Codes P2177, P2187, P2097 – more data inside please help NEWBIE

[TJScanlon]

Hello folks

I am a brand new subscriber and trying to learn but drinking out of a fire hose right now so looking for a little guidance from you who have more experience.

2008 Mazda 6 iSport (2.3L 4 cyc) with 148k miles. Just purchased from my neighbor with my 16 yr old son as his first car. Neighbor was original owner and had car maintained mostly by dealer or independents. He doesn’t know cars but it had all basic maintenance done. We purchased for $1,200 – neighbor didn’t want to sell as he didn’t want to feel bad if something went wrong. I want stuff to go wrong a little as both my son and I are learning on this car:-).

We have done work on the car – new front brakes/rotors, repaired plastic bumper tabs, replaced headlights (they were yellowed and we couldn’t polish enough) and replaced the valve cover gasket (leaking oil) and plugs. I double checked the hoses we had to disconnect and they seem connected.

There really haven’t been drivability problems that I have experienced.

I was getting codes P2177, P2187 initially. I cleared a couple times and they came back and now am also getting codes P2097. All three codes are present.

My son and I removed the MAF sensor and cleaned that using MAF cleaner. It was dirty. The screws holding it into the top of air intake box are stripped so it is not tight. It seems secure but I can wiggle it a bit. I tried propane around it and other accessible areas to see if we could detect vacuum leak but I could not get a response.

Using BlueDriver live data on a warm engine parked.

At idle 750 RPM
STFT 25%
LTFT 0%
O2 0.965v

At 2000 and 3000 RPM
STFT 25%
LTFT. 0%
O2. 0.965v

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 flucuate
O2 goes from 0.965v to 0.8v back to 0.965v

I am too new to this and this is my first time making these measurements so I am not sure what I am really seeing. Having watched the video on Fuel Trim it appears my 02 sensors is maybe showing a rich condition? It also appears that the STFT is maxed out at 25% but it hasn’t reached equilibrium so the LTFT has not reset? I don’t know what this means as far as where to look.

There is a hose under the intake manifold which can be a problem on my generation of Mazda 6’s. To get at this hose (and I believe the PCV) requires removal of the intake manifold which is fairly involved (for me). I would love to tackle it but it is cold in Minnesota right now and was hoping this would be a spring-summer project:-). I ran propane over where the intake manifold is attached to the engine and could get no reaction.

My thought was vacuum leak but I can’t find anything obvious so maybe I am way off base.

I can get more measurements and have a multimeter. Would love to get some advice from everyone on where to dig.

Thanks,

Tom Scanlon
Minnesota

[Apex]

Hi Tom,

I replied to your intro post, but I posted a link to another forum with a suggestion on your MAF housing issue so I believe it has to wait for admin approval first.

It sounds like you are not dealing with a vacuum leak as typically in the case of a leak you will see a fuel trim improvement at higher RPMs. As for why the LTFT isn’t going anywhere, every manufacturer does their programming for when LTFT adjusts differently, so keep an eye on it, but in one case I believe Matt got burned on a reading where he only looked at the LTFT and the STFT was stuck lean or something to that effect, so it’s always important to look at both for a total fuel trim.

I had 3 suggestions for repair on my other post which I’ll repeat here for good measure if you wanted to fix the stripped screws, but the propane test was a good idea, assuming it would have fed enough to reduce the trim, did you try feeding a small amount of propane directly into the intake to see if it would show up on your fuel trims just as a sanity test? The first suggestion was what I linked to on a Mazda RX8 forum where they drilled out the plastic housing and used threaded inserts instead, you can google “DIY: Fix your MAF screw holes for $2.26” and the exact thread I was looking up will come up. I am assuming this will work on the Mazda 6 housing, but you will need to compare to what the 6’s housing looks like and see if this will work for you. My other suggestions were to either melt new plastic in there or use some sort of soft epoxy to fill in the hole, then carefully drill a new, straight hole and use your screws to cut into it.

You could have a lack of enough fuel or a bad reading from your MAF among some other possibilities, but a vacuum leak is actually unlikely in this case (or at least it is not the only contributor). Are there any drivability problems or just the lean condition? What do your MAF sensor readings look like on and off idle? Also, I would graph the O2 sensor signal to see if it is oscillating, it would be odd for it to be stuck at 0.9v when in a lean condition as that would indicate a rich condition or bad o2 sensor, unless you are looking at the rear o2 sensor anyway (B1S1 = Upstream, B1S2 = Downstream).

[TJScanlon]

Thanks Apex!

I am trying to get my head around all the readings, what they mean and how they relate. I had just watched Matt’s video where he talked about getting burned not looking at both STFT and LTFT – in it he had showed the O2 as high but noted that it should be low for Lean condition so my O2 was showing rich.

I will be looking at MAF readings tomorrow. The O2 sensor was B1S2, I have to believe my BlueDriver can read the B1S1 sensor but I must not of selected it during live reading. My BlueDriver OBD reader I am not sure reacts fast enough to see the oscillation in live setting. When I save the data is stores in Excel file and appears to take measurement every 0.5 seconds. As I get into this more I will need to look at a better diagnostic tool.

Really appreciate the lead on the MAF screw hole repair. The post hasn’t shown up yet but will check it out when it does – I was thinking the epoxy route but would like to check out the threaded insert before I go epoxy.

Thank you so much for taking the time to reply – I really appreciate the help!

Thanks
Tom

[TJScanlon]

For anyone following this. I don’t have an answer yet but did take some more readings with the BlueDriver. I am not sure how this will post below but here are the readings and the codes. 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

Short Term Fuel Trim Bank 1 (%) Engine RPM (rpm) Mass Air Flow Rate (lb/min) O2 Bank 1 – Sensor 2 – Oxygen Sensor Voltage (V) Wide Range O2S: Bank 1 – Sensor 1 – Current (mA) Long Term Fuel Trim Bank 1 (%)
25 731 0.4 0.965 6.449 0
25 884 0.6 0.97 6.449 0
25 1661 0.8 0.965 6.449 0
25 1860 0.8 0.965 6.449 0
25 1963 1.1 0.96 6.449 0
25 2329 1.5 0.961 6.449 0
25 2837 1.7 0.961 6.449 0
25 2733 1.5 0.957 6.449 0
25 3000 1.4 0.965 6.449 0
Consequetive 25 3030 1.5 0.965 6.449 0
Consequetive 18.7 2962 1.1 0.965 6.449 0
Consequetive 0 2517 0.7 0.953 6.449 0
Consequetive 0 2272 0.7 0.901 6.449 0
Consequetive 0 1719 0.7 0.476 6.449 0
Consequetive 0.1 1555 0.6 0.581 6.449 0
Consequetive 0 1375 0.7 0.86 6.449 0
Consequetive 0 1186 0.7 0.876 6.449 0
Consequetive 14.5 1120 0.7 0.9 6.449 0
Consequetive 25 1002 0.6 0.95 6.449 0
25 957 0.6 0.954 6.449 0
25 923 0.6 0.96 6.449 0
25 728 0.5 0.97 6.449 0

[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.

[Apex]

Hi Tom,

Trying to write this up to hit some of your questions before you get into replacing anything, unfortunately I don’t have much time at this very moment.

This is interesting because according to your new fuel trims, a -20% LTFT with a 0% STFT would indicate a rich condition, not a lean condition, yet you still have codes for lean condition?

I would not replace that O2 sensor without some confirmation it is bad. Remember that wideband sensors do not function like regular o2 sensors. See Matt’s video on wideband sensors on youtube. It may be bad since you’re not getting any change from the sensor even with propane, you MIGHT be onto something here, but I would make sure that it is bad since those sensors are quite pricey.

You will go into open loop on deceleration when you let off the throttle because the car is cutting fuel as the wheels are driving the engine (as opposed to the other way around).

Also, a CSV file is basically an table with data on it, there should be a way to convert this to a graph. I did a quick google and it looks like there are some online ways to do it.

[TJScanlon]

Thank you again Apex!

I did watch the video on Wide Band it was helpful. I did the WOT test yesterday and the B1S1 reacted similar to how the Toyota did in Matt’s video so now I am coming to the conclusion it may not be the A/F sensor. Unless there is a wiring issue that causes some intermittent issues – I am not familiar enough at all with the A/F sensors to know if they go bad is it binary, ie it is bad or it is good, or do they fail gradually?

I am going to clear the codes today to make sure I am not looking at old data now that the conditions have changed.

The one item that I haven’t been able to eliminate is the PCV and hose. It seems to be a common failure on the 2.3L Mazda. The unfortunate thing is it is under the intake manifold so I have to remove that to get at it. At this age and mileage, it is likely it has a leak or will have a leak. I really don’t want to do that until spring/summer:-).

I have a shop manual coming for this from eBay which hopefully will help. I am also going to download Forscan which is scanner software for Ford and Mazda and hopefully be able to get some better data.

I have downloaded the CSV’s into Excel and tried to graph but it was unsatisfactory. With the BlueDriver it looks to measure every 0.1 seconds for each measurement, so if I am tracking 5 PID’s it measure every 0.5 seconds. It doesn’t recommend more that 5 but I have done up to 7, but measurements every 0.7 seconds.

Thank you for taking the time to reply – I really appreciate it. I hope to post some more info today. I am also checking out info at scannerdanner which has also been helpful. Between Matt and Paul Danner I have learned a ton in the last 3 to 4 weeks. It doesn’t seem like it at the moment but if I look back to what I knew then, it isn’t even close.

Thanks,
Tom

[Apex]

Oh yeah, I forgot Forscan was good for some Mazdas as well. I wish I got to use it more, but unfortunately my laptop took a crap. Most of what I’ve worked on happen to be Fords.

Remember that a vacuum leak would show up as a lean condition (increased fuel trims) at low rpm, but improve at high rpm. Sometimes forum posts for a specific make and model can give you direction as an idea of where to start or what to look for with common issues, but they’re not the end all be all.

Also remember that sensor 2 should always show rich except if I remember right at WOT it will tend to follow or trail sensor 1. It is interesting the computer is throwing a code for a “too rich” condition on sensor 2.
You might wait for confirming the data with Forscan, but you could try running live data with only LTFT and STFT and seeing if you can get a reaction out of the propane into the intake.

Somehow we went from a very lean condition on and off idle to a rich condition on idle but not off of idle

[Apex]

Hi Tom,

I’ve been thinking about it again recently, and I recently watched a video that mentioned that a rear o2 sensor can actually affect fuel trims on Mazdas. I do vaguely remember reading or hearing (not sure if it was from Matt) that rear o2 sensors are not purely for emissions/confirmation of catalytic efficiency. The Rear O2 sensor did seem to have activity on your data, so I don’t think that’s necessarily the problem here, but it is actually a potential variable (one that I believe we have already eliminated).

One area I forgot to ask about in terms of data is calculated load and MAF readings, this is one area that I struggle in as I don’t know the typical readings you would get from a normally running engine, but perhaps we can find something here. What is your calculated load at idle with no accessories on, as well as free revving, and while driving? What is your idle G/s or LBs/Min readings?

[TJScanlon]

Apex

Thanks again for your help. I am learning so much…. but know so little:-).

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.

I wish I had a way to attach the graph as it may make more sense to others. Right now the car appears to be running without errors but the LTFT and the O2S1 seem off?

Thanks
Tom

[Apex]

Hi Tom,

New codes will not overwrite old ones, but if the conditions that set a CEL clear out they will likely clear themselves out if the conditions are no longer met. In this case we are no longer in a lean condition, we are in a rich condition, at least at idle.

So now we have a rich condition only at idle, the fuel trim may be just under the point where it will set a CEL. Is your STFT doing anything when you’re not at idle or are both at ~0%? I ask about the STFT because I believe that a reading of 6.45mA would be very lean, and -4.39 would be rich on deceleration, which I would think that on decel you would see a very lean condition (fuel cut).

What I was reading online is that the rear o2 sensor can be used to calibrate the front O2 sensor’s stoich reading, I have no idea if Mazda implements this in their ECM programming, but it is a possibility.

As for graphs, if you’re running forscan on a laptop you could always screenshot your data, or ideally just hit the save button after you stop live data, and you can save it either as a forscan graph or a csv.

I think we need to double check that total fuel trims as it seems like you’re running lean off idle and rich at idle which would make me think dirty MAF sensor… I’m a little suspicious that those MAF readings may be off. Did you ever check your calculated load %? I would like to see that data as well at idle with no accessories on (car warmed up). I assume when you cleaned the MAF you cleaned the 2 very small elements at the top of the sensor?

[TJScanlon]

Hello all,

Thanks to all that have helped with my 2008 Mazda 6 2.3L. Wanted to post a quick update to this. The primary o2 wide band sensor was bad. I am not sure if it was completely Kaput when I first started this but by the end it was. I don’t recall checking at the beginning of my educational odyssey learning about this, but at the end I checked and the fuel loop status and it was Open. It never went into Closed Loop. I didn’t know enough to check that at the start of this but learned as I went along. I assumed that when the engine warmed up and idle dropped that indicated it was in closed loop but I was wrong.

I had to remove the cat to get enough access to the primary o2 sensor to remove it. Decided to replace the secondary o2 sensor at the same time while I had the cat off as it was original with 150k on it. The gasket I got from auto store is wrong and I have an exhaust leak but the system goes into closed loop and responds as it should. Received the correct gasket today and will be replacing this weekend. I have a stuck exhaust manifold spring stud that I need to get out as well so I don’t have to pry the cat off it. Hoping heat, PB Blaster, wax and a stud removal tool will be successful. I don’t want to make this harder than it should be:-).

Then I need to chase down an oil leak and figure out what I need to do to correct that. I now officially have more in tools than I do in the car but am having a blast learning and doing this.

Anyway – wanted to post in case someone searched this in the future.

Thanks,
Tom Scanlon

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