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P2195 on a 2005 focus ST 2.3l

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#21 ·
An EGR leak should post other codes.......have you checked the most common lean leak on those, the PCV hose buried under/behind the intake?
 
Discussion starter · #22 ·
amc49 said:
An EGR leak should post other codes.......have you checked the most common lean leak on those, the PCV hose buried under/behind the intake?
Click to expand...
yes
And I have replaced it twice for good measure took the intake manifold off yesterday couldnt locate any cracked or leaks changed the gaskets again to be safe as well no dice ... I think ill try to smoke test it for leaks if I cant find anything there I guess fuel delivery is next
 
Discussion starter · #23 ·
moe0813 said:
amc49 said:
An EGR leak should post other codes.......have you checked the most common lean leak on those, the PCV hose buried under/behind the intake?
Click to expand...
yes
And I have replaced it twice for good measure took the intake manifold off yesterday couldnt locate any cracked or leaks changed the gaskets again to be safe as well no dice ... I think ill try to smoke test it for leaks if I cant find anything there I guess fuel delivery is next
Click to expand...
Still no luck
Sprayed carb cleaner around the intake around the hoses and I get no change in rpm, would a failing fuel pump theow this code (although there are no signs of a faiking fuel pump other than the random surging, but when I give it more gas it smoothens out )
 
Discussion starter · #24 ·
Okay I got a scanner that can read live data ... Heres what baffles me ig I clear the code car goes into closed loop and reads voltage from the sensor once the ecu senses that lean condition it goes to open loop and the sensor flatlines at 0.000... I'm baffled ive done a smoke test nothing maf is reading fine I can't see any vacuum leaks once the car throws the code it runs fine before the code is thrown it runs awful... Can anyone make sense of this situation before it goes to the mechanic( hate having to bring it there as I can usually fix mostly every thing myself)
Thank you
 
#25 ·
moe0813 said:
Okay I got a scanner that can read live data ... Heres what baffles me ig I clear the code car goes into closed loop and reads voltage from the sensor once the ecu senses that lean condition it goes to open loop and the sensor flatlines at 0.000... I'm baffled ive done a smoke test nothing maf is reading fine I can't see any vacuum leaks once the car throws the code it runs fine before the code is thrown it runs awful... Can anyone make sense of this situation before it goes to the mechanic( hate having to bring it there as I can usually fix mostly every thing myself)
Thank you
Click to expand...
I'm not the best at this subject, but let me try...

First, a quick review of a healthy engine: Open and closed-loop is a mode of the PCM. The engine does not switch from/to open or closed-loop; the PCM "decides" when to run the engine in open or closed-loop mode. The PCM decides when & which mode to operate the engine based on multiple engine sensors.

Open-loop: the engine is running (air-fuel ratio) based on a preset table of data stored within PCM memory. Most or all cars start-up in open-loop mode.

Closed-loop: the engine is running (air-fuel ratio) based on LIVE data of multiple engine sensors.

My PCM starts the engine in open-loop, and about 10 seconds later it enters into closed-loop and stays in closed loop during my drives & normal trips. IIRC the PCM will only switch back into open-loop when you punch the gas pedal (WOT).

Your story (above) has an expected behavior AND another somewhat odd or unexpected behavior.

The expected behavior: Because of your engine problem, your engine is normally running in open-loop (not good). With the engine running, you clear the code and this forces the PCM into closed-loop. The PCM detects abnormal readings from LIVE data (mostly the #1 O2 sensor?) and the PCM screams NO!! The PCM decides that LIVE data is incorrect OR it assumes the data is correct and is harmful to the engine; so the PCM switches to a safer/better set of air-fuel-ratio, which is open-loop ((that preset table of data stored within PCM memory)). This PCM behavior seems normal and expected BECAUSE of your engine problem (vac leak?) and/or because of a defective #1 O2 sensor or wiring. Let me clarify something; the PCM does not know if sensor data is correct or bad data, a good or bad sensor, or if wiring is messed up. The PCM does not think. The PCM only responds based on what is programmed into the PCM firmware. However, there are unique codes where the code translates to "the PCM suspects a wiring problem", a wiring problem might exist.

The odd behavior: Once your PCM switches from closed-loop to open-loop, the data stream from the PCM "flat-lines" the #1 O2 sensor, as shown in your scan tool. This seems like odd behavior to me, HOWEVER it might be normal. You will need someone with that situation experience, and might need experience in your exact situation to verify if that is normal or not.

Gd Luck
 
#26 ·
If the sensor went to 0.0 because it's bad or grounded/disconnected then it would force open loop. it's usually not the sensor but maybe it is? Alternative explanation is that some big lean condition is happening as a kind of step change. For example the EGR is opening. Can you tell what kind of conditions are correlated with the change from closed to open loop? Does it always happen so many minutes after starting and idling, or after a certain kind of driving?

Do a visual inspection of the o2 sensor wiring and connectors. You could look at the sensor and ECU input by back probing the sensor signal line while it's operating, watching the voltage with a multimeter, and seeing if the voltage matches what you see on the scanner. If it lines up then pull off the sensor connector and see if the sensor reading still looks good on the multimeter (while the engine is running, ideally while it's in the initial closed loop phase). If the sensor's output now looks normal this would indicate a good sensor but that the sensor connector is being grounded or pulled to 0 by the ECU.

In a good running system you can push the o2 sensor reading around by causing a lean condition by creating a large vacuum leak, or by causing a rich condition by squirting brake cleaner into the intake. You can do these things as an experiment to check out sensor operation.

Here is a youtube video on an o2 sensor diagnosis:

Again, it's usually not the sensor, but maybe it is this time (or the wiring). You're at about the point where you could throw a new o2 sensor at it, if you didn't want to diagnose further (have you done this?)
 
Discussion starter · #27 ·
zz0rr said:
If the sensor went to 0.0 because it's bad or grounded/disconnected then it would force open loop. it's usually not the sensor but maybe it is? Alternative explanation is that some big lean condition is happening as a kind of step change. For example the EGR is opening. Can you tell what kind of conditions are correlated with the change from closed to open loop? Does it always happen so many minutes after starting and idling, or after a certain kind of driving?

Do a visual inspection of the o2 sensor wiring and connectors. You could look at the sensor and ECU input by back probing the sensor signal line while it's operating, watching the voltage with a multimeter, and seeing if the voltage matches what you see on the scanner. If it lines up then pull off the sensor connector and see if the sensor reading still looks good on the multimeter (while the engine is running, ideally while it's in the initial closed loop phase). If the sensor's output now looks normal this would indicate a good sensor but that the sensor connector is being grounded or pulled to 0 by the ECU.

In a good running system you can push the o2 sensor reading around by causing a lean condition by creating a large vacuum leak, or by causing a rich condition by squirting brake cleaner into the intake. You can do these things as an experiment to check out sensor operation.

Here is a youtube video on an o2 sensor diagnosis:

Again, it's usually not the sensor, but maybe it is this time (or the wiring). You're at about the point where you could throw a new o2 sensor at it, if you didn't want to diagnose further (have you done this?)
Click to expand...
Ive put in 2 new NTK sensors which are oem I was told ... Same thing, wiring looks fine ... However I haven't traced it back to the ecu yet ... I will try the back probing method see if I can come up with anything last time I did this I was getting a reading of around .865 volts but the scanner live was reading at 0.000 so that's where I'm confused is the signal wire bad ? Or is it a bad ground ? I would assume a bad ground would send voltage extremely high but im not too sure wiring/electric was never my thing...
 
#28 ·
If you read voltage on the signal wire while it was plugged into the ecu and the ecu read 0.0 V (I think this is what you're saying) then you've really narrowed your problem down, that's huge. A disconnected wire, bad connector, or bad ground could all cause that. Try finding the ecu pin that reads this sensor and applying a voltage to the pin while the sensor is disconnected. Then you'll know if the ecu input is fried or not. It is probably fine because you do read voltage at the beginning. Clean all your grounds. The main ecu ground is behind the carpet on the passenger side, right inside the car below the front of the door, on the door sill. It usually doesn't go bad but it's worth looking at. You can also remove and clean the ecu connector.
 
Discussion starter · #29 ·
So now I am convinced its not a wiring issue but more of a super lean condition ... Started the car up after work ans o2 readings were 100% normal for 5 miles I was getting voltage pulled onto the highway started to accelerate and boom no more voltage being read from b1s1 this is confusing.
 
Discussion starter · #30 ·
Here's another fact ... Sometimes not always when coming to a stop cars rpms will drop low like its ready to stall then bounce back up to 750 and hang there ... I've had my friends shop smoke test it 3 times carb cleaner vacuum leak test and propane vac test it its not coming up with a vacuum leak so for it to be lean either too much air or not enough fuel ... Could my fuel pump be on its way out ? A sticky injector? Put a screw driver to all 4 all 4 seem to "click" evenly
 
#31 ·
if you suspect the fuel pump you can watch the fuel pressure sensor on obd data while driving, it targets 40psi and should be super stable, within a few psi, on a good running car

injectors can be tested for flow with an injector pulse tester while watching the fuel pressure drop and noting how much the pressure drops on each injector, starting from full 40 psi each time (from a key on engine off fuel pump event). there's no schrader valve or other fitting on the focus fuel rail which is normally where you'd watch the pressure drop so you have to use the obd sensor

see this video on injector pulse testing. it requires an inexpensive chinese pulse box

 
Discussion starter · #33 ·
Doing more research the code is saying the ECU is trying to lean out a rich condition ... That changes the ball game what causes a rich condition ? Too much fuel? Not enough air flow ? Vac leaks ?
 
Discussion starter · #34 ·
zz0rr said:
do you think your open loop/ lean condition is correlated with the engine reaching operating temperature? Does it always happen after a few minutes of running?
Click to expand...
No its completely random and thats what I dont get sometimes it stumbles the minute it turns on other times it doesnt show any symptoms at all the whole 25 min drive to work ... I'm going to test the injectors the live data is roughly 40 psi all the time
 
Discussion starter · #35 ·
zz0rr said:
do you think your open loop/ lean condition is correlated with the engine reaching operating temperature? Does it always happen after a few minutes of running?
Click to expand...
I just left work and sure enough as soon as the engine operating temp it went into open loop what does this mean...? Thanks for your help I really appreciate it
 
#36 ·
p2195 means o2 sensor stuck at 0.0V and it's indicative of a persistent super lean condition or a bad sensor (or connection, or ground, or ECU input)

The most interesting thing is still differentiating between an actual lean condition and a bad reading. You want to duplicate the fault, then while the car is running you should measure the o2 sensor's voltage directly, and so on: investigating grounds, ECU input and wiring if the voltage is good but the ECU sees 0.0 volts, which means this is a sensor problem and not a lean condition.

If you measure an actual 0.0V while the fault is occurring then you know it's a true lean condition, and the ECU is seeing the true sensor reading, and the sensor/wiring/ECU are probably good, a you need to look at air/fuel type causes.

I don't think your diagnosis can proceed until you do this test. Apologies if you've already done it, a few posts ago you did say you back probed the o2 sensor but I couldn't tell the conditions and test setup.
 
Discussion starter · #37 ·
zz0rr said:
p2195 means o2 sensor stuck at 0.0V and it's indicative of a persistent super lean condition or a bad sensor (or connection, or ground, or ECU input)

The most interesting thing is still differentiating between an actual lean condition and a bad reading. You want to duplicate the fault, then while the car is running you should measure the o2 sensor's voltage directly, and so on: investigating grounds, ECU input and wiring if the voltage is good but the ECU sees 0.0 volts, which means this is a sensor problem and not a lean condition.

If you measure an actual 0.0V while the fault is occurring then you know it's a true lean condition, and the ECU is seeing the true sensor reading, and the sensor/wiring/ECU are probably good, a you need to look at air/fuel type causes.

I don't think your diagnosis can proceed until you do this test. Apologies if you've already done it, a few posts ago you did say you back probed the o2 sensor but I couldn't tell the conditions and test setup.
Click to expand...
I did back probe the o2 it read voltage that was consistent with the throttle if I opened throttle voltage dropped let it idle it was .8-.3 fluctuating howrver scanner did not pick up on this ... This is my 3rd sensor and its from ford motorcraft so the o2 reads but the computer doesn't after a while. What makes absolutely no sense after my 12 hour shift car is cold I start it up computer gets reading from o2 drive maybe 3 miles o2 flatlines again at 0... Leads me to believe it isn't a sensor or communication problem maybe a temp sensor issue ? (Guage claims fully warmed up when this occurs)
 
Discussion starter · #38 ·
Ill attach a video of it from a cold start after sitting over night o2 sensor was reading for 10 mins, hit 90degrees Celsius and went into open loop and o2 stopped reading ... I'll attach the Google drive link shortly
 
Discussion starter · #39 ·
https://drive.google.com/open?id=17qHgil3BOzeHCBOuF2fT5cZPT_3Ld2CX
this is the video of me back probing the o2 sensor apparently had the positive connected to negative wire because when switched it read positive all that matters is that the sensor is giving voltage (this is back probed to the 2 wires that are NOT the heater circuit wires)
https://drive.google.com/open?id=1CAFuHudU_6CrVk23Q0Gh1mJlpWVzg6ry
heres the live data stream to show that the ECU does pick up on the o2 sensor voltage... so that rules out the sensor and or wiring to the ecu correct?
thanks ! hopefully this can get resolved soon !!
 
#40 ·
moe0813 said:
https://drive.google.com/open?id=17qHgil3BOzeHCBOuF2fT5cZPT_3Ld2CX
this is the video of me back probing the o2 sensor apparently had the positive connected to negative wire because when switched it read positive all that matters is that the sensor is giving voltage (this is back probed to the 2 wires that are NOT the heater circuit wires)
https://drive.google.com/open?id=1CAFuHudU_6CrVk23Q0Gh1mJlpWVzg6ry
heres the live data stream to show that the ECU does pick up on the o2 sensor voltage... so that rules out the sensor and or wiring to the ecu correct?
thanks ! hopefully this can get resolved soon !!
Click to expand...
that first video looks like the sensor voltage is correct but the ECU isn't seeing it (flatlined at 0.0). So you have some intermittent fault with wiring/connectors, a ground, or an ECU internal intermittent fault. The second video shows OK oscillating voltage on the o2 sensor, not good because it's going from 0-.5V instead of a better .3-.8 or so, but decent. I think we can ignore this because you nailed the intermittent fault in the first video.

Wiring/connectors: You can set up a continuity test from the sensor's connector to the same wire in the ECU connector (in the passenger footwell). Say, with a test light and voltage on one end. Then massage the wires and see if you can get the test light to go out. It's an intermittent fault so you will need to work to replicate it, don't just move on once you get a good test light reading. Also clean the connectors at the ECU and at the sensor.

Grounds: Inspect and clean your grounds. You do this by removing the grounding screw, scrubbing underneath it with something abrasive to get shiny metal especially on the wire crimp donut, and reinstalling tightly. There are 2-3 grounds near the ECU, under the carpet, and 4 or 5 in the engine bay. I don't know which is used for the o2 sensor input, maybe a ford wiring diagram would show this. You can get a ripped factory wiring diagram on ebay for $20 or so.

ECU input: If you are satisfied that the wires, connectors and grounds are not a problem then you should try to replicate the problem (reading 0.0V on OBD data) then apply a voltage to the ECU input pin and see if the ECU reads what you apply. Normally these pins are protected from battery voltage so you can apply 12V and you'll see 5V (or some other max reading). But maybe that can damage something? I don't know. Ideally you'd apply 5V or 3V or whatever so it wouldn't be out of range. This test will look at whether the ECU's input is bad (internal to the ECU).
 
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