Question about 2005 Chevrolet Uplander

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Check code engine po171

Replace the oxygen sensors, hose, fuel pump works well, everything seems fine without vacuum, she runs well but the failure continues (runs 15 miles and the light back on) (P0171 code) if you turn off the engine and wait for 5 minutes the engine will not start. Waits for 10-20 minutes there can start the engine.

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  • Don Garretson
    Don Garretson Apr 22, 2014

    Hi chivopacion f, I want to help you with your problem, but I need more information from you. Can you please add details in the comment box?
    Specifically what the code is.

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    _-__-___-_ Apr 23, 2014

    and what engine under the hood. what size, cylinder count. 3.5 L LX9 V6, 3.9 L LZ9 V6, 3.9 L LGD V6 that code is engine code. why not read the FSM, and see what that DTC means, it tells you the MAF is bad. (or loose wires to it,or just dirty) the book explains what to do, or at ALLDATA.COM log in and read. or things that make the MAF look bad and its not the maf, here is a list, (more tests) The MAF (Mass Air Flow) Sensor is dirty or faulty Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry. There could be a vacuum leak downstream of the MAF sensor Possible cracked vacuum or PCV line/connection Faulty or stuck open PCV valve Failed or faulty oxygen sensor (bank 1, sensor 1) Sticking/plugged or failed fuel injector Low fuel pressure (possible plugged/dirty fuel filter!) Exhaust leak between engine and first oxygen sensor, the code simply means the 02 sensor is stuck lean, more , why not learn to use google, here is one good hit. Random;

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    _-__-___-_ Apr 23, 2014

    the key fact here, is did you run the scan tool full time driving, to see if other codes (DTC) are popping up, 174 after all the car has 2 cylnder banks and 1 oxy sensor on each. and if only one sensor fails, that tells me its an exhaust leak. find it with a rubber hose to your EAR, and hear that putt putt sound, bingo bad exhaust man. or just a bad gasket. the 02 is not fibbing, its sees illegal oxygen, there. causes by 2 things. cracks letting air in, or gross misfire on that side, there are many tests to find it, , why not get an ASE mech. to find it.



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I'd be more concerned at looking into the fact that it takes a while to cool off in order to start up again. P0171/174 codes mean a lean condition. I'd suspect that you may have a problem with Vapor lock on the one bank, which is causing air to form in the fuel rail on that side. Since air compresses, the fuel pressure doesn't necessarily come up enough to restart the engine until the fuel has cooled down enough to stop boiling. Did this start happening once the weather in your area started getting warmer?

Posted on May 08, 2014


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Posted on Jan 02, 2017

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SOURCE: Chevy S10 starts and then shuts off.

well i would try squirting fuel into the throttle body when it is in its not running mode. if it starts and runs you know the fuel pump is at fault .. or its not getting the right fuel pressure from it..

Posted on Feb 10, 2009

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SOURCE: 1999 Chevrolet S-10 Check Engine Light


Posted on Mar 12, 2009

  • 70 Answers

SOURCE: 1996 s10 2.2 engine starts but idles rough and will not rev up.

Hi! You must be frustrated by now! your code is marking that the O2 sensor is bad in bank 1. Did you replace the O2 sensor that is located  before the catalytic converter?  The S10 has an O2 sensor specially made for that cat. its about 30$ That would explain for your blackened spark plugs; your pc on the car is asking for more fuel. GOOD LUCK!!

Posted on Apr 29, 2009

  • 103 Answers

SOURCE: 2004 colorado code p0172

check your gas cap. If you fill your gas while the vehicle is running, it will also cause your light to come on. Go to OReilys or Autozone and they will shut it off for free and tell you the problem

Posted on Jul 25, 2009

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SOURCE: I have a 2007 Equinox check engine light came on i

that car is under warranty for emmision failuare, it a federal law, also you changed wrong sensor poo36 and poo54 mean o2 sensor after the cat-converter is no good not the first one by engine, replace the one after cat and problem will be fixed. good luck.

Posted on Nov 05, 2009

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2001 chevy tahoe code po440, po171

DTC P0171 or P0174
Circuit Description
The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during open and closed loop. During open loop, the PCM determines fuel delivery based on sensor signals without oxygen sensor input. During closed loop, the oxygen sensor inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the oxygen sensors indicate a lean condition, fuel trim values will be above 0 percent. If the oxygen sensors indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, this DTC will set.

Diagnostic Aids
• The system will go lean if an injector is not supplying enough fuel.
• A lean condition could be present during high fuel demand due to a fuel pump that does not pump enough fuel.
• Use a scan tool in order to review the Failure Records . If an intermittent condition is suspected, refer to Intermittent Conditions .
With every DTC a diagnostic flow chart is given for a diagnostic direction .(thing's to test ) For these test's you need a professional or factory scanner ! Plus knowledge of how these system's work would be nice .

Test Description
The numbers below refer to the step numbers on the diagnostic table.
If conditions were not corrected, refer to Fuel System Diagnosis for a possible fuel problem.
If conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the problem.

Did you perform the Diagnostic System Check-Engine Controls?
YES - Go to Step 2
NO - Go to Diagnostic System Check - Engine Controls
Important: If any DTCs other than P0171 or P0174 are set, refer to those DTCs before continuing
Install a scan tool.
Start and idle the engine at the normal operating temperature in closed loop.
Record the Long Term Fuel Trim.
Turn OFF the engine.
Turn ON the ignition, with the engine OFF.
Review the Freeze Frame/Failure Records and record the displayed data for this DTC.
Does the scan tool indicate that the Long Term Fuel Trim is greater than the specified value?
YES - Go to Step 3
NO - Go to Diagnostic Aids
Operate the engine at idle.
Observe the HO2S parameter with a scan tool.
Does the scan tool indicate that the parameter is within the specified range and fluctuating?
200-800 mv
YES - Go to Step 4
NO - Go to Step 5

DTC P0440
The EVAP LARGE LEAK TEST is based on applying vacuum to the EVAP system and monitoring the rate of vacuum decay. The powertrain control module (PCM) uses the input from the fuel tank pressure (FTP) sensor in order to determine the rate of vacuum decay. At an appropriate time, the PCM turns the EVAP canister purge valve ON (open) and the EVAP canister vent valve ON (closed). This allows the engine to draw a vacuum on the system. At a calibrated time or vacuum level, the PCM turns the purge valve OFF (closed), and tests the system vacuum. If the system is unable to achieve the calibrated vacuum level, the PCM will set DTC P0440.
This could be caused by a leaking purge valve . Do you know what that is ? Mounted on the engine ,under the plastic engine cover . Disconnect the hose that goes to the vapor canister under the back of the vehicle . With the engine running see if you can feel vacuumn . If you do replace it .

Dec 15, 2017 | Chevrolet Tahoe Cars & Trucks

1 Answer

I have the codes are po171 ..po174

code p 0171 refers to system too lean bank 1===causes --intake /exhaust leak---air system---MAF/VAF sensor--fuel pressure / pump---injector/ s---HO2S
code p 0172 refers to system too rich, bank 1===causes --intake blocked ---EVAP canister purge valve --fuel pressure --EGR system---injector/s -=-- HO2S
code p 0173 refers to fuel trim(FT) bank 2--malfunction===causes --intake leak---air system--fuel pressure /pump---injector/s --EVAP canister purge valve---HO2S
code p 0174 refers to system too lean, bank 2===causes intake / exhaust leak---fuel pressure /pump---injector/s---Air system---hose connection/s
I was not sure if you wanted all codes or just the first and last, however you will see that there are some common problems that may help point you in the right direction
1-- is the heated oxygen sensor (HO2S) which is the sensor before the cat converter
2--is the fuel pressure , so a fuel pressure test will determine if a regulator or fuel pump problem,
3--EVAP canister purge valve --replace as required
4--intake / exhaust leak --check for vacuum hose failure including hoses to vent controls and check the flexible exhaust connection before the cat converter for leaks
The rest are there to check if you haven't fix the fault before you get to them

Nov 05, 2015 | Cars & Trucks

1 Answer

What is po171 code mean

PO171 means the engine is running lean(that means that the engine is getting too much oxygen rather than fuel)! Although replacing the 02 sensor has a chance of solving it, unfortunately it doesn't always do so.

Are there any symptoms? Rough running at any point? Loss in power? Idle problems?

This could be caused by many things: A vacuum leak, EVAP system not working properly, injector(s) clogged, or fuel pump/fuel filter issue.
There is also a very small chance that the O2 sensors become contaminated by certain types of silicone sealants installed in improper areas of the engine. I think that this last possibility would take a long time to show up in the computer.

Do you have access to an OBD2 scanner that shows live data? If so, I can give you more info how to try and pinpoint this problem.

Oct 09, 2014 | 2001 Ford Explorer Sport

1 Answer

My engine idles and runs fine but has codes po171 and po174

Your still lean on both banks

Either the oxygen sensors failed or slowed
down & set a code or you have vacuum leaks

When ever you remove an intake-- you smoke it before
& after the job-- to avoid vacuum issues

Fuel Trim may give you some idea where to start

Can be rich both banks & driven lean

Dec 17, 2012 | 2002 Ford F150 Regular Cab

1 Answer

My car has code PO171 WHAT DOES IT MEAN?

This means your engine is running too lean on the fuel-air ratio. Get this fixed as it can damage the engine after a while.

Possible causes are

• Air intake leak (hose loose)
• Fuel line pressure low
• Injector blockage
• Heated oxygen sensor malfunction
• Mass air flow meter fault
• Engine coolant temp. sensor failed

The most likely cause is the oxygen sensor

Aug 03, 2012 | 1992 Toyota Camry V6

1 Answer

P 0171 (m)

PO171 refers to "system too lean - bank #1", This means that the upstream oxygen sensor detected too much oxygen in the exhaust. Cleaning out the MAF (mass air flow) housing and sensor will help eliminate the PO171 code. It's also necessary to clean the upper portion of the engine and fuel injectors, to make sure they are not clogged or "fouled." check for vacuum leaks and around intake manifold. spray around manifold with engine running, if it flares up you have a leak. in most cases. cleaning the MAF sensor does the trick !

May 03, 2012 | Jeep Grand Cherokee Cars & Trucks

2 Answers

Help on finding out wind star coads PP0171-/-P074-/-P0401

first PO171 o2 bank 1 s1 lean PO174 o2 bank2 lean
PO401 cyl 1 misfire
when an engine misfires the oxygen sensor will read the oxygen from that cyl sensor doesnt read fuel so every misfire is a air pump to diagnose we have to fix misfire first check the coil wires and plugs for cyl 1 use spray bottle with water run engine hot at idle spray wires with water if enging runs rough shakes or stalls then replace the wires dont spray with to much water if the wires are real bad you may not be able to restart engine

try this first once fix misfire clear codes and drive it

plz comment vote reply if you need more help

Jan 17, 2011 | Ford Windstar Cars & Trucks

1 Answer


sounds like EGR valve and sensor this controls idle speed when at a stop. the po171 is a burn lean or rich code need to know what bank 1 or 2. also check for a vacuum leak from one of the hoses.

Aug 07, 2010 | 1998 Ford Contour

3 Answers

Code reading p0171

So your car's CEL (Check Engine Light) is on and you had the codes scanned at a local parts store. Your car has either a P0171, P0174 lean fault code or both stored in the computer, these codes are based on Oxygen Sensor (O-2) readings. A lean code or codes indicate that there's too much oxygen in the exhaust. Remember parts stores have employees that have good intentions but they may not have the experience necessary to interpret what the trouble codes really mean. These codes are based on oxygen measurements in the exhaust. A common mistake with lean codes is to replace the oxygen sensors. This could be a very expensive mistake that will not fix the problem. Especially if both codes are present, because the chance of both O-2 sensors failing at the same time is very unlikely.
Most likely the cause is a vacuum leak. A vacuum leak can be caused from a vacuum hose, intake gasket or maybe even a leak in the air intake hose from the MAF (Mass Air Flow Sensor). Listen for a hissing sound that may lead you to the source of the problem. Some technicians will use a propane bottle with a hose attachment to help pinpoint vacuum leaks. With today's computers it's not quite as easy to check for vacuum leaks this way because the ECU (Electronic Control Unit) will compensate quickly for the added fuel and a change in idle is harder to notice. Oxygen sensor readings can be monitored with a scan tool while checking for leaks with propane, by looking for increased readings when enriching the mixture. Another way technicians can check for vacuum leaks is with a smoke test. By introducing smoke into a vacuum hose on the engine, the leak will be revealed when the smoke escapes from the problem area.
Aftermarket air filters that use oil on the element can sometimes damage the MAF. Over oiling the air filter may allow some excess to get on the MAF sensor wire or element. This can alter the reading, fooling the ECU into seeing more or less air flow therefore changing the air/fuel mixture incorrectly. I once worked on a car that would not start that had a problem with a MAF. When looking at the wire in the MAF, there was a burned piece of trash that made it's way past the air filter. After cleaning the sensor the car ran perfectly. The ash that was on the MAF sensor wire was altering the reading by enriching the mixture so much that the car could not run. After talking with the customer, he said the air filter was just changed. This was obviously when some trash got into the air intake hose that settled on the hot wire of the MAF.
Fuel Pressure could also cause a lean condition. If the fuel filter is clogged or the fuel pump pressure is low, there could be higher level of oxygen in the exhaust also. Most of the time though, the ECU will compensate for the reduced fuel volume. So this is one of the least likely causes of a lean code.

Nov 20, 2009 | 2003 Pontiac Vibe

4 Answers

P0171 and p0174 codes

P0171 System too Lean (Bank 1)
P0174 System too Lean (Bank 2)

If a car has a check engine light on and has P0171 and P0174 codes stored, the most likely cause is a vacuum leak. These codes are set by the car’s computer when it sees too much oxygen in the exhaust. Excessive oxygen readings in the exhaust will set lean codes. This does not mean that the oxygen sensors are defective. It is a common mistake for people to replace oxygen sensors when lean codes are present. Just because the code is related to oxygen sensor readings, it doesn’t mean that the oxygen sensors are bad. If both of these codes are stored this means that both banks of the engine have excessive oxygen in the exhaust. If the oxygen sensors are replaced it’s most likely that the same codes will reappear. It is very uncommon for two oxygen sensors to fail at the same time.

Therefore the most likely cause of P0171 and P0174 codes is a vacuum leak. The source of a vacuum leak can be one of many things. The most common cause of a vacuum leak is a leaky hose. Vacuum hoses over time can become dry and brittle. The rubber deteriorates and can leak causing a vacuum loss. Many times a leaky vacuum hose can be found by listening for a hissing sound. A large vacuum leak can even make the car run rough at idle. In some cases it will not idle without feathering the gas pedal.

Sep 10, 2009 | 2002 Jaguar X-Type

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