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david
david, Auto Service Technician
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Experience:  Certified Master Technician,Certified in diesel & gasoline engines
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Mazda 6 check engine light on with P0171 code

Customer Question

Mazda 6 check engine light on with P0171 code
Submitted: 4 years ago.
Category: Car
Expert:  Dino replied 4 years ago.

hello welcome to the site

the p0171 is a lean condition .

how many miles on the car ?

what service work has been done prior to this code appearing

Customer: replied 4 years ago.
115K and there is a K&N cold air intake on the car, the check engine light came on immediately as this was installed. We called K&N to get help and check to ensure the cold air kit was installed properly (we believe it is based on their feedback and PDF they sent us) however the check engine light didn't come on until this was installed. Worse news is we dont have the OEM parts anymore to go back to the OEM setup. We have tried blocking 75% of the airflow on the cold aitr intake (dick tape on the intake filter) to make it richen up but still shows too lean on sensor banks one and two. We checked for vacumn leaks with starter fluid on / around hoses but no joy.... Thoughts?
Expert:  Dino replied 4 years ago.

ok please check to make sure the sensors don't have any oil on it from the filter.

if a filter has to much oil on it theirs a chance this will get on the sensor and alter the readings.

 

im 100% agree with you on the intake problem.

all your hoses are hooked up correctly ?

did k&n offer any help on this ?

 

Customer: replied 4 years ago.
I cleaned the MAF sensor with MAF cleaning solution, hoses appear to be hooked up correctly yes. K&N was basicly useless, told us it was certified to work in the car and the cars computer would compemsate for the additional cold air intake. The odd thing I find here is that both sensor banks show too lean. What is common about both banks ??
Expert:  Dino replied 4 years ago.

the intake is the common thing here.

i could see if this was isolated to 1 bank but 2 is a concern.

 

Customer: replied 4 years ago.
Thoughts?
Expert:  Dino replied 4 years ago.

well other then rechecking every hose and clamp i can amagine something with the air filter but i have seen some in the acuras cause intake issues.

with out me seen this first hand i have to go on the info you have given me.

was their a order on the hoses you removed on the stock intake?

Customer: replied 4 years ago.
An order?? Not sure I understand the question
Customer: replied 4 years ago.
We removed the houses from the air intake box first (relay with two hoses), then the MAF sensor, then the temp sensor).

here is the filter we installed http://www.car-stuff.com/carparts/mazda620042007k-and-nk33696026ts390147.html
Expert:  Dino replied 4 years ago.
ok this is the cold air intake and does down into the engine or its a short ram intake ?
Customer: replied 4 years ago.
no full lenght all one stainless steel tube wi
tube with a 6" rubber tube that connects it to the intake. new clamps and tested with starter fluid for leaks there as well
Expert:  Dino replied 4 years ago.

mmm this is very odd.

i have seen issues on the cold air that drops down into the engine or bummer area.

did the intake temp sensor fit into the grommet ?

 

Customer: replied 4 years ago.
not sure i'll look.i actually had a professional install the cold air intake kit. i m not even sure where the temp sensor is located.
Expert:  Dino replied 4 years ago.

hmm now you have me in a tail spin.

this is a sensor that is on the actual intake piping.after the maf.

 

Customer: replied 4 years ago.
when you say after you meantowards engine or btwoards air filter (front of car)
Expert:  Dino replied 4 years ago.

yes towards the engine. after the air filter leading to the throttle body

how did the acura turn out ?

Customer: replied 4 years ago.
getting ready to put in coil now
Expert:  Dino replied 4 years ago.

ok.

 

Customer: replied 4 years ago.

Time to drive to autozone and buy part 1 minute

Time to change ignition coil 7 minutes

Expert advice .... Priceless !!

 

Thanks man... now fix my mazda speed 6 and I'll triple your price !!

Expert:  Dino replied 4 years ago.

thats great news glad the acura is running.

can you take a picture of the intake and all the hoses ect so i can get a birds eye view of the intake something just does not make sense here.

 

Customer: replied 4 years ago.
Sending you some pics in a second... you can't see much and I dont see anything I can make out to be a temp sensor. I see a MAF sensor and I see a relay that went to the OEM airbox (that the directions tell you to mount to ground it but don't show any hoses going to it. Here is the instructions we got for it. http://www.knfilters.com/instructions/69-6026_inst.pdf
Expert:  Dino replied 4 years ago.

ok i will look this over.

 

Customer: replied 4 years ago.
Pictures....graphicgraphic
Customer: replied 4 years ago.
if you can't make out the pictures get me a real email address and I'll just forward them all to you
Expert:  Dino replied 4 years ago.
what about the maf sensor. which direction is is pointing ?
Customer: replied 4 years ago.
keyed so its impossible to put in but one way only
Expert:  Dino replied 4 years ago.

the directions show a couple of hoses do you see these ?

the intake clamps look good.

can you run your hand around the intake piping and do you feel any fittings ?

Customer: replied 4 years ago.
yes there are two of them, one goes to some type of plastic one way valve the other goes to a semi rigid hose that appears to go under the intake manifold cover.
Expert:  Dino replied 4 years ago.

and you cleaned the maf sensor was it dirty ?

Customer: replied 4 years ago.
it was not dirty but yes to be safe I cleaned it
Expert:  Dino replied 4 years ago.

ok well im not sure what else i can suggest on this.

im out of ideas on this.

i can re open this up to see if another expert has some ideas.

i have not see something so simple create so many problems.

i really don't see what else could be causing this besides the intake unless the shop broke something while installing the intake.

with out taking this all apart again and inspecting for damage or anything out of place.

Customer: replied 4 years ago.
I agree... can we open this up to others perhaps two heads are better than one?
Expert:  Tom replied 4 years ago.
Ok there are no signs of vacuum leaks correct?Is there a leak at the flex exhaust pipe?
Customer: replied 4 years ago.
no leaks anywhbere that we can find
Expert:  Tom replied 4 years ago.
If you install the factory intake will the light go out?
Customer: replied 4 years ago.
would love to be able to do that but we threw it out and at $750 for OEM replacement this is not an option. either way we need / want to keep the cold air intake.
Expert:  Tom replied 4 years ago.
Do me a favor swap the blue and black hose clear and see if the Light comes back on.Also check the pcv hose on the firewall side of the engine these are known to crack.

Edited by Cardoctor74 on 6/21/2010 at 3:38 AM EST
Customer: replied 4 years ago.
pvc valve was replaced last month when it went bad and was causing the engine to burn massive amounts of oil. of course the check engine light had been on for 9 months before tha not sure it they will reach to swap but ill certainly try
Expert:  Tom replied 4 years ago.
Check the hose to the pcv valve and see if tis cracked.
Customer: replied 4 years ago.
not that i can tell and spraying starter fluid on or near it with engine running does nothing
Expert:  Tom replied 4 years ago.
Ok I would still physically check it if you could.
Customer: replied 4 years ago.
ok appears slightly soft but no visible cracks
Expert:  Tom replied 4 years ago.
Ok it sill can be pouress and if it is will cause this code.
Customer: replied 4 years ago.
ok ill replace it, we are talking about the one near the firfewall that is about 4" long and makes a right angle turn correct?
Expert:  Tom replied 4 years ago.
Yes correct.Let me know then clear the code and see if it comes right back.
Customer: replied 4 years ago.
Relist: I still need help.
Error Code P0171 on 2004 Mazda 6
Expert:  Tom replied 4 years ago.
What was done since we last spoke ?
Customer: replied 4 years ago.
what you requested, that we replace that pcv hose. i ordered it and had it installed, drove 17 miles after resetting codes and in the am upon cranking the same code is back
Expert:  Tom replied 4 years ago.
At this point I would swap out mass sensor from a salvage yard and see if it makes a difference if not it's there's a vacuum leak or ECM issue.
Customer: replied 4 years ago.
MAF if bad would yeild a different code, plus too expensive to shotgun troubleshoot. ECM issue seems very unlikely as this started the moment the Cold Air intake was installed. Seems to be more related to the cold air intake. vacuum leak is possible but again where and how to locate
Expert:  Amedee replied 4 years ago.

Hello!

 

New Expert here!

 

Welcome to Just Answer! My name isXXXXX will be happy to help you out and your 100% satisfaction is my goal. Please realize that all my answers are based solely on the info that you provide me with....

 

I have been following this thread and I would like to try and help you out. Sorry for so many questions but I would like to accurately diagnose your lean code. I just need a bit more info from you to point you in the right direction.

 

Do you have access to a scanner that can read live data?

 

How does the engine idle? How does the engine accelerate?

 

Customer: replied 4 years ago.
Yes I do on the scanner, Idles perfect, accelerates like a scared cat =o)
Expert:  Amedee replied 4 years ago.

Ok... good!

 

Lets take a look at the rpm in the freeze frame. I want to see if the code popped up at idle or when the engine rpm was up at higher rpms

Customer: replied 4 years ago.
it was idle but I'll double check. I say this because the whole way home after replacing it the code never came up. I parked the car for the night and the next day as soon as I cranked it the code came up. I'll let you know however.
Customer: replied 4 years ago.
ok freeze data
DTC thtat cased the Freeze Frame
P0174 (yea it use to be P0171)
Throtle position 18%
Barametric Pressure 101 KPA
Load Valve 28.6%
Air Flow Rate 8.65 GR/SEC
Air Intake Temp 100 F
Short Term Fuel Trim1 13.2%
Ign Timing Advance 32.5 Degrees
Long Term Fuel Trim1 20.3%
Vehicle Speed 36mph
Time since Engine Start 1:06 minutes

Expert:  Amedee replied 4 years ago.

Ok.. sounds good!

 

It might take the computerXXXXXcycles to light the MIL light when it sees this lean condition. THat is why is most likely popped up on the 2nd start up.

 

If in fact that it was at idle that this code was flagged, then chances are it is going to be an air or a vacuum leak. There is a difference between the two. A vacuum leak is after the throttle plate. An air leak is before the throttle plate but after the mass air flow sensor. Either way, there is a leak after the mass air flow sensor, the computer will see it as a lean condition and it will flag this code.

 

Again, look very carefully around the after market intake tube or snorkel for any place that air can enter that would not be accounted for by the mass air flow sensor.

 

If none is found, the best way to go about this diagnoses is to smoke check the intake for vacuum leaks with a smoke machine. THis makes it really easy to find air or vacuum leaks. However, before we get that far lets just get a good visual of the intake set up after the mass air flow sensor.

 

 

Customer: replied 4 years ago.
ok going to look now... better question is can I spray starter fluid all around the intake after the MAF and listen for idle change?
Expert:  Amedee replied 4 years ago.
Sure.. you could do that... But when you spray it, If you have an air leak, it might not be as noticeable as one from behind the throttle plate (vacuum leak)... but you can sure try.
Expert:  Amedee replied 4 years ago.

Also, you can check the mass air flow sensor grams per second on your scan tool.

 

The specs at idle is 3.6-3.8 for manual transmission and 3.8-4.0 for automatic transmission. At 2500 RPM's no load the specification is 10.5-11.2 for manual transmission and 10.6-11.4 for automatic transmission. If the readings are low the mass air flow sensor is bad or you have a vacuum leak.

 

In addition, check the fuel trims when the vehicle is at idle and at 2500 rpm driving down the road. If the fuel trims are high at idle and normal while driving at about 2500 rpm, my money is on either a vacuum or an air leak after the mass air flow sensor.

Customer: replied 4 years ago.
I'll check all this Friday afternoon, headed out to jump on a plane for a business trip.
Expert:  Amedee replied 4 years ago.

Sounds good!

 

I will be looking forward to your reply!

 

 

Customer: replied 4 years ago.
ok this lame reader only allows me to capture and review freeze data when a code is generated i cant review realtime or history
Expert:  Amedee replied 4 years ago.

Thats ok.. if you get a chance to get a scanner that can read live data, we can go that route... if not, lets just check the intake tube/snorkel for cracks or rips.

 

If you have a voltmeter, you should be able to get a volt reading from the mass air flow sensor.

Customer: replied 4 years ago.

Air intake tube is stainless steel, no cracks that I could find, the coupler hose is a 4" hose about 6" long and it looks great as well. I did another visual inspection today of every vacuum hose on the car that I could get to and everything looks ok visually. How do I measure the MAF sensor while driving down the road at speed? Can you think of a method for a non mechanic (me) to leak test all this stuff??
Expert:  Amedee replied 4 years ago.

You should be able to take a reading from the mass air flow sensor at idle and while snapping the throttle while in park. You don't have to be driving to do this.

 

If the voltage is low at idle, chances are the mass air flow sensor is bad or you have a vacuum leak.

 

Also, if you can try and get your hands on a scanner that can read live data, that would be very helpful as well.



Edited by AMEDEE on 6/25/2010 at 2:57 AM EST
Expert:  Amedee replied 4 years ago.
Also, I know this was mentioned, but be sure to check the pcv hose/tubing. THis is very common on this engine causing this code. In addition, there is a TSB about the purge solenoid sticking open causing this lean code. You could check the purge solenoid (see if it holds vacuum) to be sure that it is not leaking fuel vapors from the evap system into the intake.

Edited by AMEDEE on 6/25/2010 at 3:06 AM EST
Customer: replied 4 years ago.
ok what wires do I need to be across the measure the MAF sensor? I will record the voltages at 1500 rpm and ??? Getting a scanner like that sounds good I will check around and see if anyone has one I can borrow. The one I got came from Advance auto for about $100
Expert:  Amedee replied 4 years ago.

Ok... sorry for the delay!

 

It is going to be either pin C or D. Here is an electrical diagram and a connector view of the mass air flow sensor.

 

graphic

graphic

Expert:  Amedee replied 4 years ago.

Here is the testing for the mass air flow sensor straight from the book.

 

MASS AIR FLOW (MAF) SENSOR INSPECTION

 


Visually inspect for the following on the MAF/IAT sensor.
Damage
Cracks
Bent terminals
Terminal rust
If any of the above are found, replace the MAF/IAT sensor. (See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION.)
graphic

MAF Rate and Load Value

NOTE: The scan tool shows the MAF rate and load value.

Circuit Open/Short Inspection

 

Disconnect the PCM connector (See PCM REMOVAL/INSTALLATION.)

graphic

 

Inspect the following harnesses for open or short circuit. (Continuity check).
Open circuit


MAF/IAT sensor terminal A (harness-side) and main relay terminal C (harness-side)
MAF/IAT sensor terminal B (harness-side) and PCM terminal 77 (harness-side)
MAF/IAT sensor terminal C (harness-side) and PCM terminal 88 (harness-side)
Short circuit


MAF/IAT sensor terminal A (harness-side) and body GND.
MAF/IAT sensor terminal B (harness-side) and power supply.
MAF/IAT sensor terminal C (harness-side) and power supply.
MAF/IAT sensor terminal C (harness-side) and body GND.

 

 

Expert:  Amedee replied 4 years ago.

Here are some more specs for your mass air flow sensor.

 

Key-On-Engine-Off Idle
0.0-0.2 V 0.60-0.90 V

 


MAF Volts Grams Per Second of Air Flow
0.34 V or 0.39 GPS
0.39 V or 0.95 GPS
0.50 V or 1.30 GPS
0.60-0.90 V or 1.69-4.50 GPS
1.00 V or 5.53 GPS
1.96 V or 22.92 GPS
3.90 V or 137.98 GPS

 


Typical Signal Values:
Compare Mass Air Flow To Voltage;

Engine Off;
- Key on engine off checks the zero air flow value, the voltage should be 0.0 to 0.2 volts. High sensor ground is the most likely cause of high signal voltage with the engine off.
- If the voltage is wrong check B+, engine ground and sensor ground.

 

Engine Running;
-Verify operation by comparing voltage to speed and MAF air flow values. These values vary with altitude and other operating conditions.

- If readings vary use voltage to air flow and 2 second wide open throttle test.

- Intake vacuum leaks will cause air flow values to be low because the air leak is not measured by the MAF sensor. Small leaks will show up more at idle than cruise because of the lower air flow at idle. Air leaks will cause long term fuel trim to be higher than normal.

Customer: replied 4 years ago.
Car is scheduled to go to dealer Tuesday for a $175 smoke test... yea.. ouch ! I'll let you know what I find out. I have printed out this entire thread for them to read in hopes they will check the MAF as well, etc.. to clear up this check engine light so I can get this dang car inspected. I have been stopped twice, ticketed one ($125 plu atty fees), now $250 NCDMV fine for car not passing inspection, been down countless days troubleshooting this.. what a nightmare
Expert:  Amedee replied 4 years ago.

I hear you loud and clear! Sometimes some vehicles can be very difficult to diagnose.

 

Lets keep our fingers crossed!

 

Please don't forget to hit the green accept button so that I may receive credit for the time that I have spent with you. In addition, bonuses and positive feedback are much appreciated!

 

Even after you accept one of my answers, we can still continue our conversation if needed.

 

REGARDS

 

AMEDEE

Customer: replied 4 years ago.

Car has been at the dealers for the last 3 days, now some $1,240 in Diag Fees later they can't figure it out. They want to fly in a specialist from Mazda to see if he will help. So I guess the saga continues.

 

What was done.

 

Replaced MAF

Replaced all hoses

Smoke checked, nothing found

replaced Cold Air Intake with factory box, etc...

 

I'm stumped....

 

 

Expert:  Amedee replied 4 years ago.

Sorry for the delay!

 

Was the mass air flow sensor replaced with a factory part? Maybe it is this simple? I see these things go bad all the time! I have seen bad mass air flow sensors right out of the box!

 

Also, just an idea.. be sure the exhaust is not plugged and that the valve timing is dead on. I don't think this is the problem because the vehicle has plenty of power... but working on cars, I have seen stranger things.



Edited by AMEDEE on 7/1/2010 at 12:59 PM EST
Expert:  Amedee replied 4 years ago.

Hello!

 

I am just checking up on you. What have we found with the vehicle?

Customer: replied 4 years ago.
Timing was dead on, replaced with a MAF on an identical 2004 same issue. Am spending $700 on factory OEM intake assy from bumper to intake to fix this.. I am thousands into this now, if this dosen't work you can buy this car really cheap !!
Expert:  david replied 4 years ago.
Hi I thought I would throw my 2 cents into the mix.

What happened when they put the stock air box on?

I have seen this many times when I install CAI in the newer model cars.

I hope this comes out right lol
You see with all the smog crap and the computer monitoring how much air the engine is getting (with the MAF) and how much air/fuel is in the exhaust (With the O2 sensors).
The stock air box and air tube are set up to deliver a set amount of air. Now the MAF sensor and computer are only able to read so much air flow. Its like a volume nob on a radio it will only go up so loud, The MAF sensor uses the same principle It will only send so much info to the computer. The stock computer can only see / understand so much info from the MAF.


Now with the CAI you are giving the engine more air then the MAF sensor can calculate (there is more air them what the computer thinks). So the O2 sensors are telling the computer there is a problem because there is to much air in the exhaust. Because the engine can only use so much air.

I have seen and done two things to fix this problem. This has worked for me and my customers, I am not saying it will work for you.

first and most easy is to get what is called an O2 Sensor Extender What this will do is move the O2 sensor up out of the flow of the exhaust. (Lowing what the sensor tells the computer)
graphic

Next and not so cheap is to get a power chip ether an Eadg or a Super chips. What this will do is remove the BS computer restrictions put in by at the factory.


On a side note If this works please just say thanks.
please do not accept my answer this is just what I would and have done to fix a the problem. Now do not listen to the dealership the dealer is a high priced parts changer.


Hope this helps
Good luck

Edited by david on 7/7/2010 at 6:04 AM EST

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