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Q: Check engine light with codes 171 & 172.Shop said manifold gasket? on 2003 Chevrolet Suburban 1500

Check engine light came on, took it to the shop & they said code 171 & 172. They said needs new manifold gasket & injector cleaning. Truck has been running perfect. Has 160,000 miles with regular maint performed.
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Agree with greg, does it misfire when first started cold, then smooth out after a few seconds, also indicative of an intake gasket leak!
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both lean codes,did they ck mass air flow sensor? could be intake leak,always use updated intake gasket from dealer
P0171 is a lean code and P0172 is a rich code. It could be the MAF sensor, but it sounds like it is air leaks. Grab a can of carb cleaner and spray along the edges of the intake manifold. See if the idle fluxuates or stumbles. Also listen to the engine when the vehicle starts up cold and see if you hear any exhaust leaks. An exhaust leak before the O2 sensor will cause problems as well. Try switching sides with the O2 sensors before the cat convertors and see if code(s) P0174 or P0175 set. You may just have a bad O2 sensor. If the code changes whent he sensor is moved, replace the sensor.
We tried the carb cleaner & no stumbles. Would I hear an exhaust leak in the back? what would it sound like? Not sure how to switch the O2 sensors but will see if I can figure it out. Thanks!
An exhaust leak would sound like a ticking noise from the exhaust. Usually will be heard more when cold. Check at the gaskets and pipe connections. To swap/move the 02 sensors, you have to unplug them, then you'll need either a 7/8" wrench or an 02 sensor socket. Do not overtighten the sensors when re-installing them. They just need to be snug, not torqued. Upon removal of the sensor(s), if they are covered in heavy white or black soot or ash, replace them.
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