Engine codes Po171 Po174 Po401

Those codes mean your engine is running too lean - P0171 for bank 1 and P0174 for bank 2. And yes, very definitely leaving a bolt out of the intake plenum will cause a lean condition because unmetered air is getting into the engine. So you're going to need to take it apart again and reassemble it correctly - with all the bolts and connections as they were before you took it apart.

171 is a HEGO sensor unable to switch/ 174 is for HEGO sensor also.. 401 is insufficient EGR flow!! egr valve may be clogged or need replaced!!

The codes mean the fuel system mixture is too lean. The most common cause is low fuel pressure.

Lean bank 1 and bank 2 , and throttle actuator system fault. Check reason for lean codes 1st, vacuum leak(s), air inlet boot and hoses, or low fuel pressure / clogged filter. Repair as needed then clear codes and recheck .

PO171 and P1131 point to lean codes on bank PO174 and P1151 point to lean code on bank PO305 is missfire on cyl 5

the lean codes is probably a vacuum leak or maybe a MAF sensor is bad or dirty

missfire is dependant on engine if a V10 it may be a coil actually pretty likely on the modulars not uncommon thats for sure
sorry forgot to add that its says missfire on #5 cant remember if that one is the first on the left or last on the left facing the engine vacummn leak could be those dang auto hubs got it stuck in the mud and they did not engage I need to buy some new ones took them apart to clean them out this summer

This is a tough one could be mass air flow sensor ,oxyegen sensors,a fuel filter. a vacum leak, a pcv valve if i missed anything just google po 171 &174 look for fix ya this issue has been addressed many times first check the vacum lines includeing the line on the pcv valve for cracks or splits in the lines .I would do the fuel filter if it hasnt been changed in the last couple of years , if still a problem the MAF sensor if your happy with my advise please leave me with great feedback

You should be replacing all upstream oxygen sensors,
the ones at the inlet or pipe before the converter,on all
your vehicles at 100,000 miles

Go to Rock Auto.Com & buy two & install yourself

NTK 22060 $26.79 ea

The Code 401 is saying there is no flow to the EGR. The other 2 codes say both sides of the engine are running lean.

You can look for Vacuum diagrams for your model car and get some photos to see routing.

What you might do is use a digital camera and try to find a car in a Salvage yard with the parts you need attached. Photo them and then take the hoses and solenoids off the Salvage car and add them to yours.

This would be the cheapest and most complete way of doing this. Unless you can find a shop willing to install used parts to your car. Now some Body shops routinely use Salvage parts for Bodywork. One may be willing to do a little mechanic work to help you. They do mechanic work to replace broken engine parts from accidents, so working on engines is just part of the job.

Hi

Please check the link to get a detailed idea about the code:-

http://www.obd-codes.com/p0421

Please get back to us if you have further query else please accept the suggestion.
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P0174 means Fuel Trim too Lean (Bank 2)

P0401 means Exhaust Gas Recirculation Flow Insufficient Detected

P0420 means Catalyst System Efficiency Below Threshold (Bank 1)

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