Replacing REX fuel temp/pressure sensor

[tangocash]

My check engine light came on recently and the OBD scanner w/ Torque app gave me 3 error codes which, when "translated" online, came to:

P14FA - exhaust gas temp sensor faulty
P0185 - fuel temp sensor B circuit malfunction
P018B - fuel pressure sensor B circuit range/performance

I did attempt to clear these code, just to make sure they weren't phantom errors, but they immediately came back.

Unless someone else can tell me differently, I'm focused on fixing the last 2 codes by replacing the sensor part#16147426661 (https://www.genuinebmwminiparts.com...lA5y8fq-5MaiMQodvgBUiFRHGNQx3vYEaAnjsEALw_wcB) that seems to apply to both temp and pressure. I'm hoping that the faulty sensor at the fuel is having a trickle down affect on the exhaust and fixing the last 2 codes will "fix" the first code by default. Or maybe I'm being naive...

I'm wondering if anyone else has received similar error codes and/or replaced the sensor to fix the issue? Figured I'd ask for experiences before I spend $150+ to replace the part myself? I absolutely hate my local BMW dealer and that gives me even more motivation to do nearly every repair/maintenance myself. I just wish I could easily get a confirmation to make sure this is the part I need to fix the issue.

 

[agzand]

Did you try replacing the fuel pump relay? It is a common fail point for i3.

https://www.amazon.com/gp/product/B00AF532M8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

https://www.ecstuning.com/b-genuine...MIisHv3pHR-QIVGAutBh0dZQTAEAQYASABEgJZmvD_BwE

You can switch it with similar relay for other function to see if that is the culprit.

There are videos on youtube on how to do this.

 

[agzand]

https://www.mybmwi3.com/forum/viewtopic.php?t=4527&start=10

 

[tangocash]

Did you try replacing the fuel pump relay? It is a common fail point for i3.

https://www.amazon.com/gp/product/B00AF532M8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

https://www.ecstuning.com/b-genuine...MIisHv3pHR-QIVGAutBh0dZQTAEAQYASABEgJZmvD_BwE

You can switch it with similar relay for other function to see if that is the culprit.

There are videos on youtube on how to do this.

I haven't tried doing anything yet, but this sounds like a much better (and perhaps cheaper) place to start. Thanks!

And I assume I can ignore that fact that both parts you linked to do not confirm fitment on a 2014 i3?

 

[agzand]

The part number is: 61366915327

I think it is mentioned in this video:
https://www.youtube.com/watch?v=KkF5VvmlZCM

I just think it is unlikely to have several sensors failing at the same time, so it could be the realy.

 

[tangocash]

The part number is: 61366915327

I think it is mentioned in this video:
https://www.youtube.com/watch?v=KkF5VvmlZCM

I just think it is unlikely to have several sensors failing at the same time, so it could be the realy.

Perfect, that's the exact part number I ordered. Just waiting for it to arrive now.

And thanks for the video!

 

[tangocash]

Well I replaced the right-hand side relay behind the glovebox, following the video tutorial. I cleared the codes but the check engine light never disappeared. I've been driving the past few days, hoping the occasional use of the REX would clear it, but nothing has changed.

I've now gone back into the computer and found that these codes are now absent so I guess the relay helped after all:
P0185 - fuel temp sensor B circuit malfunction
P018B - fuel pressure sensor B circuit range/performance

But the following codes are still present or new additions:
P14FA - exhaust gas temp sensor faulty (remaining from before)
P0480 - cooling fan 1 control circuit has a malfunction (new code)

Wasn't the left-hand side relay in the glovebox controlling ventilation/air, or am I remembering that wrong?

My A/C has also been struggling to stay cool (colder at highway speeds and not so cold any other time) and that's a separate post, but could these issues be related?

 

[agzand]

I think the other relay is for the fan, there is also a fuse in the fuse box for the fan.

If the fan works poorly it could be the relay, however I haven't heard many issues with that relay. The fuel pump has more issues because in many cases it is run sporadically.

Also make sure your 12v battery is in good shape and the gas cap works properly.

 

[tangocash]

I think the other relay is for the fan, there is also a fuse in the fuse box for the fan.

If the fan works poorly it could be the relay, however I haven't heard many issues with that relay. The fuel pump has more issues because in many cases it is run sporadically.

Also make sure your 12v battery is in good shape and the gas cap works properly.

I'll have to track down that fan fuse, just in case.

Yourmechanic.com talks about how to diagnose the cooling fan code and mentions these items to consider so I guess I'll look at doing that when the heat subsides a bit. If I'm really lucky, I'll find some obvious, visual evidence of failure.

-Faulty cooling fan 1
-Poor electrical connection in the fan circuit
-Failed fan control relay has failed
-Failed coolant temperature sensor
-Faulty AC pressure switch
-VSS not operating properly

The 12V was replaced 2 years ago so it feels a bit early to start failing, but you never know...

Thanks!

 

[gta3005]

Any updates on these issues? I've got the same two codes, p0480 and p14fa ( thanks for providing what this one is!). I replaced the front fan behind the radiator this weekend because that's what BMW recommended but I still have a historic p0480 fault. Going to try running the rex to get it to go away.

 

[tangocash]

Any updates on these issues? I've got the same two codes, p0480 and p14fa ( thanks for providing what this one is!). I replaced the front fan behind the radiator this weekend because that's what BMW recommended but I still have a historic p0480 fault. Going to try running the rex to get it to go away.

I haven't had a chance to go in and look yet, but my first order of business was going to be a part-by-part inspection along the system to find any visual signs of loose connections and wear that may pinpoint what part is the obvious problem. Replacing the fan sounds like a good start, but now that you've swapped it out, perhaps it's a bad sensor along the path?

Does this mean replacing the fan fixed your P14fa error code, but not the P0480? I've been trying to locate the exhaust temp sensor in the car to see if its a cost effective attempt to fix P14fa.

I need to get my hands on a legit PDF of the service manual so I can better navigate these issues but I haven't yet decided where I'd trust to spend the money.

 

[agzand]

https://attachments.priuschat.com/attachment-files/2016/07/108943_12_W20-Engine.pdf

I think it is item 5 on page 37 (monitoring sensor), but I am not sure.

 

[gta3005]

Interesting PDF, thanks for adding that.

It did not get rid of the P14FA code. I've had that code for a long time and it tends to be intermittent so I haven't been focusing on it. I need to fic the P0480 before the end of month for inspection, so we're gonna find a solution to this!!

I have been meaning to check F72 – 5A – radiator fan relay (https://fuseandrelay.com/bmw/i3.html). I figure if the motor was shot (which it didn't seem to be in horrible condition, just minor resistance compared to the new one) then it could have fried the fuse as the vehicle was trying to run it.

I took a lot of pictures of the fan swap with the intention of creating a DIY. It's not a horrible job, took me probably 6 hours. But, if I had known exactly what I was doing from the beginning, probably would have only taken 2 or 3 hours.

 

[tangocash]

https://attachments.priuschat.com/attachment-files/2016/07/108943_12_W20-Engine.pdf

I think it is item 5 on page 37 (monitoring sensor), but I am not sure.

Great document, thanks! That looks exactly like the part I've been Googling.

 

[tangocash]

Interesting PDF, thanks for adding that.

It did not get rid of the P14FA code. I've had that code for a long time and it tends to be intermittent so I haven't been focusing on it. I need to fic the P0480 before the end of month for inspection, so we're gonna find a solution to this!!

I have been meaning to check F72 – 5A – radiator fan relay (https://fuseandrelay.com/bmw/i3.html). I figure if the motor was shot (which it didn't seem to be in horrible condition, just minor resistance compared to the new one) then it could have fried the fuse as the vehicle was trying to run it.

I took a lot of pictures of the fan swap with the intention of creating a DIY. It's not a horrible job, took me probably 6 hours. But, if I had known exactly what I was doing from the beginning, probably would have only taken 2 or 3 hours.

I too have had the P14FA code come and go for years and, I think you're right, it tends not to trip the engine light. However, the replacement sensor that could potentially clear it is about $40 on eBay so that's an option.

Thanks for the diagram on fuses! I just checked that fuse and (unfortunately) it looks good. Doesn't the 5amp fuse for the "fan relay" mean that there's a separate relay unit somewhere else that may be failing? As I read more about this error code, the fan relay is coming up as another potential cause. Some DIY diagnosis sources also mention other sensors like exhaust temp and O2 as items to consider. What if a bad O2 sensor is throwing off the cooling system's readings and the cooling system is struggling to make it right?

 

[tangocash]

Interesting PDF, thanks for adding that.

It did not get rid of the P14FA code. I've had that code for a long time and it tends to be intermittent so I haven't been focusing on it. I need to fic the P0480 before the end of month for inspection, so we're gonna find a solution to this!!

I have been meaning to check F72 – 5A – radiator fan relay (https://fuseandrelay.com/bmw/i3.html). I figure if the motor was shot (which it didn't seem to be in horrible condition, just minor resistance compared to the new one) then it could have fried the fuse as the vehicle was trying to run it.

I took a lot of pictures of the fan swap with the intention of creating a DIY. It's not a horrible job, took me probably 6 hours. But, if I had known exactly what I was doing from the beginning, probably would have only taken 2 or 3 hours.

I too have had the P14FA code come and go for years and, I think you're right, it tends not to trip the engine light. However, the replacement sensor that could potentially clear it is about $40 on eBay so that's an option.

Thanks for the diagram on fuses! I just checked that fuse and (unfortunately) it looks good. Doesn't the 5amp fuse for the "fan relay" mean that there's a separate relay unit somewhere else that may be failing? As I read more about this error code, the fan relay is coming up as another potential cause. Some DIY diagnosis sources also mention other sensors like exhaust temp and O2 as items to consider. What if a bad O2 sensor is throwing off the cooling system's readings and the cooling system is struggling to make it right?

Something like this?

https://partsouq.com/en/catalog/gen...=$&vid=309009652&cid=685623&uid=2122273826&q=

 

[gta3005]

This is promising. You're correct in that the fuse I mentioned is for a relay, so maybe this relay is bad? Do you know if its a relay that can be purchased at an Auto Zone or if its BMW specialty.

Also, regarding P14FA, where did you find the OBD2 description for this code? I haven't been able to find anything on it. And it confuses me a bit why it would be for exhaust gas temp sensor, as these are typically only for diesel engines. Also can't find anything on the i3 having an exhaust gas temp sensor and an O2 sensor is not the same as EGT sensor.

 

[tangocash]

Also, regarding P14FA, where did you find the OBD2 description for this code? I haven't been able to find anything on it. And it confuses me a bit why it would be for exhaust gas temp sensor, as these are typically only for diesel engines. Also can't find anything on the i3 having an exhaust gas temp sensor and an O2 sensor is not the same as EGT sensor.

Wow, you're right, it's hard to find details about the P14FA code and I don't understand why it's such a "secret". It's been a while since I researched it and it now took me several different Google searches to finally find something useful. I believe this is where I saw it previously, but it's the only mention I could find so I think I just ran with it as the explanation out of lack of options: https://www.engine-codes.com/p14a4_bmw.html

Could there be a glitch where a bad O2 sensor accidentally trips this misleading P14FA "exhaust" code that would normally apply to other BMW models using the same ECU software? Seems odd that you're really the only other i3 owner I've found on the forums talking about this code. Ghost in the machine?

 

[gta3005]

Damn and that's for P14A4 not even P14FA. Worth noting is I'm using Torque also to diagnose, so maybe this is a code that Torque is interpreting and not actually correct?

I'm having a friend with a bit better diagnostic tools take a look at it tomorrow so hopefully he will have a better answer. If he doesn't have a good answer I'm going to be forced to take it to BMW to diagnose. I kind of bugged out on them yesterday trying to get them to just decipher the code. Literally had the vehicle at BMW a couple weeks ago and they mentioned it had the P0480 code, but nothing about the P14FA code. So I'm trying to get them to read the code for free haha.

 

[gta3005]

Full vehicle scan was performed yesterday. Should have more information today. Looking like it's related to the P0480 code. Possibly a lack of communication with computer for cooling system.