Old post but any luck with fix?
Posted on Oct 29, 2021
Lean code doesn't always mean it has a vacuum leak, if the engine is misfiring, it can cause it to run rich, and therefore the ECM make the engine run lean to compensate, and thus throwing the code. Not saying it ISN'T a vacuum leak, there is that possibility as well. Injectors not spraying as the should could also cause lean conditions (and the random misfire). An exhaust leak before the O2 sensors can cause the lean conditions. Even a O2 sensor reading incorrectly can cause the lean code to show up (unlikely that both O2's went bad at same time though). If you have access to a scanner i would review the live data, and monitor which cylinder(s) is misfiring and the O2 sensor data. Maybe its time for a tune-up!!
Posted on Mar 02, 2015
Sounds like you have a serious vacum leak.; DTC 0174 and 0174 are lean conditions on bank 1 and bank 2, 0300 is random misfire. The only thing I can think of is a big vacum leak like the brake booster / vac line leaking, or maybe the intake manifold is cracked ... even a stuck-open EGR doesn't normally lean a motor that much. Start by checking for a vacum leak, if the motor will idle you can spray a little WD-40 around ports and lines >> if the idle speeds up or becomes smooth you on the right track in the area you judt sprayed.
Posted on Feb 26, 2015
SOURCE: lack of fuel when accelerating
This might help. It looks like you O2 sencor had gone bad or the signal has and causing multiple mis fire. according to your codes.
PO171 System too Lean (Bank 1
PO174 System too Lean (Bank 2)
PO300 Random/Multiple Cylinder Misfire Detected
Causes of PO300
Fuel injectors, related wiring, sensors and computer issues
Running out of gas, or poor fuel quality
Evaporative emissions system (EVAP) concerns: fuel vapors leaking into engine
Incorrect Fuel Pressure
EGR system concerns
I'ld start with chaning the O2 sensors first but sheck for bad wire connection. Hope this helps and good luck
Posted on Apr 08, 2009
SOURCE: check engine light on,running rough and stalling.
means you have multiple misfires (po300) the other codes are lean codes, possiable tune up , bad injector, fuel pump,
Posted on May 07, 2009
SOURCE: codes p171 and p0174 on a chevy truck?
Subject: 97-05 Vehicles with 4.8 5.3 5.7 and 6.0 Gen III V8 Engines and Misfires on One Bank - kw CEL diagnostics driveability DTC P0171 P0172 P0174 P0175 P0300 P0301 P0302 P0303 P0304 P0305 P0306 P0307 P0308 #PIP3056 - (07/12/2004)
Models: (00-05 Cadillac Escalade - C6 and K6) and (02-05 Chevrolet Avalanche - C1, C2 K1 and K2) and (99-05 Chevrolet Silverado - C1, C2 K1 and K2) and (00-05 Chevrolet Suburban - C1, C2, K1 and K2) and (00-05 Chevrolet Tahoe - C1 and K1) and (99-05 GMC Sierra C1, C2 K1 and K2) and (00-05 GMC Yukon - C1, C2, K1 and K2) and (03-05 Chevrolet Express G1, G2, G3, H1, H2 ) and (03-05 GMC Savana G1, G2, G3, H1, H2 ) and (04-05 Buick Rainier S1, T1 ) and (03-05 Chevrolet Trail Blazer EXT S1, T1 ) and (03-05 GMC Envoy XL XUV S1, T1 ) and (03-05 Hummer H2) and (04-05 Cadillac CTS-V DB) and (98-02 Chevrolet Camaro FB) and (97-04 Chevrolet Corvette YB) and (98-02 Pontiac Firebird FB) and (04-05 Pontiac GTO VB)
The following diagnosis might be helpful if the vehicle exhibits the described symptoms.
Condition/Concern:
Check Engine Light with a P0300 due to 2 - 4 cylinders misfiring on the same bank of the engine. DTCs P0171, P0172, P0174 or P0175 may also set for the misfiring bank.
Recommendation/Instructions:
If the published misfire diagnostic does not isolate the cause, perform the following suggestions as necessary:
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
NOTE: GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition.
Posted on Sep 30, 2009
SOURCE: odb2 reading codes p0171, p0174, p0300. running
Hi:
Posted on Dec 11, 2009
SOURCE: what do these trouble codes mean p0171 and p0174
po171 is system too lean,bank 1,po174,is system too lean,bank 2,It sounds like a fuel pressure problem.
Posted on Jan 05, 2010
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