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Old 04-23-2016, 11:42 PM   #1
rikrobimmer
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FAIL SAFE MODE P0734, P0733 it's driving me crazy!

Hey guys I'm new in the forums but I've been reading them for a while. I have a 2003 325i. I love my car but it's been giving me a headache lately.

It started when one day I felt it weird, I knew something wasn't right and not 1 hour after I knew something was off, the car entered Fail Safe mode, I didn't knew what was that then. I looked for answers on the internet, it read to restart the car and I did. The Gear of Death dissappeared and the car was fine for like 5 minutes and then it went back to Fail Safe, but this time it didn't go away when I restarted the car. I made it home, and it was still in Fail Safe the next day so I took it to get inspected. It returned the code P0734 (4th Gear Ratio) my mechanic told me he had to do service to the tranny (change oil, etc) and so he did. 3 days later the car was ready, code free and Fail Safe free. The car ran perfectly for about a week and then boom, back into Fail Safe, I instantly used my scanner and it read P0734 again, but this time when I restarted the car Fail Safe was gone. It ran fine and then back again into fail safe, so I jumped into google and apparently there are a lot of things that can cause fail safe. It's important to say that the car doesn't feel weird, or has any weird noises at all. I know it's going into fail safe because the tranny starts slipping. I scanned so manny google sites without luck, and then I thought about my battery (it died 2 months ago and I replaced it with a Costco one, they said it'd fit my car) cause I read fail safe and tranny slipping can be triggered by voltage problems. Also it's important to say that my car was an aftermarket Android radio and Angel Eyes installed. So I decided to give it a try, I drove the car with the eyes and the radio turned off. It ran perfectly, not a single problem. NOT ONE. Then I decided to try and see if it was luck or if I was going in the right direction and so I turned on the Eyes, the car ran 200mts and it went into fail safe. I'm sure it's not a coincidence. I tested the car with the radio on, but with the eyes off and it didn't give any problems either. The I tested the car with the Eyes on and the radio on and yes the transmission started slipping and then it went into fail safe. So I bought a new battery, a bigger one that has the same specs as the OEM one. It ran perfectly today with the Eyes and the radio on, but then I decided to speed, I floored it and a few min later it went into fail safe returning the code P0734. It sometimes shows P0733 and sometimes P0734. This has only happened when the EYES are on. Do you guys think that something as silly as Angel Eyes are messing up or sending a weird signal? I'm gonna have the fluid level checked but it's new fluid so I'm thinking it should be good and it's too much of a coincidence that only when the Eyes are on the transmission slips and goes into fail safe mode.

Thanks in advance for your advice and help!
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Old 04-23-2016, 11:49 PM   #2
BMWCaptain
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Your angel eyes are drawing too much current and affecting your battery voltage.


First thing to do is take out the battery and get it fully charged.then reinstall it and test it.
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Old 04-23-2016, 11:53 PM   #3
rikrobimmer
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I literally bought the battery yesterday. I used the car today and it felt perfect, until an hour ago when it failed again. How does it work exactly (I'm not a car expert lol) with more revs, the tranny needs more voltage or something? Because it only happened today until I floored the pedal, but then again 2 days ago (with the "old" battery) with everything off, I floored the pedal and it was perfectly fine, until I turned on the Eyes. Thank you!
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Old 04-24-2016, 12:01 AM   #4
tefitzge
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If it's voltage and your battery is good... Maybe your alternator is going out or your voltage regulator.
Check voltage with and without the eyes on and see what you're getting.
I'm new here, but that just logic to me.
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Old 04-24-2016, 12:05 AM   #5
rikrobimmer
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I'm really really hoping it is voltage related, which I think makes sense with the tests I made. When I do the OBC tests without the eyes and the car running the battery is 141-140 .. with the Eyes on it's 140-138 and then it failed. Those are the old battery numbers, TBH I didn't perform the OBC test today cause I felt the car was doing great. I'll do the test tomorrow. Does those numbers seem fine?
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Old 04-24-2016, 12:20 AM   #6
tefitzge
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Not sure what you're measuring in. I'm assuming that's 14.1 volts dropping to 13.8 volts. That's a good reading in my book.
If you installed the new battery yourself, check your connections. Make sure they are right and corrosion free. Loose connections can cause issues too.
Not sure about BMW, but bad grounds can also cause electrical issues... Hopefully an E46 vet will chime in on that one.
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Old 04-24-2016, 12:21 AM   #7
tefitzge
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Battery connections are *TIGHT and corrosion free.
My phone loves to autocorrect me.
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Old 04-24-2016, 12:25 AM   #8
rikrobimmer
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Yeah that's what I thought. Everything looks fine on the battery. I read also that bad grounds can cause weird issues with BMW's so I'm thinking of removing the eyes. I'm gonna drive tomorrow with the eyes off and see if it works fine. If it doesn't.....then I think my problem is going to be bigger. I really hope it isn't.
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Old 04-24-2016, 12:27 AM   #9
tefitzge
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Good luck! I'm interested in see ok what it is. No doubt we will all have this issue eventually.
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Old 04-24-2016, 06:36 AM   #10
markusmarkus
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Check the engine ground strap and its connectors. It's located on the exhaust side of the engine at the front of the engine. You'll need to remove the plastic aero tray. It's a 0 gauge wire with brown insulation.

What's the maintenance history of the tranny? The fact that changing some of the fluid allowed the car to run fine for awhile tells me that the problem is with the tranny. The codes indicate that there's a mismatch in data streams from the tranny to the tranny control module. That is, the P0733 sez that "Gear 3 incorrect ratio." That means, IIRC, that a speed sensor in the tranny is either misreporting the tranny's speed (revs per second/minute) OR there's slippage in the tranny. The P0734 means the same thing is happening in 4th gear. Find a reputable shop that specializes in BMWs.
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Old 04-24-2016, 07:04 AM   #11
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NEW batteries are not fully charged when bought. You need to charge it with a charger to 12.6+ volts.

Then install it and see if you still have the issue.

Record your static voltage on the battery and report it back to us.
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Old 04-24-2016, 09:03 AM   #12
BKMrSteel
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Check all the grounds in the engine, and trunk. Who wired the halos, and how? They shouldn't do this if wired properly, I suspect something is wonkey.
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