Rex Works, tested several times by BMW (maintenance mode and driving), but...

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MrL

Member
Joined
Jul 15, 2023
Messages
6
So, I have been using my BMW i3 to drive deliveries for the past 3 years. Put a quick 115K miles on the car - boom. To me the car drives and sounds still like new, even though I have been side swiped and almost drove off an overpass - LOL. Anyway, while under warranty I kept hearing a clicking / grinding noise coming from the rear of the car. Had it at BMW 2 times and they were unable to identify where it is coming from. So, I kept driving it.

Over Xmas 2022/23 the noise came back. And got stronger. In February 2023 I decided to go back to BMW and have a tech drive with me so I could this time for sure let him hear the noise the car was making. He was intrigued and asked if I had some time so he could put the car up on a lift to see what this is. Said, done. After about 45 mins he came back to me and said that he knew where the noise is coming from, and that he would communicate to my service advisor about the right course of action.

A week or so later i have heard still nothing from BMW. So I decided to call in. Left a message for my service advisor (because 9 out of 10 times he does not pick up the phone). Anyway, I received the repair suggestion and estimate and I fell on my rear - $6000.00 to replace the differential/transmission ! Part cost: $1100. Labor cost: $4900. Why? Because the entire rear end of the car has to come out in order to take off the differential and replace it!

At first I ignored it, and thought oh well, I will just have to live with this noise for a while. But then things started happening, until at last the care would no longer go into Park! That was it then. Had to make the call. I decided to not go to the BMW dealer, but to my trusted local European car repair shop. They ordered the part and did the repair. Total cost including replacing motor mounts right along with it: $4800.

So I thought I was home free. But it was short lived. Whenever I would use my REX I kept getting error messages, ultimately resulting in the REX shutting down and getting the dreaded Electric Drive only message. WTF! One of the messages was some Overspeed error. So my mechanic and I kept thinking and thinking what it could be and he said that it possibly could be the camshaft position sensor. So I decided to swap it out, and got my next shock. According to the manual to swap out this sensor the following procedure is needed: Drop rear end out of car!!!! WTF. My mechanic was not going to have it and luckily he was able to contort himself to reach between the REX and the rear firewall and replace the friggin sensor. WOW. Unbelievably stupid.

I was all exited and hopeful that this would fix this issue with my REX.... but. Nope. No more overspeed error message, but the REX would still arbitrarily shut down while driving and in use. Then while driving deliveries one day I once again ran out of juice, and the REX would not come on. So I rolled into the closest Fast Charger. Hooked up to the DC charger but to my surprise ... nothing. It would not start charging. Ended up having to tow the car to BMW. They actually promptly started working on it. Then I received a phone call from BMW stating that in order for them to continue with the diagnosis I have to authorize $500 for them to a) remove my aftermarket CarPlay box that I had hooked up to the car, and remove NOCO 12 Volt charge leads from my 12-volt battery. That was $500 on top of their $300 diagnostics fee!. BTW, the reason why I had the charge leads on the battery in the first place was because I always had issues with the 12 Volt battery getting low. Had replaced and coded it several times over my 3 years of ownership. The last time was beginning of 2023, and when I replaced it that time I installed these NOCO charge leads for a NOCO trickle charger. Nothing bad. Have it on all my cars and basically eliminates alligator clamps.
The tech wanted it original. I said that I didn't have the $500 and that I am happy to come by and remove both items. Would take me no more than 30 mins. But they said no. I could either tow the care out of their lot, or they have to do it. Finally the rep said that $250 to set it back to original, and I said yes. I was kinda done with the whole thing, and agreed. Diagnosis: The 12-Volt battery was low and they bench charged it overnight and tested it and it was fine, put it back in the car, reset all errors and they said that my car is ready to be picked up the very next day!

I had my kids drive me there and drop me off. They left and I went inside, paid $550 to get my car. I had asked them to please hook the car up to the charger (since it was totally empty), however - they didn't do it. Total range of the car was 12 miles, and remember I still am not trusting the REX. So the stop 1 was the closest DC charger since their DC charger at the dealership was out of service! Go figure. So I pull into the closest DC charger, hook up, and .... nothing. It won't charge! WTF BMW. I had the car towed there because the REX wouldn't come on, and it wouldn't take a DC charge. So I limped the car back to the dealership. Barely made it. Went inside and told them that DC charging still does not work. Left the car there.... and went home.

The following week I get the phone call and they told me that it needs a new high voltage regulator. A part that is apparently a little box that is attached to the battery and handles the current for DC charging as well as REX charging. Repair cost: $3800. What choice did I have? None so I agreed and 2 weeks later I was back at the dealership to pay up and get my car. They said that they tested DC charging which worked and they tested the REX and had it running in service mode several times. No error messages, no issues. They also had a mechanic take the car home and drive it with the REX and they swore that there were no issues they could find. So I was once again hopeful that this issue finally has been fixed.

I drove the care home, but after the recent experiences I didn't have the balls to try out the REX. I just drove it home. The next day I worked up the courage to try out the REX and it actually worked. I was happy and thought that once again I could rely on my car. Boy was I wrong! I was out delivering in my car and had to turn on the REX for my last miles home. All of a sudden, REX shuts down and gave me Electric Drive only message and since I had no more range I coasted to a stop and had to call a tow truck. AAA told me that I had used up all my tows for this year and that I would have to pay this tow out of pocked and that the next tow they would not be able to arrange for me! WTF!!!!!! $300 later towing the car to BMW, they once again had my car. I was fuming. They did their testing and this time came back telling me that the 12-Volt battery must be faulty, and that they would swap it out under warranty since I just had purchased it from them earlier this year. They swapped it out and did some more tests and said that everything is working fine now and I could come and get the car.

Picked up the car and have not used the REX since. I just drive it under electric. Stopped going on delivery runs with the car and only use it for short distance commutes and it has been working since ... knock on wood. Of course, no REX, and I can not rely on my once reliable car. So sad. I reached back out to BMW and they said that there is nothing they can do. According to them Nothing is wrong with the car and everything is working. Until something else happens and they can find out the cause, this is what it is. So my REX is out of commission at least until next year when my AAA membership rolls - LOL.

Does anyone have had the same or similar issues? I really would like to get this fixed but don't have the money to arbitrarily start throwing money at it, like replacing the REX alternator/charger, which I am suspecting it is. Anyway, I would appreciate your feedback and maybe someone knows what causes this issue. I am about $10K+ in repairs for 2023, and the car is finally running and is drivable. I really don't want to sell it to a private party so that it becomes someone else's headache. And a dealer won't pay enough. Maybe a trade in, but still so much upside down in the car. Thanks for reading.
 
1: What year is the car?
2: You should not have put a lead on the 12v to "charge" it. The car will maintain the charge of the 12v even if it is sitting for days. If the 12v is discharging to the point it needs to be manually recharged, it is failing/failed OR you have some other part of the car that has a short in it causing it to drain continuously.
 
That’s a hard read, and expensive too.

I have had a similar situation a few years ago. Wife’s 2015 REx, just out of 3 year manufacturer’s warranty and the REx engine failed to start. Mileage would have been around 35k miles from memory, engine management light illuminated.

Local independent looked at it, fitted a new NOx sensor, but not really their speciality so paid their bill, few hundred pounds with the issue remaining. I reluctantly put it to our local BMW dealer, that was my first mistake.

Dropped car off and left it with them. They ring and say the car is fixed and to come and collect. Literally just out of the garage and the engine management light comes on. Straight back to the garage and take a courtesy car home.

They now say the NOx sensor fitted wasn’t correct, and would need a genuine part that there’s an issue with the fuel tank and fuel pressure sender which would need replaced also. £1k later and the car was apparently fixed. I collected and irritatingly they hadn’t charged it. On the way home I tried to switch the REx on and the engine management light came on and said unable to engage, battery power only. I’m roughly 10 miles from home, angry as hell with 5 miles battery range remaining.

Car literally broke down a mile from home. Switched off and on and managed to coax the remaining battery power out of it and limped home with hazard lights on.

Phoned the dealer the next day almost incandescent with rage. Their master tech tried to remote in using BMW software, but fruitless. Back to the garage for third time.

I’m spanner handy but no experience of electric cars, but figured it’s got to be a sensor or fuse or something and ask to speak to the master technician. I said I was a member of a BMW forum and he practically shut me down. They follow BMW service protocols and don’t enter into dialogue regards what it could be. I said to check the fuel pump relay, as it’s a known fault. He said he was a master tech and had never changed one to his knowledge.

Guess what it was, yes they swapped out the fuel pump relay and that fixed it. From that day on I’ve refused to let their technicians work on the car. Got myself ISTA dealer level diagnostics and have fixed everything from charging solenoid lock, PDA/PDC sensors, brakes, front wheel bearings, suspension top mounts, gaiters, drop links, etc.

I had a similar engine management light on recently, but suspect it’s something to do with wiring and moisture given the time of year. As belt and braces, I swapped out spark plugs as they were original and car was on 80k miles. The throttle body needs to come off which is an utter pain, as this was back in November with a head torch reversed into the garage at the house, desperately trying not to drop bolts.

Touch wood has been fine.

First thing to do is get diagnostics on it. I chased a PDA/PDC sensor for weeks. The fault tree can isolate the fault, you can clear codes and run real-time data. Try the fuel pump relay, that’s a relatively inexpensive part and given your miles, the sparks would be worth changing too. Also check HV cables (with it in isolation mode) to make sure there’s no moisture ingress. Again 12v battery can be problematic if original, but if that’s nearly new you can ignore.
 
I have not had any trouble with my rex, but despite this, it has taken me awhile to trust that the rex will work when needed. I recommend you code it for "hold state of charge" That way, you will still have significant electric range if the rex doesn't start, or stops before you are done with it.
 
2: You should not have put a lead on the 12v to "charge" it. The car will maintain the charge of the 12v even if it is sitting for days. If the 12v is discharging to the point it needs to be manually recharged, it is failing/failed OR you have some other part of the car that has a short in it causing it to drain continuously.
I agree!

During the pandemic, we drove our 2014 BEV only ~100 miles/month which was insufficient to keep the 12 V battery charged. When the "excessive discharging while parked" message was displayed, I would charge the 12 V battery with a battery charger. I attached a battery charger harness to the battery terminals to make charging easier just as MrL did. The original battery lasted over 7 years before failing.

MrL drives his i3 so much that the 12 V battery should never need to be charged with a battery charger as you wrote, unless he's doing something unusual to discharge the battery or something faulty is discharging it.
 
I have not had any trouble with my rex, but despite this, it has taken me awhile to trust that the rex will work when needed. I recommend you code it for "hold state of charge" That way, you will still have significant electric range if the rex doesn't start, or stops before you are done with it.
Did that the moment I bought it back in 2020. And it used to work like a charm. But not anymore!
 
So, I have been using my BMW i3 to drive deliveries for the past 3 years. Put a quick 115K miles on the car - boom. To me the car drives and sounds still like new, even though I have been side swiped and almost drove off an overpass - LOL. Anyway, while under warranty I kept hearing a clicking / grinding noise coming from the rear of the car. Had it at BMW 2 times and they were unable to identify where it is coming from. So, I kept driving it.

Over Xmas 2022/23 the noise came back. And got stronger. In February 2023 I decided to go back to BMW and have a tech drive with me so I could this time for sure let him hear the noise the car was making. He was intrigued and asked if I had some time so he could put the car up on a lift to see what this is. Said, done. After about 45 mins he came back to me and said that he knew where the noise is coming from, and that he would communicate to my service advisor about the right course of action.

A week or so later i have heard still nothing from BMW. So I decided to call in. Left a message for my service advisor (because 9 out of 10 times he does not pick up the phone). Anyway, I received the repair suggestion and estimate and I fell on my rear - $6000.00 to replace the differential/transmission ! Part cost: $1100. Labor cost: $4900. Why? Because the entire rear end of the car has to come out in order to take off the differential and replace it!

At first I ignored it, and thought oh well, I will just have to live with this noise for a while. But then things started happening, until at last the care would no longer go into Park! That was it then. Had to make the call. I decided to not go to the BMW dealer, but to my trusted local European car repair shop. They ordered the part and did the repair. Total cost including replacing motor mounts right along with it: $4800.

So I thought I was home free. But it was short lived. Whenever I would use my REX I kept getting error messages, ultimately resulting in the REX shutting down and getting the dreaded Electric Drive only message. WTF! One of the messages was some Overspeed error. So my mechanic and I kept thinking and thinking what it could be and he said that it possibly could be the camshaft position sensor. So I decided to swap it out, and got my next shock. According to the manual to swap out this sensor the following procedure is needed: Drop rear end out of car!!!! WTF. My mechanic was not going to have it and luckily he was able to contort himself to reach between the REX and the rear firewall and replace the friggin sensor. WOW. Unbelievably stupid.

I was all exited and hopeful that this would fix this issue with my REX.... but. Nope. No more overspeed error message, but the REX would still arbitrarily shut down while driving and in use. Then while driving deliveries one day I once again ran out of juice, and the REX would not come on. So I rolled into the closest Fast Charger. Hooked up to the DC charger but to my surprise ... nothing. It would not start charging. Ended up having to tow the car to BMW. They actually promptly started working on it. Then I received a phone call from BMW stating that in order for them to continue with the diagnosis I have to authorize $500 for them to a) remove my aftermarket CarPlay box that I had hooked up to the car, and remove NOCO 12 Volt charge leads from my 12-volt battery. That was $500 on top of their $300 diagnostics fee!. BTW, the reason why I had the charge leads on the battery in the first place was because I always had issues with the 12 Volt battery getting low. Had replaced and coded it several times over my 3 years of ownership. The last time was beginning of 2023, and when I replaced it that time I installed these NOCO charge leads for a NOCO trickle charger. Nothing bad. Have it on all my cars and basically eliminates alligator clamps.
The tech wanted it original. I said that I didn't have the $500 and that I am happy to come by and remove both items. Would take me no more than 30 mins. But they said no. I could either tow the care out of their lot, or they have to do it. Finally the rep said that $250 to set it back to original, and I said yes. I was kinda done with the whole thing, and agreed. Diagnosis: The 12-Volt battery was low and they bench charged it overnight and tested it and it was fine, put it back in the car, reset all errors and they said that my car is ready to be picked up the very next day!

I had my kids drive me there and drop me off. They left and I went inside, paid $550 to get my car. I had asked them to please hook the car up to the charger (since it was totally empty), however - they didn't do it. Total range of the car was 12 miles, and remember I still am not trusting the REX. So the stop 1 was the closest DC charger since their DC charger at the dealership was out of service! Go figure. So I pull into the closest DC charger, hook up, and .... nothing. It won't charge! WTF BMW. I had the car towed there because the REX wouldn't come on, and it wouldn't take a DC charge. So I limped the car back to the dealership. Barely made it. Went inside and told them that DC charging still does not work. Left the car there.... and went home.

The following week I get the phone call and they told me that it needs a new high voltage regulator. A part that is apparently a little box that is attached to the battery and handles the current for DC charging as well as REX charging. Repair cost: $3800. What choice did I have? None so I agreed and 2 weeks later I was back at the dealership to pay up and get my car. They said that they tested DC charging which worked and they tested the REX and had it running in service mode several times. No error messages, no issues. They also had a mechanic take the car home and drive it with the REX and they swore that there were no issues they could find. So I was once again hopeful that this issue finally has been fixed.

I drove the care home, but after the recent experiences I didn't have the balls to try out the REX. I just drove it home. The next day I worked up the courage to try out the REX and it actually worked. I was happy and thought that once again I could rely on my car. Boy was I wrong! I was out delivering in my car and had to turn on the REX for my last miles home. All of a sudden, REX shuts down and gave me Electric Drive only message and since I had no more range I coasted to a stop and had to call a tow truck. AAA told me that I had used up all my tows for this year and that I would have to pay this tow out of pocked and that the next tow they would not be able to arrange for me! WTF!!!!!! $300 later towing the car to BMW, they once again had my car. I was fuming. They did their testing and this time came back telling me that the 12-Volt battery must be faulty, and that they would swap it out under warranty since I just had purchased it from them earlier this year. They swapped it out and did some more tests and said that everything is working fine now and I could come and get the car.

Picked up the car and have not used the REX since. I just drive it under electric. Stopped going on delivery runs with the car and only use it for short distance commutes and it has been working since ... knock on wood. Of course, no REX, and I can not rely on my once reliable car. So sad. I reached back out to BMW and they said that there is nothing they can do. According to them Nothing is wrong with the car and everything is working. Until something else happens and they can find out the cause, this is what it is. So my REX is out of commission at least until next year when my AAA membership rolls - LOL.

Does anyone have had the same or similar issues? I really would like to get this fixed but don't have the money to arbitrarily start throwing money at it, like replacing the REX alternator/charger, which I am suspecting it is. Anyway, I would appreciate your feedback and maybe someone knows what causes this issue. I am about $10K+ in repairs for 2023, and the car is finally running and is drivable. I really don't want to sell it to a private party so that it becomes someone else's headache. And a dealer won't pay enough. Maybe a trade in, but still so much upside down in the car. Thanks for reading.
FYI Re: towing - I have AAA but I discovered that my insurance also provides it with slightly different limits. Because of the distance one would only tow me to my house, then I used the other to tow me to the dealership. This info might help someone else.
 
That’s a hard read, and expensive too.

I have had a similar situation a few years ago. Wife’s 2015 REx, just out of 3 year manufacturer’s warranty and the REx engine failed to start. Mileage would have been around 35k miles from memory, engine management light illuminated.

Local independent looked at it, fitted a new NOx sensor, but not really their speciality so paid their bill, few hundred pounds with the issue remaining. I reluctantly put it to our local BMW dealer, that was my first mistake.

Dropped car off and left it with them. They ring and say the car is fixed and to come and collect. Literally just out of the garage and the engine management light comes on. Straight back to the garage and take a courtesy car home.

They now say the NOx sensor fitted wasn’t correct, and would need a genuine part that there’s an issue with the fuel tank and fuel pressure sender which would need replaced also. £1k later and the car was apparently fixed. I collected and irritatingly they hadn’t charged it. On the way home I tried to switch the REx on and the engine management light came on and said unable to engage, battery power only. I’m roughly 10 miles from home, angry as hell with 5 miles battery range remaining.

Car literally broke down a mile from home. Switched off and on and managed to coax the remaining battery power out of it and limped home with hazard lights on.

Phoned the dealer the next day almost incandescent with rage. Their master tech tried to remote in using BMW software, but fruitless. Back to the garage for third time.

I’m spanner handy but no experience of electric cars, but figured it’s got to be a sensor or fuse or something and ask to speak to the master technician. I said I was a member of a BMW forum and he practically shut me down. They follow BMW service protocols and don’t enter into dialogue regards what it could be. I said to check the fuel pump relay, as it’s a known fault. He said he was a master tech and had never changed one to his knowledge.

Guess what it was, yes they swapped out the fuel pump relay and that fixed it. From that day on I’ve refused to let their technicians work on the car. Got myself ISTA dealer level diagnostics and have fixed everything from charging solenoid lock, PDA/PDC sensors, brakes, front wheel bearings, suspension top mounts, gaiters, drop links, etc.

I had a similar engine management light on recently, but suspect it’s something to do with wiring and moisture given the time of year. As belt and braces, I swapped out spark plugs as they were original and car was on 80k miles. The throttle body needs to come off which is an utter pain, as this was back in November with a head torch reversed into the garage at the house, desperately trying not to drop bolts.

Touch wood has been fine.

First thing to do is get diagnostics on it. I chased a PDA/PDC sensor for weeks. The fault tree can isolate the fault, you can clear codes and run real-time data. Try the fuel pump relay, that’s a relatively inexpensive part and given your miles, the sparks would be worth changing too. Also check HV cables (with it in isolation mode) to make sure there’s no moisture ingress. Again 12v battery can be problematic if original, but if that’s nearly new you can ignore.
Spartacus,

Please tell me more about "ISTA dealer level diagnostics". I would like to get the diagnostic equipment as well.
 
Spartacus,

Please tell me more about "ISTA dealer level diagnostics". I would like to get the diagnostic equipment as well.
This isn’t like VCDS for VW or Audi. That’s supported software from RossTech.

Basically buy it from EBay, search for seller with good feedback. You are looking for BMW ISTA Dealer Level Access Diagnostic Programming Coding, ENET & K+DCan Leads.

Ideally run this on an old laptop that can support, given you’re installing software from third party. Also, ensure the version you buy supports i3, model I01.

You’re running diagnostics only, avoid the programming version.
 
2024 LAUNCH X431 Elite for BMW OBD2 Scanner, Full System Diagnostic Bi-Directional Scan Tool, All Reset Services, ECU Coding, Battery Registration Tool for BMW/Mini/Rolls-Royce,Lifetime F-Ree Update https://a.co/d/eB6OJs8 Amazon
 
Thank you for the link to the Launch scanner. Will this scanner code the Hold State Of Charge HSOC on the i3 REx without Bimmercode (for USA editions)?
 
You don't need a scanner to do that, as I'm sure any number of YouTube videos will show you.
If your battery is 75% or less then you can go through a menu choice and force the HSOC option to start the Rex. At the last press before you enable that option, press and hold one of your eight programmable buttons. Then at any future point you want the function, just press your required 'button'.
Look on YouTube for exact menu options to get that point.
 
You don't need a scanner to do that, as I'm sure any number of YouTube videos will show you.
If your battery is 75% or less then you can go through a menu choice and force the HSOC option to start the Rex. At the last press before you enable that option, press and hold one of your eight programmable buttons. Then at any future point you want the function, just press your required 'button'.
Look on YouTube for exact menu options to get that point.
That would be great but I have never found one for USA sold cars
 
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