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Fixed - Mostly:-) 2008 Mazda 6 2.3L P2177 P2187 P2097 - Lean and Rich?

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3 years 2 months ago #45952 by tjscanlon
I am new to the forum and a newbie trying to learn troubleshooting. This is my 16yo's first car that we are working on and having fun. It has 149k miles on it - bought from neighbor who was original owner and had maintained. This is my first foray into digging into engine control and trying to troubleshoot and I it is like drinking from a firehose:-).

It has not suffered drivability issues yet, just throwing the CEL.

The freeze frame showed the P2177 tripped the CEL and it occurred while driving around 2000rpm and 35-50mph (I cleared it once it freeze frame showed P2177 while driving both times).

I have inspected air intake hose and it looks solid. Have cleaned the MAF. We replaced valve cover gasket as it was leaking oil and replaced spark plugs at same time (I don't think related but wanted to note it).

I have tried using propane to see if I could detect vacuum leak but could see no changes but I can't get at the PCV or hose under the intake manifold


I am not sure how this will post below but am attaching the readings and the codes. I took out some lines for brevity and where I labeled consequetive is sequential as the STFT changed there - each line in that section is 0.5 second apart as near as I can tell from BlueDriver. From Left most column is STFT which is pretty well stuck at +25% at idle, 2000 rpm, 3000 rpm. It drops to 0% when I let off the gas but quickly returns to +25%. The LTFT has never moved from 0% and this is over the last couple weeks. The car hasn’t been driven a ton but probably 20-30 miles.

I am very new at this and trying to digest this. So it looks like the system is maxing out the STFT at +25% (which seems low as max?) which is lean, the O2B1S2 is showing rich. It appears that the system can’t hit stoichometry and the STFT is trying to adjust but is maxed out but because the O2 sensor never gets to equilibrium the LTFT never adjusts to +25%.

I could not detect any vacuum leaks but there areas I can’t see or get at easily under the intake manifold.

My BlueDriver does not show waveforms so I can’t see if the O2 sensor oscillates properly.

I am just not understanding how I can have lean condition on the STFT and a rich reading on the O2 sensor and the LTFT stays at 0.

Thoughts on what to check next?

So the numbers from Left to Right are STFT, RPM, MAF, O2B1S2(V), O2B1S1(mA), LTFT

P2177 System Too Lean off Idle Bank 1
P2187 System Too Lean at Idle Bank 1
P2097 Post Catalyst Fuel Trim Systerm Too Rich Bank 1

Thanks
Tom Scanlon
Minnesota
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3 years 2 months ago - 3 years 2 months ago #45970 by Wightscope
My take on this is that your (apparently malfunctioning) upstream wideband sensor at +6.6ma is indicating a very lean condition - consequently fuel trims are pegged +ve, except on the over-run where fuel is shut off so there are no fuel trims.
As the upstream sensor is lying, then the mixture is too rich due to the fuel trims - as evidenced by the downstream sensor saying so.
I do not think your scan s/w is reading the LTFT correctly.

The upstream wb O2 sensor may be missing it's heater feed, someone that knows these wideband sensors may be able to tell the failure mode from the amperage shown. Though it would be most helpful if your scanner showed a (converted) Lambda value for the upstream sensor just to make life easy !
Last edit: 3 years 2 months ago by Wightscope.

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3 years 2 months ago #45972 by tjscanlon
Thank You Wightscope.

I was able to get the WBO2 in lambda - stuck at 1.9. I am attaching live data showing that from a warm car at idle up to 3k rpm.

I also looked into Mode 6 on the BlueDriver. From what I can tell it does some self testing of some of the emission components and the WBO2 sensor B1S1 could not complete its test. I am also attaching that test.

The more I look at this, the more it points to that WBO2 B1S1. I am not 100% confident of that as I have been trying to learn this stuff over the last week or two and have just scratched the surface.

If anyone has other thoughts on how to confirm this or disprove it, I would really appreciate it.

There are no drivability issues at this point.
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3 years 2 months ago - 3 years 2 months ago #46003 by Wightscope
I am pretty sure the B1S1 is the issue, the question is why.
You can add extra fuel and see if you can drive it rich (propane/brake cleaner etc in the intake) - but looking at the output I doubt it.
Whilst you don't have a heater code (or a dead sensor code for that matter) you should check for voltage on the heater wires at the sensor (usually the 2 wires the same colour, though it may be modulated, in which case they may be different colours!), and check the resistance of the heater in the sensor you will need to find the value but I suspect around 2-10ohms
I would say use a test light on the heater wires - but a wrong connection could be very expensive unless you are certain of the wires so I would not recommend it.

You will need to look at the spec/data sheet for the sensor you have to see what the other wires should be it could be a 4 or 5 wire unit and check the integrity from PCM to the sensor, and the ground wire if there is one.
Basically you need to eliminate the feeds and wires before calling a bad sensor.

Oh and if you drive it for long in this rich condition you will destroy the CAT.
Last edit: 3 years 2 months ago by Wightscope.

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3 years 2 months ago #46027 by tjscanlon
Ugh - the numbers changed and now I am not sure what is happening. I am kind of using this to think out loud and learn. So I think we have not driven the car enough trying to troubleshoot. The STFT was stuck pretty much at +25% and didn’t change whether at idle or while driving unless I took my foot of the gas. The LTFT never moved from 0. Now I am thinking I finally drove the car enough for the LTFT to reset. It is now running at -0.20% at idle and the STFT is at 0. Now if I accelerate or raise the RPM the LTFT goes to 0. The STFT doesn’t change and stays at 0. So I pulled out the propane again tonight to look for a vacuum leak but could detect no change in RPM or STFT or LTFT at idle. I opened the air filter box and put the propane in the intake - no change. It still appears that the precat wide band O2 sensor is not changing much and the post cat looks to be running fairly rich (higher voltage).

So it could still be the pre cat O2 sensor and the only thing that changed was the LTFT reset. The thing that throws me off is that it now fluctuates with the RPM and goes to 0 at higher RPM which may indicate vacuum leak although I would think the STFT would fluctuate as well.

I tried order service manual so I could look at the Wide Band O2 sensor wiring,

File Attachment:

File Name: 2008Mazda6...8-21.pdf
File Size:811 KB
but of course that didn’t download as a PDF so am waiting for a reply back from the company to try the download again. Nothing can be easy:-)

I am attaching a PDF of latest measurements.

To anyone following - would appreciate any thoughts.

Thanks
Tom

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3 years 2 months ago - 3 years 2 months ago #46030 by Wightscope
Weird things going on here. Earlier post your WBO2 was 6.449ma = lambda 1.9, now 6.466 = lambda 1.01
Now LTFT is changing in a second from -20% to almost zero with no change in STFT or rpm.
Have you got a different scan tool as maybe that makes sense to someone else but not me!

Ignoring that I still think B1S1 is not working
Last edit: 3 years 2 months ago by Wightscope.

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3 years 2 months ago #46068 by tjscanlon
Updating with history into one message
Ok – now things have changed and I am really struggling to figure this out. So originally had CEL and these three codes. I am summarizing where I started and where I am at – sorry for the novel but documenting this helps me try to make sense as well. As always – thanks to all for any suggestions. I hope to be in a position someday where I can help some other newbie!
Before these codes I changed valve cover gasket (lots of oil leak into spark plug wells and side of engine) and replaced spark plugs at that time. The codes did not occur right after this so I am not sure there is any connection but wanted to share it. After codes showed up, I cleaned MAF with MAF cleaner – did look quite dirty and now is cleaner. It did not fix the CEL or codes.
2008 Mazda 6 i4 2.3L 149k
P2177 System Too Lean off Idle Bank 1
P2187 System Too Lean at Idle Bank 1
P2097 Post Catalyst Fuel Trim System Too Rich Bank 1
Using BlueDriver live data on a warm engine parked.
At idle 750 RPM
STFT 25%
LTFT 0%
O2B1S2 0.965v
Wide Range O2 B1S1 6.449 mA
At 2000 and 3000 RPM
STFT 25%
LTFT. 0%
O2. 0.965v
Wide Range O2 B1S1 6.449 mA

When taking foot off accelerator within 3 seconds
STFT 25% to 0% and then back to 25% within 3 seconds
LTFT 0% this does not fluctuate
O2 B1S2 (downstream) goes from 0.965v to 0.8v back to 0.965v
Wide Range O2 B1S1 6.449 mA

I tried using propane to see if I could detect a vacuum leak or induce a change but detected no change no matter where I placed the propane.
Freeze Frame showed the P2177 triggered the CEL and it occurred while driving around 2000rpm and 35-50mph (I cleared it and checked again).
So fundamentally the Wide Range O2 B1S1 did not change with RPM nor did the STFT or LTFT?
During this time I have not driven the car much – probably less than 20 to 30 miles as it is my 16 year olds car that we are working on and with the pandemic, just hasn’t been much need to drive.
Now the readings just changed. I suspect this is because we have driven the car enough to reset the LTFT. It is now set at -20%. Here are the changes with a new pending code – P2188 System Too Rich at Idle Bank 1.

Confirmed Codes:
P2177 System Too Lean off Idle Bank 1
P2187 System Too Lean at Idle Bank 1
P2097 Post Catalyst Fuel Trim System Too Rich Bank 1
Pending Code:
P2188 System Too Rich at Idle Bank 1
Measurements now from BlueDriver (every 0.7 seconds):
Idle 750 rpm
STFT 0%
LTFT -20.3%
O2 B1S1 Equiv Ratio 1.010
O2 B1S1 mA 6.461
O2 B1S2 V Started 0 – went to 0.945 after about 60 seconds for 10 seconds, then went to 0.015v for about 20 seconds then stayed at 0.880-0.965v for last 2 minutes of measurements?
Commanded Equiv Ratio 1.008

2000 rpm
STFT 0%
LTFT -0.0%
O2 B1S1 Equiv Ratio 1.010
O2 B1S1 mA 6.461
O2 B1S2 V 0.965v
Commanded Equiv Ratio 1.001

So like I mentioned – it appears that finally drove enough to reset the LTFT to -20.3. The O2B1S1 mA doesn’t change at all with RPM. The LTFT goes from -20.3 to 0 with increase in RPM. The STFT does not change at all with RPM.
Before the LTFT reset to -20.3. The STFT was always at 25 and LTFT was at 0. These did not change at all with RPM, except for the short blip when foot came off the gas and STFT went from 25 to 0 for a couple seconds (open loop?) then went right back to 25.
I tried propane again around intake manifold, vacuum lines and even open the air filter box and sent it right in the intake and it seemed to make ZERO difference.
Using Mode6 on the Blue Driver
O2 Sensor B1S1: Test did not complete.
O2 Sensor B1S2: completed and passed.
EVAP Monitor (0.040” and 0.090”) Test: did not complete (I have not checked this)
Purge Flow Monitor Test: did not complete

I will need to get a better scanner that allows graphing (the BlueDriver does but it doesn’t measure fast enough and doesn’t save the graphs – it saves the values in a CSV. I think it is a nice little $99 Bluetooth OBDII but as I am getting into this more, I will need a better scan tool).
I don’t want to be a parts changer but I am getting to the point where I am thinking of putting in a new Wide Range O2 Sensor. I am trying to learn this but I am super busy with work and I want to start eliminating potential sources and issues. From what I have read – the Wide Range O2 (AF) sensors have about a 150k mile expected life and I am right at that point.
I am really kind of impressed with what I have learned over the last 2 to 3 weeks but it is clear that this takes time to sink in. The other mitigating factor is it is COLD in Minnesota right now which makes it hard to get excited about working on my sons car. This is practice for me for when I buy my used Miata.

Thanks
Tom

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3 years 2 months ago #46074 by Matt T

tjscanlon wrote: During this time I have not driven the car much – probably less than 20 to 30 miles as it is my 16 year olds car that we are working on and with the pandemic, just hasn’t been much need to drive.
Now the readings just changed. I suspect this is because we have driven the car enough to reset the LTFT. It is now set at -20%. Here are the changes with a new pending code – P2188 System Too Rich at Idle Bank 1.


Did you put gas in the car driving the car around "enough"? Something changed and I'm wondering if it was the fuel....

tjscanlon wrote: I will need to get a better scanner that allows graphing (the BlueDriver does but it doesn’t measure fast enough and doesn’t save the graphs – it saves the values in a CSV. I think it is a nice little $99 Bluetooth OBDII but as I am getting into this more, I will need a better scan tool).


You can graph CSV files with a spreadsheet program. Or sign up for scanshare and try it. Another thing I'll do on the phone is screen shot the graphs.

www.scanshare.io/

Regards a scan tool you could get into Forscan for less than the price of that bluedriver if you have a laptop. That'll give you basically O.E. level coverage for Mazda, and any Ford products you might have. If you're also working on other makes I'd recommend getting an OBDLink MX+. It has O.E. codes and PIDs for some other makes free in the phone apps.

forscan.org/forum/viewtopic.php?t=6142

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3 years 2 months ago #46075 by tjscanlon
Thanks Matt,

No gas change unfortunately. I think but am not sure, that it was simply time or mileage based and the LTFT learned the new normal.

Thank you for the tips on Scanshare - will check it out. I tried some graphing in Excel but it wasn't as helpful as I thought. It looks like the BlueDriver only measures every 0.7 seconds when I am live logging 6 or 7 measurements. It looks like every 0.5 seconds when measuring 5 or less.

Forscan may be the ticket. I used to drive Audi's and used VAG-COM on laptop for those. However, I was never this deep into diagnostics at that time so I think I really under utilized that software:-). Forscan seems pretty similar in how it operates.

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3 years 2 months ago #46252 by Eicca
I replied to your comment in my thread about my Lexus and a similar issue. Short version: I’m suspecting corrosion or weak contact in the MAF sensor plug.

Just don’t go putting anything but Deoxit in that connection or it’ll really mess it up.

1998 Lexus GS400 V8

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3 years 1 month ago #46354 by tjscanlon
So here is where I am at. I started thinking about the codes more and realized I don’t understand how or when they are stored. Once the CEL comes on, do new codes over write what was there before? I don’t know but the more I thought about it, I thought maybe not and perhaps I am looking at old data? In trying the propane (which I am still not sure if my flow was enough – I was using a torch nozzle and could hear and smell it but maybe the flow wasn’t enough to impact engine?) In any case, in using that I was lifting the air box which stresses the MAF cable which I will get to in a second. I then decided to clear the codes which I had not done for awhile. This was last weekend. I have driven the car about 30 mile s since then and it has been on about 10 short trips. So it has been cycled on and off 10 times. I have no codes or pending codes. LTFT is still running -20.3%.

I have since gotten Forscan and the live scanning/graphing is superior than BlueDriver. BlueDriver is a little easier for a novice to use though. I have also gotten the Factory Service Manual for the 2008 Mazda 6 and that has a ton of data and expected values.

So here is where I am at. CEL is still off after clearing and driving 30 miles. I have no codes. I have no pending codes. My LTFT is still running -20.3% at idle but goes to 0 upon acceleration and pretty much stays there while driving.

According to the factory manual the O2S1 should measure 0.0 mA while driving at 3000 rpm and when take foot off the gas it should jump up to 0.25mA. Mine seems to read a steady 6.45 mA while driving and drops to -4.39mA when foot comes off accelerator.

MAF looks to be at about 2.4 g/s at idle and and went up to about 60 g/s at 3300rpm. It seems to track well with RPM.

I don’t know if when I was moving the air intake box around trying to shoot the propane if I made made the MAF connection better. I have just used electrical cleaner on those connections.

So – no CEL, LTFT at -20.3%, O2S1 seems to have a weird reading at 6.45mA when from what I can tell from manual it should be around 0. Maybe I just have to have son drive it until CEL shows up again but it is bugging me.

I have attached a PDF of what I graphed to see if it makes sense to anyone else

Thanks
Tom
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3 years 1 month ago #46360 by Tyler
Trying to catch up with this thread. :silly: Forgive me if I repeat anything or miss a test result.

Would you mind grabbing another capture with Forscan? RPM, vehicle speed, STFT, LTFT, RO2FT, upstream A/F current, downstream voltage, and whatever Mazda uses for a Loop Status PID. I'm interested in the Loop because I'm not sure if the A/F current PID can be relied on if the Loop is anything other than Closed.

In other words, if you're driving around in Open Loop Fault, the upstream A/F PID may not be telling anywhere close to the truth. :lol: Despite the lack of codes, the PCM may still be seeing something about the A/F sensor behavior it doesn't like, and just hasn't coded yet.

If the 6mA upstream and .9V downstream readings are right, then I'd be suspicious of a lying upstream sensor. If your AFR/lambda was truly that lean, you'd have a hard time getting out of your own way. :lol: .9V downstream suggests you've got plenty of fuel. Since you're not complaining about a lack of power, that's the sensor I'm gonna believe.

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3 years 1 month ago - 3 years 1 month ago #46365 by Hardtopdr2
definately graph the o2 sensor readings this sounds like a stuck rich rear o2 sensor to me.

File Attachment:

File Name: mazda6mode6.pdf
File Size:118 KB
Last edit: 3 years 1 month ago by Hardtopdr2.

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3 years 1 month ago #46963 by tjscanlon
Ok guys - been really busy with work and we have been in a deep freeze here in MN (and apparently everywhere else) so I have had a chance to get back to this until now.I feel somewhat or a lot like an idiot. I always assumed it was going into closed loop as when the car warmed up, the idle lowered to what I would expect to be normal. However - I never actually checked it. I am so new to this, I never even thought to check it! I really need to develop better trouble shooting techniques. The first is to capture a comprehensive base line to work from. Now to be fair, when I started this I didn't have Forscan to capture all of this. That being said, I am not sure really where I started on this.I have no codes and the only thing off is the LTFT is -20%, but the car isn't running in closed loop. As you can see from the two attached graphs it is Open Loop at idle and while driving. It showed Open Loop almost the whole time when driving but for a few seconds it show OL-Drive, which I think means about the same thing but am unsure.So based on what I am seeing with the AF sensor showing 6.45mA and not moving and the system in Open Loop. My suspicion is that I have a bad AF Sensor that isn't providing a logical signal to the ECM and prevents it from going into closed loop. I would think it would throw a code but I don't know enough to know if that is true or not.Thoughts?ThanksTom
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3 years 1 month ago #46995 by 70monte
If you are staying in open loop the entire time, your STFT is not being used since it's only being used in closed loop. The #1 job of the LTFT is to keep the STFT as close to 0% as possible. The #1 job of the STFT is to keep the o2 sensor as near to stoichiometric as possible which will be impossible if you are always in open loop.

According to Paul's Engine Performance Diagnostics manual, A forced open loop condition will occur when an O2 sensor will not respond to the computer's command. It says that it will set a trouble code when this happens which you say you don't currently have.

I'm not sure you can trust the LTFT numbers given that the STFT's are not being used in open loop.

Not sure if any of this info is helpful but just throwing it out there.

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3 years 1 month ago #47022 by tjscanlon
Thanks 70Monte - it all helps at this point:-) I hope to get a little breather with work and we have a little warmer weather to get under and check the connection to the AF sensor.

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3 years 4 days ago #47689 by tjscanlon
Hello gang,

Just wanted to come back and update this post in case anyone was following or finds it in future because it lines up with problems they are experiencing. Thank you all for the help during this. It took me awhile to get back to working on this and nothing has been easy. If there is a rust free bolt on this car - I'll be damned if I can find it:-)

After testing for awhile and trying to make sense - everything kept pointing to the primary o2 sensor. I never got a good reading from that. A special thanks to Tyler for pointing me to check the loop status. I could have sworn I did that early in this process but I can't find any saved readings where I did so I think I just assumed it went to closed loop when the RPM's dropped. I checked it and it was in Open Loop. At that point - I decided I had enough evidence to replace the primary o2 sensor.

I could not get that thing out of course, so I decided to remove the cat so it was easy to get access to. At that point decided to replace the post cat sensor as well as the car has 150k on it. Couldn't get one of the manifold studs out so had to push on the rubber hangers to get it off the stud. Got it out. The sensors were easy to replace then. Had new gaskets and put them on and replaced cat. Really had a problem getting it back in over the manifold spring stud but ultimately did. Hooked everything up and took it for a drive. Went right into closed loop and I saw good readings on the primary o2 sensor and everything else.

The problem is I think I have an exhaust leak - I think in trying to reattach the cat and get it over the spring stud - I knocked off the donut gasket. I need to get that resolved but overall am really pleased on the outcome of the new sensors.

I am looking into getting a Quick Jack to make it easier for this old guy to get under the car. Anyone have one and what do you think?

Thanks again for all of you who took the time to read my novels and respond - it is much appreciated.

Thanks
Tom Scanlon

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3 years 4 days ago #47705 by Tyler
Glad to hear it's mostly fixed! :lol:

Your scan data reminded me of an '07 CX-7 that came in with broken chains and got a long block. After getting it running, I found the upstream A/F stuck just like yours. Full time Open Loop. I figure maybe it just needs a trip down the block? Nope. Well, maybe it needs the battery cables disconnected. Still nope. :silly:

Stupid A/F sensor was $300 our cost at the time. Shop owner was not thrilled when I gave him the bad news. :lol:

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