Question about 2002 Toyota Tundra

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Check engine light is on. code is p0171

I have already relace the two cat converters and 1 o2 sensor. this code seams to indicate a bad or dirty maf sensor. How hard is it to replace or should i just bring it to a mechanic?

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P-0171 is a dirty Mass Air Flow sensor.

It is located in the intake air tube. Remove the wiring connector, and remove it from the intake. With a flashlight, examine the interior of the sensor. You will see 2 small wires with fuzzy stuff on them. This is your problem. The fuzzys are compromising the wire's ability to measure the air flow. Using a spray cleaner (throttle body or brake cleaner works best), spray the interior of the sensor until it is nice and clean. Do NOT use compressed air to clean it, you will damage the sensor. Replace it and plug it it, the light will go out shortly thereafter.

The graciousness of a FIxYa rating for this assistance would be greatly appreciated.

Posted on Jan 22, 2009

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2 Answers

Check engine light on, scan code p0175. I already change MAF and check O2 sensors. have you any advice?


code p 0175 refers to system too rich bank 2===causes --intake blocked ---EVAP canister purge valve ---fuel pressure ---EGR system---injector/s ---HO2S
basically you changed the wrong sensor as the HO2S sensor is the sensor in the exhaust manifold or before the cat converter
It tells the ECM to adjust the injector flow for that bank to a leaner mixture (O2 sensors are after the cat and tell the ECM if the mixture is right for complete burn
it could be from a bad injector that is leaking at the tip and the ECM cannot control the fuel mix

Jan 21, 2016 | 2006 Hyundai Tucson 4WD 2.7L V6

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My check engine light is on. it is pulling 4 codes P0302 P1670 P0174 P0171


code p 0302 is a misfire on no 2 cylinder
check that the plug lead is on properly, that the lead is operational
move the injector from 2 to another cylinder and see if the misfire follows the move
code p 0174 refers to system too lean bank 2===causes intake /exhaust leak---fuel pressure / pump---injector/s--AIR system--hose connection/s
code p 0171 refers to system too lean bank 1=== causes intake /exhaust leak---AIR system---MAF/VAF sensors---fuel pressure / pump---injector/s -- HO2S
You stated that you replaced the O2 sensor but that is different to the HO2S sensor , does a different job and controls the air/fuel mixture from the ECM
because it has banks 1 and 2 it is a v engine and you will have a HO2S in the exhaust manifold or before the cat converter for each exhaust
O2 sensors are after the cat converter and confirm the HO2S settings for the ECM
to put the lights out , use a scan tool to reset the ECM

Jan 15, 2016 | Cars & Trucks

1 Answer

Engine check light on error code 1 is P0171 system too lean bank 1 error code 2 is P0174 system too lean bank 2


P0171 system too lean bank 1
P0174 system too lean bank 2
links to information on the codes

it means that the O2 sensors in your vehicle detected a lean condition in their respective banks. this could be caused by a dirty MAF (mass air flow) sensor or a vacuum leak downstream from the MAF sensor

sometimes you can clean the MAF with electronics cleaner or brake cleaner but be sure to take it off the vehicle first. be careful not to damage the MAF while spraying the cleaner, and allow it to dry completely before installing it on the vehicle.

May 21, 2011 | 2001 Jaguar S-Type

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I have five codes P2237 P2196 P2271 P0030 P0171 and a P2237 pending code on a 2005 elantra.The car runs poorly, bad gas mileage, sluggish with the check engine light on.Are all O2 sensors bad or maybe the...


P2237 P2196 P2271 P0030 P0171

These are all O2 sensor trouble codes, except P0171 which is a fuel trim code,

You have a bad 02 sensor - up stream - Bank 1 Sensor 1.

Replace it, then road test. The engine computer has a 'default' fuel trim it uses when an O2 sensor fails so it can protect the catalytic converter. If this hasn't been going on too long, good chance simply replacing the O2 sensor will remedy your problem.

Feb 06, 2011 | Hyundai Elantra Cars & Trucks

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2000 GMC Jimmy. OBD2 code P0171. Whats wrong?


system too lean(bank 1). the maff sensor may be dirty or bad. to clean it , remove from vehicle and go to any auto parts store and buy a can of maff sensor spray. be very carefull not to touch inside of sensor, the best way to do it is to place on a clean rag and then clean it. put back on car when dry. this usually does the trick. Inspect all vacuum lines and the vacuum line from pcv valve. also make sure airfilter is clean and free of dust. if above does not solve problem, check fuel filter. hope this helps, follow directions on can to clean maff sensor.

Jul 20, 2010 | 2000 GMC Jimmy

1 Answer

P0137 p0171 p0174


P0137 o2 circuit low voltage bank 1 sensor 2 --o2 sensor after the cat converter -check for faulty o2 sensor -short or open circuit exhaust leak near sensor or plugged cat converter ----P0171 and P0174 -system too lean bank 1--and system too lean bank 2 they are usually from the same problem which can be caused from the o2 problem but check ur maf sensor connections and or clean if necessary[carb cleaner] vacuum leak downstream from maf sensor also inspect pcv lines

Feb 16, 2010 | 2003 Chevrolet Silverado 1500

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Having problem with check engine light its showing that theirs a lean on bank 2 code P0174/P0171 what would be the cause could it be my cadaylac converter


what this codes indicates is you are running lean on both sides of the motor 171 is right side and 174 is left side.

Lean means either low fuel pressure or big vacuum leak. Since you have no cylinder misfires I would inspect the MAF sensor first. If you installed a K/N filter the oil on it could of contaminated the MAF sensor fine wires. Or you may have a air filter that is clogged.
You can clean the MAF with brake clean being careful not to break the wires.
Or inspect for a large vacuum leak that could affect both sides.
Or if all else fails have the fuel pressure checked.

14.7.1 part air to 1 part fuel is what the computer tries to maintain
.It needs this to get the best bang for the buck

A big vacuum leak or low fuel pressure will change this
If the computer sees a big vacuum leak it will add fuel until it cant anymore. This is when the code sets.
Same thing for low pressure. It will set the code because the engine stays lean for too long.

Dec 02, 2009 | 2003 Chevrolet Tahoe

2 Answers

Lincoln navigator 98 I have a code p0171 bank1


P0171 - System Too Lean (Bank 1) indicates a bad reading from an O2 sensor or bad MAF sensor.
CausesA code P0171 may mean that one or more of the following has happened:
  • 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 SolutionsPossible solutions include:
  • In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
  • Inspect all vacuum and PCV hoses, replace if necessary
  • Check for a dirty fuel filter and proper fuel pressure

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Check Engine light is on my 1997 F150 with a small V-8. The tester returns codes P0171, P0172, P0174 and P0175. What does all this mean?


those codes are for lean engine condition look for vac leaks at the back of engine to the pcv valve could hear hissing noise with engine running also check egr valve to be stuck open also when was last fuel filter changed? hope this helps .

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3 Answers

Check engine light on a 2001 Toyota Corolla


No need to replace the MAF. If it was bad, the check engine light would have come right back on as soon as you started the engine. The MAF not only measures the air going into the engine, but also measures the air temperature. Those 2 circuits are constantly sending info the the ECU. If either would fail, the ECU would light the check engine light. P0171 is a common code for incorrect readings (dirty) in the MAF. Cleaning it always helps, and cuts off the light. Your acceleration problem may be either a wrong Air-Fuel sensor (the one before the cat), or an "aftermarket" AF sensor. "Aftermarket" AF sensors have been shown to not work properly in Toyota vehicles. Hope this helps

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