FF25C8 error code

R1pilot · 11-10-2022, 06:35 PM

Hi,

I got a check engine light right after I refilled the DEF tank on my wife's 2014 328xD.

Both the Schwaben tool and INPA (Mikes easy BMW Tools dl) did not recognize this car even though they work on my e46 M3 and e92 M3. After going through this forum and reading a few threads I downloaded BimmerLink and was able to read the code. It came back, as the title states, as:

FF25C8

Does anyone have any idea what the code is? The app basically calls out the code but states that no description is available.

Any help is appreciated. Thanks!

Enabled · 11-10-2022, 07:06 PM

This is a little known bimmerlink glitch/issue in their program. It added FF in front of the actual code.

Luckily there was only one 25C8xx code (sometimes there are multiple).

25C800 Exhaust backpressure sensor: sensor drifting out of tolerance

It's worth cleaning the exhaust backpressure sensor or the little tube going to the sensor before replacing it. If cleaning the exhaust backpressure sensor or the tube didn't help, then replace the sensor. It is the one mounted in the exhaust manifold.

For what it's worth, INPA works fine with these cars. Get a good ENET cable and use that. I assume you're using a kdcan, which isn't the optimal one for these.

It the Schwaben tool doesn't work either, then the pins at your OBD port are pushed in, specifically pins 6 and/or 14 (for CANBUS). Dismount the OBD port and inspect the pins and push them back down. This is a common issue with ports that have been forced.

ENET cable uses different pins, so that's why Bimmerlink works. However, as you can see, Bimmerlink has some glitches.

R1pilot · 11-10-2022, 07:13 PM

As usual Enabled to the rescue! THANKS!!

My copy of INPA is somewhat old. I could connect to the car and actually select N47 but it would give me an error that I attributed to the version not being correct. I will do some research on the cable and also check the pins on the port. The more things I can connect the better.

Now off to the interwebs to find where that sensor is in the car! From what I saw already its not that expensive of a fix if it needs a new one.

One last quick question ... do you think this was related to me refilling the DEF tank or just a coincidence?

Thanks again.

Enabled · 11-10-2022, 07:15 PM

Coincidence!

The sensor is at the end of a small metal tube coming off the exhaust manifold.

I've had that error a couple of times on mine, only when it was cold outside.

So cleaning it and the tube with electrical contact cleaner, or some of those soft pipe cleaners may completely resolve it.

R1pilot · 11-10-2022, 07:29 PM

Got it!

I will try and clean it tomorrow and go from there.

If anyone else has this problem, given Enabled's description and what I found online, I am pretty sure this is the part in the picture below. Its extremely easy to access.

PN should be 13628507634 (edited PN to reflect correct sensor!) according to realoem

(Pic updated!!)

Enabled · 11-10-2022, 07:40 PM

Nope, that's the differential pressure sensor.

What you're looking for is in your picture, just a few inches forward

R1pilot · 11-10-2022, 08:21 PM

Doh, I think I got it now. I updated both the PN and picture to not confuse anyone.

R1pilot · 11-12-2022, 06:13 PM

OK people following along ... it kind of turned into a mess as usual for me, but I cleared the code and we'll see if it returns. I just got done swapping the clutch on my e92 M3 last week and it was a walk in the park compared to this lol.

I first failed to unplug the sensor, I could not figure out for the life of me how to do it. I moved the lock up and down and pressed and fought for 30 minutes with no luck. I then decided to disconnect the hose from the sensor ... the stupid clamp is made in a way that the wrench or screwdriver will only tighten it, like a safety screw to not be removed. I grabbed it with some pliers and was able to undo it but it was impossible to get the short hose off of the sensor. Here is where the fun starts.

I decided to attack the banjo bolt that secures the hard line to the exhaust manifold with a 17mm wrench. There is also a tiny etorx E8 holding the line and the manifold heat shield. Even though I am in Florida and rust is nonexistent the heat had done a number on that bolt and I could only loosen it 1/8 of a turn at most. I know better and before I stripped it I brought out the PB Blaster and a torch and started slowly dowsing it while applying heat. I spent 30 minutes while slowing turning the bolt both ways. Finally got it out. Great ... I guess.

The last two threads where stripped and I went into panic mode contemplating both the price of a new manifold and the difficulty of swapping it. Decided to concentrate on cleaning what I had, which was filthy.

I then decided to reattach and see if the threads would catch or not. It went in, the last 1/4 was difficult but I tightened it slowly and finally was able to get it all the way in. Unfortunately I reused the copper crush washers as I did not have extra ones, but it seems like its all sealed up properly.

I own BMWs of all years and this one is the one that always kicks my but, starting with the stupid transfer case ... now to figure out what the hell is going on with the screen and how to fix this crap.

Thanks gents, especially Enabled!!

Some pics because everyone loves pics:

R1pilot · 11-13-2022, 08:40 PM

Went on a 120 mile round trip, 95% highway. I stopped for lunch at mile 55 and when I got in the car after lunch the check engine light popped up. Excellent.

Got home and had the same code, plus another one. The codes where:

25C800 - We already went over this, looks like this is a "permanent" code and triggers the check engine light. "Exhaust back pressure sensor: sensor drift outside of tolerance".

258700 - Will not trigger a check engine light. "Exhaust back pressure sensor: signal too low".

Funny thing is that, based on the mileage the errors were triggered at, the software things my car has about 1k miles than indicated

... bought it from a BMW dealer with 18k miles so I am sure my mileage is correct.

Anyways, I ordered the sensor ... Will update the thread ones it comes in. Hopefully I can figure out how to unclip it from the harness this time.

Enabled · 11-14-2022, 02:58 PM

The gray part pulls up as you did, then you squeeze that gray tab you pulled inward, which should raise the locking lever tab.

Often it helps to advance the plug forward a bit, and then the locking tab will release better.

R1pilot · 11-19-2022, 05:31 PM

Swapped the sensor this morning, drove the car about 25 miles and no light.

I will update back next weekend when I drive it whether the light stays off or not. No way my wife will notice it.

That plug was a total bitch to remove, as Enabled said all that was needed was to pull back the grey lock and put pressure on the tab like you want to make it into a diamond.

R1pilot · 11-22-2022, 11:53 AM

180 miles in the pesky light decided to light up again. Same code

Enabled · 11-22-2022, 12:25 PM

Quote:

Originally Posted by R1pilot

180 miles in the pesky light decided to light up again. Same code

Can you use some pipe cleaners and clean that tube really really well? If you haven't already?

R1pilot · 11-22-2022, 02:22 PM

I will give it a shot. I have some pipe brushes that should bend enough to get all the way through.

Do you remove it from the manifold when cleaning? I am somewhat scared of removing that banjo bolt.

Enabled · 11-28-2022, 06:08 PM

That banjo bolt will require a lot of PB Blaster and/or heat. I didn't remove it at all.... I got lucky to get the same codes lately.

Seen in order:

I took a picture of what the tube looked like. It's pretty obvious.

Then I made my Super Special BMW T-Handle Curette Tool (SSBTHCT for short), and did some cleaning/curettage. I used a compressor to blow the remaining bits out.

The end result.

It's worth noting that the tube is 8 years old and the rubber layer inside looks like it is deteriorating. I'll be replacing it next time.

Enabled · 01-25-2023, 11:27 AM

I did more investigating into this code: 25C800 Exhaust backpressure sensor: sensor drifting out of tolerance, specifically the software routine around error debounce (error popping up). This has to do with the steps that the ECU takes to determine there's an issue and when it will throw a DTC and/or pop up the CEL.

The error debounce happens if the absolute value of the "raw value of the corrected absolute backpressure" is greater than 30 hPa for USA cars. Many Euro cars, probably EU5, have the tolerance set at 60hPa (but they also measure differently, for example using comparison to the barometric pressure sensor. USA does not).

For the USA cars, the "raw value of the corrected absolute backpressure" is a value determined by measurements between the backpressure sensor and the differential pressure sensor. So the sensors and especially the pressure pipes/tubes have to be undamaged and unblocked.

For my car, when I had the error, my "raw value of the corrected absolute backpressure" was -33.53 hPa read from the code's environmental conditions. This means that there was a -33.53 hectoPascal difference between the readings. So in the USA calibration (30 hPa tolerance limit) my 33.53 hPa difference was past the allowed limit, therefore I got a DTC and CEL.

This data suggests that the tube is potentially blocked or leaking out. I had a spare sensor handy and it didn't change a thing. Often it's not the sensor's fault.

Hopefully some can use this information to determine what (simple) repairs would be needed.

mketch · 11-26-2023, 03:24 PM

Adding my experience to solving the 25C800 Exhaust backpressure sensor: sensor drifting out of tolerance - Fault Code...

My journey:

1) Pull Backpressure Sensor and Metal / Rubber Tubing - As others have said, removing the banjo bolt was not fun and time consuming - lots incremental loosening and tightening with plenty of penetrating oil. It also required the threads be chased, as well as a new banjo bolt to be purchased.

2) Thoroughly Clean Metal / Rubber Tubing and reset code. Code returned.

3) Replace Metal / Rubber Tubing and Back Pressure Sensor and reset code and adaptations. Code returned.

4) Replace Differential Pressure Sensor and reset code and adaptations. 250 miles thus far and a mix of short and longer trips - no codes. Will modify this post if it comes back.

Even though the code was for the Back Pressure Sensor, it seems (per Enabled above) the Back Pressure Sensor uses the Differential Pressure Sensor as a basis for the tolerance measurement.

Note: My original Differential Pressure Sensor was showing negative values at idle. This corrected after replacement.

11-10-2022, 06:35 PM	#1
R1pilot New Member 7 Rep 27 Posts Drives: BMW 328xd Join Date: May 2020 Location: Florida iTrader: (0)	FF25C8 error code Hi, I got a check engine light right after I refilled the DEF tank on my wife's 2014 328xD. Both the Schwaben tool and INPA (Mikes easy BMW Tools dl) did not recognize this car even though they work on my e46 M3 and e92 M3. After going through this forum and reading a few threads I downloaded BimmerLink and was able to read the code. It came back, as the title states, as: FF25C8 Does anyone have any idea what the code is? The app basically calls out the code but states that no description is available. Any help is appreciated. Thanks! __________________ '87 325is / '97 M3 / '04 M3 / '14 328xd
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11-10-2022, 07:06 PM	#2
Enabled Lieutenant Colonel 1429 Rep 1,821 Posts Drives: 328xd Wagon, M2 Competition Join Date: Jun 2018 Location: Houston iTrader: (0)	This is a little known bimmerlink glitch/issue in their program. It added FF in front of the actual code. Luckily there was only one 25C8xx code (sometimes there are multiple). 25C800 Exhaust backpressure sensor: sensor drifting out of tolerance It's worth cleaning the exhaust backpressure sensor or the little tube going to the sensor before replacing it. If cleaning the exhaust backpressure sensor or the tube didn't help, then replace the sensor. It is the one mounted in the exhaust manifold. For what it's worth, INPA works fine with these cars. Get a good ENET cable and use that. I assume you're using a kdcan, which isn't the optimal one for these. It the Schwaben tool doesn't work either, then the pins at your OBD port are pushed in, specifically pins 6 and/or 14 (for CANBUS). Dismount the OBD port and inspect the pins and push them back down. This is a common issue with ports that have been forced. ENET cable uses different pins, so that's why Bimmerlink works. However, as you can see, Bimmerlink has some glitches. __________________ -2014 328d Wagon, 8HP. Self-tuned, 270hp/430ft-lbs. -2019 M2 Competition MT, Alpine White. Self-tuned 560hp -2016 Mini Cooper S, MT. Many plans. Others: -E36 328is. 2000 Z3 Roady. 2003 VW Jetta TDI Manual. Estoril Z3M Coupe.
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11-10-2022, 07:13 PM	#3
R1pilot New Member 7 Rep 27 Posts Drives: BMW 328xd Join Date: May 2020 Location: Florida iTrader: (0)	As usual Enabled to the rescue! THANKS!! My copy of INPA is somewhat old. I could connect to the car and actually select N47 but it would give me an error that I attributed to the version not being correct. I will do some research on the cable and also check the pins on the port. The more things I can connect the better. Now off to the interwebs to find where that sensor is in the car! From what I saw already its not that expensive of a fix if it needs a new one. One last quick question ... do you think this was related to me refilling the DEF tank or just a coincidence? Thanks again. __________________ '87 325is / '97 M3 / '04 M3 / '14 328xd
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11-10-2022, 07:15 PM	#4
Enabled Lieutenant Colonel 1429 Rep 1,821 Posts Drives: 328xd Wagon, M2 Competition Join Date: Jun 2018 Location: Houston iTrader: (0)	Coincidence! The sensor is at the end of a small metal tube coming off the exhaust manifold. I've had that error a couple of times on mine, only when it was cold outside. So cleaning it and the tube with electrical contact cleaner, or some of those soft pipe cleaners may completely resolve it. __________________ -2014 328d Wagon, 8HP. Self-tuned, 270hp/430ft-lbs. -2019 M2 Competition MT, Alpine White. Self-tuned 560hp -2016 Mini Cooper S, MT. Many plans. Others: -E36 328is. 2000 Z3 Roady. 2003 VW Jetta TDI Manual. Estoril Z3M Coupe.
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11-10-2022, 07:29 PM	#5
R1pilot New Member 7 Rep 27 Posts Drives: BMW 328xd Join Date: May 2020 Location: Florida iTrader: (0)	Got it! I will try and clean it tomorrow and go from there. If anyone else has this problem, given Enabled's description and what I found online, I am pretty sure this is the part in the picture below. Its extremely easy to access. PN should be 13628507634 (edited PN to reflect correct sensor!) according to realoem (Pic updated!!) __________________ '87 325is / '97 M3 / '04 M3 / '14 328xd Last edited by R1pilot; 11-10-2022 at 08:20 PM.. Reason: Edited to reflect correct sensor as pointed by Enabled
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11-10-2022, 07:40 PM	#6
Enabled Lieutenant Colonel 1429 Rep 1,821 Posts Drives: 328xd Wagon, M2 Competition Join Date: Jun 2018 Location: Houston iTrader: (0)	Nope, that's the differential pressure sensor. What you're looking for is in your picture, just a few inches forward
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11-10-2022, 08:21 PM	#7
R1pilot New Member 7 Rep 27 Posts Drives: BMW 328xd Join Date: May 2020 Location: Florida iTrader: (0)	Doh, I think I got it now. I updated both the PN and picture to not confuse anyone. __________________ '87 325is / '97 M3 / '04 M3 / '14 328xd
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11-12-2022, 06:13 PM	#8
R1pilot New Member 7 Rep 27 Posts Drives: BMW 328xd Join Date: May 2020 Location: Florida iTrader: (0)	OK people following along ... it kind of turned into a mess as usual for me, but I cleared the code and we'll see if it returns. I just got done swapping the clutch on my e92 M3 last week and it was a walk in the park compared to this lol. I first failed to unplug the sensor, I could not figure out for the life of me how to do it. I moved the lock up and down and pressed and fought for 30 minutes with no luck. I then decided to disconnect the hose from the sensor ... the stupid clamp is made in a way that the wrench or screwdriver will only tighten it, like a safety screw to not be removed. I grabbed it with some pliers and was able to undo it but it was impossible to get the short hose off of the sensor. Here is where the fun starts. I decided to attack the banjo bolt that secures the hard line to the exhaust manifold with a 17mm wrench. There is also a tiny etorx E8 holding the line and the manifold heat shield. Even though I am in Florida and rust is nonexistent the heat had done a number on that bolt and I could only loosen it 1/8 of a turn at most. I know better and before I stripped it I brought out the PB Blaster and a torch and started slowly dowsing it while applying heat. I spent 30 minutes while slowing turning the bolt both ways. Finally got it out. Great ... I guess. The last two threads where stripped and I went into panic mode contemplating both the price of a new manifold and the difficulty of swapping it. Decided to concentrate on cleaning what I had, which was filthy. I then decided to reattach and see if the threads would catch or not. It went in, the last 1/4 was difficult but I tightened it slowly and finally was able to get it all the way in. Unfortunately I reused the copper crush washers as I did not have extra ones, but it seems like its all sealed up properly. I own BMWs of all years and this one is the one that always kicks my but, starting with the stupid transfer case ... now to figure out what the hell is going on with the screen and how to fix this crap. Thanks gents, especially Enabled!! Some pics because everyone loves pics: __________________ '87 325is / '97 M3 / '04 M3 / '14 328xd
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11-13-2022, 08:40 PM	#9
R1pilot New Member 7 Rep 27 Posts Drives: BMW 328xd Join Date: May 2020 Location: Florida iTrader: (0)	Went on a 120 mile round trip, 95% highway. I stopped for lunch at mile 55 and when I got in the car after lunch the check engine light popped up. Excellent. Got home and had the same code, plus another one. The codes where: 25C800 - We already went over this, looks like this is a "permanent" code and triggers the check engine light. "Exhaust back pressure sensor: sensor drift outside of tolerance". 258700 - Will not trigger a check engine light. "Exhaust back pressure sensor: signal too low". Funny thing is that, based on the mileage the errors were triggered at, the software things my car has about 1k miles than indicated ... bought it from a BMW dealer with 18k miles so I am sure my mileage is correct. Anyways, I ordered the sensor ... Will update the thread ones it comes in. Hopefully I can figure out how to unclip it from the harness this time. __________________ '87 325is / '97 M3 / '04 M3 / '14 328xd
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11-14-2022, 02:58 PM	#10
Enabled Lieutenant Colonel 1429 Rep 1,821 Posts Drives: 328xd Wagon, M2 Competition Join Date: Jun 2018 Location: Houston iTrader: (0)	The gray part pulls up as you did, then you squeeze that gray tab you pulled inward, which should raise the locking lever tab. Often it helps to advance the plug forward a bit, and then the locking tab will release better.
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11-19-2022, 05:31 PM	#11
R1pilot New Member 7 Rep 27 Posts Drives: BMW 328xd Join Date: May 2020 Location: Florida iTrader: (0)	Swapped the sensor this morning, drove the car about 25 miles and no light. I will update back next weekend when I drive it whether the light stays off or not. No way my wife will notice it. That plug was a total bitch to remove, as Enabled said all that was needed was to pull back the grey lock and put pressure on the tab like you want to make it into a diamond. __________________ '87 325is / '97 M3 / '04 M3 / '14 328xd
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11-22-2022, 11:53 AM	#12
R1pilot New Member 7 Rep 27 Posts Drives: BMW 328xd Join Date: May 2020 Location: Florida iTrader: (0)	180 miles in the pesky light decided to light up again. Same code __________________ '87 325is / '97 M3 / '04 M3 / '14 328xd
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11-22-2022, 02:22 PM	#14
R1pilot New Member 7 Rep 27 Posts Drives: BMW 328xd Join Date: May 2020 Location: Florida iTrader: (0)	I will give it a shot. I have some pipe brushes that should bend enough to get all the way through. Do you remove it from the manifold when cleaning? I am somewhat scared of removing that banjo bolt. __________________ '87 325is / '97 M3 / '04 M3 / '14 328xd
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11-28-2022, 06:08 PM	#15
Enabled Lieutenant Colonel 1429 Rep 1,821 Posts Drives: 328xd Wagon, M2 Competition Join Date: Jun 2018 Location: Houston iTrader: (0)	That banjo bolt will require a lot of PB Blaster and/or heat. I didn't remove it at all.... I got lucky to get the same codes lately. Seen in order: I took a picture of what the tube looked like. It's pretty obvious. Then I made my Super Special BMW T-Handle Curette Tool (SSBTHCT for short), and did some cleaning/curettage. I used a compressor to blow the remaining bits out. The end result. It's worth noting that the tube is 8 years old and the rubber layer inside looks like it is deteriorating. I'll be replacing it next time. Attached Images __________________ -2014 328d Wagon, 8HP. Self-tuned, 270hp/430ft-lbs. -2019 M2 Competition MT, Alpine White. Self-tuned 560hp -2016 Mini Cooper S, MT. Many plans. Others: -E36 328is. 2000 Z3 Roady. 2003 VW Jetta TDI Manual. Estoril Z3M Coupe.
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01-25-2023, 11:27 AM	#16
Enabled Lieutenant Colonel 1429 Rep 1,821 Posts Drives: 328xd Wagon, M2 Competition Join Date: Jun 2018 Location: Houston iTrader: (0)	I did more investigating into this code: 25C800 Exhaust backpressure sensor: sensor drifting out of tolerance, specifically the software routine around error debounce (error popping up). This has to do with the steps that the ECU takes to determine there's an issue and when it will throw a DTC and/or pop up the CEL. The error debounce happens if the absolute value of the "raw value of the corrected absolute backpressure" is greater than 30 hPa for USA cars. Many Euro cars, probably EU5, have the tolerance set at 60hPa (but they also measure differently, for example using comparison to the barometric pressure sensor. USA does not). For the USA cars, the "raw value of the corrected absolute backpressure" is a value determined by measurements between the backpressure sensor and the differential pressure sensor. So the sensors and especially the pressure pipes/tubes have to be undamaged and unblocked. For my car, when I had the error, my "raw value of the corrected absolute backpressure" was -33.53 hPa read from the code's environmental conditions. This means that there was a -33.53 hectoPascal difference between the readings. So in the USA calibration (30 hPa tolerance limit) my 33.53 hPa difference was past the allowed limit, therefore I got a DTC and CEL. This data suggests that the tube is potentially blocked or leaking out. I had a spare sensor handy and it didn't change a thing. Often it's not the sensor's fault. Hopefully some can use this information to determine what (simple) repairs would be needed. __________________ -2014 328d Wagon, 8HP. Self-tuned, 270hp/430ft-lbs. -2019 M2 Competition MT, Alpine White. Self-tuned 560hp -2016 Mini Cooper S, MT. Many plans. Others: -E36 328is. 2000 Z3 Roady. 2003 VW Jetta TDI Manual. Estoril Z3M Coupe. Last edited by Enabled; 01-25-2023 at 11:44 AM..
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11-26-2023, 03:24 PM	#17
mketch Registered 1 Rep 3 Posts Drives: E39, E53, E46, F31, R1200R Join Date: Nov 2019 Location: Portland, OR iTrader: (0)	Adding my experience to solving the 25C800 Exhaust backpressure sensor: sensor drifting out of tolerance - Fault Code... My journey: 1) Pull Backpressure Sensor and Metal / Rubber Tubing - As others have said, removing the banjo bolt was not fun and time consuming - lots incremental loosening and tightening with plenty of penetrating oil. It also required the threads be chased, as well as a new banjo bolt to be purchased. 2) Thoroughly Clean Metal / Rubber Tubing and reset code. Code returned. 3) Replace Metal / Rubber Tubing and Back Pressure Sensor and reset code and adaptations. Code returned. 4) Replace Differential Pressure Sensor and reset code and adaptations. 250 miles thus far and a mix of short and longer trips - no codes. Will modify this post if it comes back. Even though the code was for the Back Pressure Sensor, it seems (per Enabled above) the Back Pressure Sensor uses the Differential Pressure Sensor as a basis for the tolerance measurement. Note: My original Differential Pressure Sensor was showing negative values at idle. This corrected after replacement.
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