System too lean error codes

[james250]

Finally going to get round to changing the O2 sensors over the Christmas Break. I ended up getting 2 Denso ones that have Chinese writing on the box. I believe they are Chinese replicas with Denso packaging LOL. I paid with delivery around £180 for the pair. Here is a pic:

 

I didn't know which o2 22mm socket to get, the offset one or normal deep one. So I bought both as I don't want to be stranded in the middle of the job during holiday season. Pics of the sockets below, are they correct?

 

 

In terms of a long bar to act as a breaker bar, any ideas where I can get some sort of bar that can slot over an existing wrench?

Also, @normski2 you mentioned in your PCV replacement guide to use a bit of threadlock. I assume something like LocTite that is used on the bolts of the water pump etc? 

[Texas]

If you want a 'bar' to extend your socket wrench then you could try to find a 'friendly' looking scaffolder!!! And bung him a few beer tokens for a two/three foot bit of scaffold tube. Could come in useful for other jobs as well.

Paul m.

[normski2]

I just used a piece of pipe over the handle of my socket wrench and that gave me the added leverage. They are very tight to move ...... and then suddenly spin loose.....so mind those fingers.

Either socket will do the job. The direct type will be the one particularly for the downstream sensors. They are located on the exhaust piping right under your seat ... so to speak!

Bank 1 Sensor 1 is dead easy and will likely take 15 mins. Any longer will be the grunt required to loosen the old one.

Bank 2 Sensor 1 is a bit of a pig. It is well and truly obstructed. You will have to remove the Battery and the trays and electrics below it. This will give you the access you need but its still pretty awkward pushing the plug connector home as it sits at the back of the block. Read both Noobie and my accounts that should give you all the insights you need. I seem to recall it took me about 3-4 hours to do both sensors. Bank 2 Sensor 1 was a toad to undo. I must have grunted for nigh on 15-20 minutes just getting the damned thing to loosen. Give both a squirt or 5 of WD40 or Plusgas etc etc for a couple of days before you plan to do them. Hopefully it may just get into the threads a bit.

Loctite is fine for the threads on the PCV valve. You will have the room to get at the PCV when you are doing Bank 2 Sensor 1. So do it at the same time.

There should be a small tube of copper grease in with the sensor. If not, you will need a smidge on the lower threaded portion to prevent seizing of the threads. That little plastic shield protects the sealing compound at the head of the threads ...its a bit like a sticky, grey-coloured mastic.

[johnatg]

3 hours ago, james250 said:

Finally going to get round to changing the O2 sensors over the Christmas Break. I ended up getting 2 Denso ones that have Chinese writing on the box. I believe they are Chinese replicas with Denso packaging LOL. I paid with delivery around £180 for the pair. Here is a pic:

 

@normski2

That writing is Japanese, not Chinese. They're most likely genuine Denso ones.

 

[james250]

21 minutes ago, johnatg said:

That writing is Japanese, not Chinese. They're most likely genuine Denso ones.

 

Oh LOL, ooops. Thanks. If it's Japanese then chances are these are Genuine Denso then.

[LennyLexus]

Hi James, 

Did you get the sensors from RockAuto? 

Have you also tried cleaning your maf sensor? 

Did you have any faults prior to the P0171 and P0174 codes?

[james250]

4 minutes ago, LennyLexus said:

Hi James, 

Did you get the sensors from RockAuto? 

Have you also tried cleaning your maf sensor? 

Did you have any faults prior to the P0171 and P0174 codes?

I ordered the Sensors from the famous auction site from a seller in the US. I was ordering it from RockAuto but then with delivery and Taxes it was working out to quite a bit. So ended up getting it from eBay. I'm hoping they are Genuine but you never know with these auction sites. My MAF sensor is fairly new as I replaced it as a preventative measure only a year before that. It's been a good few months since the error codes, but I get the feeling it was to do with the fuel i put it. When I went on holiday up North, the closest petrol station I was able to find was Morisons and not long after that my problems started. I cleared the codes as I carry the OBD tool. But came back after X amount of miles. Eventually when I got home and after a few re-fills of normal shell fuel the error hasn't returned. However, I will still change the sensors as they are way overdue.

[LennyLexus]

I do hope they are genuine! I've ordered 234-4521 from RockAuto for around £100 before UK VAT and import duty. The other sensors I'll be looking to get from buycarparts based in Germany, same price as rock but no VAT and import duty ~£165. 

Did you get a Denso maf too? If so, where from and how much was it? 

I'd be surprised if my lean codes from bad fuel, as I'm mostly use BP/Shell 95Ron topped up with Archoil AR6900P. My codes pop up while stationary and the car is at operating temperature.. I'm suffering from a 10-20% drop in mpg and a very smokey exhaust, however engine is still silky smooth with no loss of power (that I can feel).. My daily commute it is pretty all stop start traffic. 

[james250]

OK so today I replaced both o2 sensors and the PCV valve. Let the car idle for a little while. I used plus gas to help release the sensors. After running it there was a lot of smoke burning the residue of plus gas away. Eventually it stopped but smell is there a little still. So about 25mins after letter it idle. I took it for a spin about 30min drive. Parked up did some shopping. The car drove much better and the response was great. So i was thinking wow something has made a difference. I can actually feel the difference. So then I needed fuel so only option was tesco, so i filled 15L of super unleaded. Driving home it drove nicely til right at the end the dreaded engine management light came back on. Argghhhhhhhh. Damnnnnnn!!!!! So plugged in the scanner this time it read:

Stored Codes:
P2195 - O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor 1

Pending Codes:
P2195 - O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor 1
P2197 - O2 Sensor Signal Biased/Stuck Lean Bank 2 Sensor 1

So I decided to clear the codes while the car is running. Then click read codes again and almost immediately there is 2 pending codes. But the pending codes are:

P0171: System Too Lean Bank 1
P0174: System Too Lean Bank 2

I have no idea what is going on, any help guys? getting really frustrated now. Why is the new pending codes different to the previous pending and stored codes?

[james250]

OK here's an update. This morning had to get my MOT done. I was thinking it can't be the sensors, they are new. Plus the car drove silky smooth compared to usual. So I decided to just tighten the oxygen sensor on Bank 1 a little. It moved about a few millimetres. Not sure if that would have made a difference. Then decided to check the air intake and noticed that the breather hose from the motor to the intake tube wasnt tight it popped out quite easily. So I tightened this. Then I disconnected the Battery again for about 30mins and let the car re-adjust just before the MOT. Took it in for MOT and it passed and no concerns on the Emissions. I was worried that the check engine light would come on during the MOT test. They had the car running for almost 45mins. 

So I drove home, by this time I thought surely a code will turn up in the pending codes if there was something wrong, still nothing showed up. Later went to the cinema which was about a 10mile drive. Parked for about 2hrs then when I went back to the car plugged in to read the codes to see if there is anything pending. I am checking for pending codes because as far as I understand it starts of as a pending code and then turns into a stored code if it remains on the ECU. So this time 1 pending code showed up and it was the: P2195 - O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor 1

So now I am thinking: damn the hose issue didnt fix the problem. So nevertheless it's still pending so I thought I would see if it turns into a stored code. Drove home and then turned car off and went back to it few mins later to check if any other pending codes have registered. This time there was 0 pending codes. Question is what on earth happened to the other pending code? 

[is200 Newbie]

7 hours ago, james250 said:

OK here's an update. This morning had to get my MOT done. I was thinking it can't be the sensors, they are new. Plus the car drove silky smooth compared to usual. So I decided to just tighten the oxygen sensor on Bank 1 a little. It moved about a few millimetres. Not sure if that would have made a difference. Then decided to check the air intake and noticed that the breather hose from the motor to the intake tube wasnt tight it popped out quite easily. So I tightened this. Then I disconnected the battery again for about 30mins and let the car re-adjust just before the MOT. Took it in for MOT and it passed and no concerns on the Emissions. I was worried that the check engine light would come on during the MOT test. They had the car running for almost 45mins. 

So I drove home, by this time I thought surely a code will turn up in the pending codes if there was something wrong, still nothing showed up. Later went to the cinema which was about a 10mile drive. Parked for about 2hrs then when I went back to the car plugged in to read the codes to see if there is anything pending. I am checking for pending codes because as far as I understand it starts of as a pending code and then turns into a stored code if it remains on the ECU. So this time 1 pending code showed up and it was the: P2195 - O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor 1

So now I am thinking: damn the hose issue didnt fix the problem. So nevertheless it's still pending so I thought I would see if it turns into a stored code. Drove home and then turned car off and went back to it few mins later to check if any other pending codes have registered. This time there was 0 pending codes. Question is what on earth happened to the other pending code? 

It could have been dirt on the sensor when replaced - oil film or coming into contact with dirt when replacing the sensor? Did you replace both or just the one sensor?

Keep an eye on it though as it could be (not saying it is) a copied sensor as you said it had Japanese writing on the box from a US eBay supplier

[james250]

So the CEL has come on again. This time the stored code is P0171 - System Too Lean Bank 1.

There is also pending code for Bank 2 and also pending P2195 - O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor.

I replaced both sensors. The sensors do look really genuine they had denso and numbers etched on it too.

Strange thing is it all started with errors relating to bank 2. But now more errors seem bank 1 related. I'm wondering if I have a vacuum leak somewhere. If I have vacuum leak shouldn't it effect performance? Is there a way to test for vacuum leaks? Could it be PCV valve hose? I reused the same clip

[james250]

Any tips anyone? It's becoming a right pain now 

[steve2006]

I think you can have a “smoke test” done at a garage, this device produces smoke that is then pumped through the engine intake, any induction leaks are then easily spotted if the smoke comes out in that area.

Another method would be live data monitoring using the correct diagnostic equipment.

[is200 Newbie]

On ‎23‎/‎12‎/‎2017 at 11:06 PM, james250 said:

So the CEL has come on again. This time the stored code is P0171 - System Too Lean Bank 1.

There is also pending code for Bank 2 and also pending P2195 - O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor.

Sorry - I did answer this but have had issues with posting to the forum for some reason...

Best place to start is to reset the codes using an ODBII reader - it will give you a place to start - if the replaced sensors have had any protective film on them then through use it would have burnt off by now (through use) - possible that the stored codes are still showing.

On ‎23‎/‎12‎/‎2017 at 11:06 PM, james250 said:

I replaced both sensors. The sensors do look really genuine they had denso and numbers etched on it too

Do you still have the "good" old sensor - you said before one had failed but you have replaced both - you could retrace your steps in replacing one of the new sensors with the known good one - its a bit of a faff but will prove the new sensors are good. It will give you the opportunity to re-check all the connections that were removed during the original install also.

 

On ‎23‎/‎12‎/‎2017 at 11:06 PM, james250 said:

Strange thing is it all started with errors relating to bank 2. But now more errors seem bank 1 related. I'm wondering if I have a vacuum leak somewhere. If I have vacuum leak shouldn't it effect performance? Is there a way to test for vacuum leaks? Could it be PCV valve hose? I reused the same clip

It would need to be a big vacuum leak to effect performance - pipe come off for instance. you MAY? hear a whistle or air escaping when the engine is running if theres a leak. A re-used clip should not give you any issue unless it was damaged / stretched when removing or replacing the hose back.

Make a not of the existing codes and then reset the system and see what errors come up ... - it would not have passed the MOT if the emissions were high so its going to be something easy? to find/repair

[james250]

Thanks @is200 Newbie 

I do have a old sensors, I was going to try putting one of the old ones back into bank 1 but then today the codes caused the CEL to come back on and this time it reads:

Stored:
P2197 - O2 Sensor Signal Biased/Stuck Lean Bank 2 Sensor 1 

Pending:
P2197 - O2 Sensor Signal Biased/Stuck Lean Bank 2 Sensor 1 

This makes me believe it is not the sensors because it's randomly giving errors either the one above related to Bank 1 or 2 or System Too Lean error. This leads me to believe it's not the sensors after all.

[james250]

Can someone if they have access to their latest emission test results give me their results so I can see if mine was close or way off.

[iwonder]

Check manifolds for pinholes or intake plenum seals.

[johnatg]

Here's my print out.

A bit of interpretation:

Fast Idle test

Engine RPM             Allowable range 2500 - 3000         Actual       2823

CO                         Allowable           0.2%                           Actual       0.0%

Hydrocarbons     Allowable        200ppm                        Actual        5ppm

Lambda               Allowable         0.97 - 1.03                   Actual          1.00

Natural Idle test

Engine RPM             Allowable range 450-1500             Actual      736

CO                       Allowable        0.3%                                 Actual     0.0%

My car is 2006, 63000 miles. Still with original spark plugs.

 

[james250]

Thanks @johnatg

My Fast Idle Readings on recent MOT is:
CO: 0.006%
Hydrocarbons: 154
Lambda: 0.997

On Natural Idle Readings were:
CO: 0.009%

The most obvious huge difference between mine and yours is the Hydrocarbons. This indicates an issue right? my Lambda reading is a slight lower than yours, what is the Lambda reading?

[johnatg]

Your readings are within MoT limits but they do indicate an issue - and it could be any of lots of different things.

Lambda represents the ratio of the amount of oxygen actually present in a combustion chamber compared to the amount that should have been present in order to obtain "perfect" combustion. Thus, when a mixture contains exactly the amount of oxygen required to burn the amount of fuel present, the ratio will be one to one (Ll) and lambda will equal 1.00. If the mixture contains too much oxygen for the amount of fuel (a lean mixture), lambda will be greater than 1.00. If a mixture contains too little oxygen for the amount of fuel (a rich mixture), lambda will be less than 1.00.

The above is cribbed from an excellent article (lecture notes?} here: http://www.austincc.edu/wkibbe/lambda

so rather than write my own essay I refer you to that!

[ColinBarber]

If the sensors you changed are genuine Denso A/F ratio sensors then you need to look elsewhere.

The following are the workshop manual troubleshooting areas to investigate (in order of likelihood):

 

[james250]

19 hours ago, johnatg said:

Your readings are within MoT limits but they do indicate an issue - and it could be any of lots of different things.

@johnatg I think all the other readings are almost identical to yours except the hyrdrocarbon reading which seems to be much higher on mine. The Lambda reading if rounded to 2 decimal points is 0.99%. Does a high hydrocarbon reading indicate anything in particular?

@ColinBarber  I purchased two brand new sensors from the USA which appear to be Japanese version of the Denso sensors. But there is a chance that these could be replicas. If they are replicas then they must be really good replicas. It's etched with Denso part number and denso name on it. At first I was thinking maybe one of the new sensors but the problem is now the codes are randomly changing from bank 1 to bank 2. One day it's bank 1 and another day it's bank 2. I still have my originals which are disgustingly covered in soot. Wondering if there is a way to clean them up and test them with a multimeter and then maybe put those back in and see what happens? The seller I bought the sensors from has sold many of them and has very good feedback. Another thing i've noticed is that first few days my mpg was really bad. It became worse than ever. But recently when the code changed to bank 2 the mpg has improved. Not sure if that indicates anything?

[johnatg]

Your calculation of the difference in our lambda readings is not valid - there is a world of difference between 1.000 and 0.997. 1.000 indicates exactly stoichiometric combustion - 0.997 is right on the limits of spec but indicates a rich-ish mixture - ie too much fuel for the oxygen in the cylinders. (And your high-ish HC reading concurs). I know your error codes are showing too lean, but your lambda is showing too rich (if it's correct) That can be caused by a variety of things - eg blocked air filter, slight misfire - plug or coil, faulty temperature sensor (the one feeding the ecu is not the same as the one which drives your temperature gauge), etc.

I think you need some tuning diagnosis rather than relying on error codes, because they are all over the place. Maybe try a mobile tuner with an oscilloscope - that can also show the actual output from the O2 sensors.

Are you using Techstream to retrieve the codes, or a generic code reader?

The emissions are not wildly out (and indeed are within MoT specs), so the problem is likely to be minor and intermittent at the moment. I can't explain the error codes reading as they apparently do, but they can sometimes be quite misleading.

[normski2]

Sorry to read of your problems. For me it was just plug and play and off I went.

Couple of things spring to mind...but they are just thoughts...I make no claims of expertise.

• Are you sure you got all those connectors to the ecu (under the Battery tray) all securely refitted? Some of them are right little toads to get at ...no bent pins anywhere on them?
• Don't think you would have ... but did you disconnect the Mass air flow meter or the piping to it and the airfilter box? If you did ... is that big circlip tightened up again? Is the plug attached securely to the MAF meter sensor. 
• May be worth giving the MAF a clean if you have the correct solvent spay available.

I suspect your O2 sensors are OK so try and double check all your re-connections if you can.

Best of luck with it all.