Fixing a lemon, Trans Failsafe Prog

[Bimmernoub]

So i bought a 1998 BMW 740iL for next to nothing and i am determined to get it back to tiptop condition. I got it sight unseen and after driving it home it must have something wrong with the transmission.I would put my fut on the gas, the car would rev but i wouldn't go anywhere. I gave it some more gas It reved up really high and then the gear would catch and it would display what i can assume is the failsafe mode. The cluster is mostly burned out so i cant tell what it's telling me most of the time but i know when it goes into the failsafe mode (skips to 3rd). When i got it home i Checked the coolant and oil. The coolant was low and the oil was black. i added some euro blue and notice the coolant in the radiator was green. I flushed the radiator, thermostat was clogged, but i fixed (that and that's a story for a different day). My dad took it to a place to have the oil changed, i guess he was trying to surprise me, but the oil pan gasket needs to be changed and i have to ruin a good oil change. I took it to auto zone to have the check engine light checked; P0153, P0420, P0720, P0732, Bad O2 sensor, dirty cat, transmission speed sensor and gear 2 incorrect ratio. i do some slight digging and found a suggestion to change the transmission fluid. Changed the tranny fluid, filled her with Pentosin ATF1, the old AFT damn near black, four magnets had some metal particles, nothing worse then ive seen before, also found some chucks of metal, not very big, the biggest was a 3mm piece and again not the worst ive ever seen, but ive never changed the tranny fluid on a bmw before. When i went to test it again the car would actually role forward in drive instead of staying put. I eased onto the gas and drove like normal for a bit. I gave it some more gas and boom to the failsafe program. So i took it back to autozone and now i have P0731 and P0734 as well, gear ratio 1 and 4 now incorrect. I've done some more digging and found it could be everything from the battery to the whole tranny itself. I looked at my battery and notice it was a BMW battery, but im fairly sure it's not original because it doesn't have the "Miracle Eye", checked the fuses next to the tranny and noticed all of them had erosion on them, so i will go get those when i get paid again. I checked the main fuses and all those were good. It was late when i did this and i finally chose to make a post here and see if anyone here could help point me in the right direction. Thanks in advanced

[TheAngryBear]

Always measure voltage in these vehicles as they are very sensitive to low voltages. What would be fine in another vehicle is very bad in these. I just replaced my starter battery testing out at 12.5 overnight as it consistently (1 in 3 times) gave a non-start and trans failsafe.

Check those fuses and also check the harnesses.

Report back with the running voltage (alternator output) and either 1) overnight resting battery voltage or 2) results of autozone (or equivalent) battery test.


2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

[Bimmernoub]

I had checked my alt output on my lunch break; 14.05V and Max Load 13.95. Overnight resting voltage 11.95V. Didn't have anything to clean the fuses with so i'll pick something up on the way home and check them tonight.

[TheAngryBear]

I had checked my alt output on my lunch break; 14.05V and Max Load 13.95. Overnight resting voltage 11.95V. Didn't have anything to clean the fuses with so i'll pick something up on the way home and check them tonight.

11.95v?
https://m.youtube.com/watch?v=vxfi7XMS8pw
Unless it is 130F where you are you have a 0 state of charge on the battery. Even then it would only be 25% charged.
http://all-about-lead-acid-batteries...re-correction/



2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

[Indigo46n2]

Dont do what I did which is buy 2 batteries only to find out my alternator was bad. I permanently damaged the capacity of each battery in the midst of pulling fuses and reconnecting the battery constantly. If its reading in the 11s at rest or while disconnected, immediately consider a new or larger battery.

If your cluster isnt showing you any lights due to being faded or broken, thats a sign of another issue but one of the lights u might not be able to see could be your battery light on the far left above the CEL.

I have another post about this issue if u check the recents, same symptoms minus the OBD codes because I dont have a reader. A low voltage will cause this car to go possessed, and if your alternator is failing you will get a battery light which will lead to all sorts of systems failing due to improper voltage output from the battery while the engine is running. A failing alternator may read solid voltage for a half hour after startup like mine did, but it will eventually get tired and begin draining your battery thus reducing the capacity of the battery permanently.

Clean fuses, check voltage on battery with it disconnected and then connected. She should be 12+ at a minimum, 13-14 if shes feeling good, and 14+ at 2k+ rpm if your alternator is doing its job. Then if the car stays on long enough, check again 10 minutes later. Leave her running the whole time.

I witnessed the voltage of my brand new battery drop 2v in 5 minutes, literally watched as it decreased. At 11.66 volts you will get a Trans FailSafe which disengages the transmission for the most part and the car freaks out.

Currently swapping my alternator as we speak and this should at least help narrow down any further problems this car might be having like certain systems remaining engaged after the car is off that may cause unecessary draining from the battery or cause the alternator to overwork.