs and see what they look like. Most likely some soot on those. Make sure that you get new plugs, check for vacuum leaks. After that check your O2 sensor. Unplug the front O2 sensor and see if it makes a difference (it should) if not I would suggest you replace it. Since those lean codes originate when PCM (engine computer) cannot adjust the fuel mixture to achieve a 14.7 to 1 ratio. It keeps having to adjust the injector pulse up and when it reaches + 33% short term adaptive, it then sets those codes. Can be a bad fuel filter, bad fuel pump etc. So, try one thing at a time.

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