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Experience:  30 yrs experience ase cetified tech shop owner
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chevy: 2002 chwvy van 5.7L has trouble code po306

Resolved Question:

2002 chwvy van 5.7L has trouble code po306
Submitted: 4 years ago.
Category: Chevy
Expert:  Chevy expert replied 4 years ago.

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This can be caused by quite a number of things very often no you'll find that a faulty fuel injector were clogged catalytic converter will be to blame we need to do some testing to try to pin it down first Perform a fuel injector balance test for all cylinders. If a fuel injector concern exists, The engine computer recognizes all the extra oxygen and adds fuel to the engine bank. This is verifiable by higher injector pulse on the affected bank. Use the scan tool to turn off the fuel enable. This is found using the special functions/output controls of the scan tool. This will maintain fuel trim numbers at 0%. Check for the entire bank to stop misfiring and concentrate on a single cylinder misfire. The single cylinder misfire can be the cause of the O2 sensor showing lean exhaust.
Check for excessive exhaust backpressure. This can affect only one bank if equipped with 2 catalytic converters. This is often verifiable by reduced injector pulse on the affected bank. Swap the position 1 O2 sensors side to side to see if the misfires move to the other bank of the engine. If so, replace the O2 sensor. Remove bank 6 spark plugs, check for rich or lean plug condition, clean or replace.
Disconnect both front O2 sensors, road test. This will also keep the fuel trim numbers at 0%, similar to step #2. Remove both front O2 sensors and road test. This will verify that the exhaust is not only slightly restricted

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