trans failsafe demon

[stefg]

Hi there,

I have a 2006 3.0i E53 and last weekend I had the "Trans Failsafe Prog" indicator light up along with going into limp mode. I was driving a 2 lane highway and hit the accelerator to overtake a semi. about 10 min later is when the TFP indicator lit up. I was out town so I took it to the nearest dealer. told me I had a crack in my air boot. replaced that and cleared the faults. running like a champ the rest of the day, then later that night it went back into TFP limp mode. so back to the dealer the next day. they tell me they cant duplicate the issue after clearing the fault. I think im good at this point. I make a 200mi trip back home with no issues. 2 days later im pulling out of work, as I come to a complete stop at the light... DING "TRANS FAILSAFE PROG"

started checking the forums and looked into a possible battery, alternator, VR problem. no issue there. I did have something funky happen with my brake lights earlier that day during lunch. "Check Brake Lights" lit up. took a look and the left were out, they didn't appear blown but changed them anyway. as soon as I get back to the office the "Check brake lights" is lit up again. take another look and this time the rights are out.

any ideas? are they separate or related issues?

thanks,
Stef g

[Gregory891]

Separate issues, you brake light issue is likely melted plastic posts for the bulb contacts in your tail lights. There is a BMW TSB on this (check the forum), they should fix this with some or lots of BMW help - a known issue. 98% of the time it's NOT the bulb.

As for the trans issue, how many miles or km? Have you ever had the fluid changed?

[TerminatorX5]

while it is possible for the fluids to act up, i suspect that the issue is more electric/electronic...

the tranny goes into failsafe when the various sensors can't match the RPMs of the engine to the RPMs of the tranny to the RPMS of the wheels...

the issue can be in the wheel speed sensors, in the ABS module, in the EGS module for the tranny, in the misfiring cylinder, when the DME cuts the power to a specific cylinder after so many misfires, when the crankshaft sensor is bad... the list can go on and on...
one of the things could be a MAF and/or throttle butterfly... those are simple, cheap fixes - and if they do not improve nothing, you are only out of about $10 total.. get the CRC MAF cleaner and clean the MAF - when you unplug MAF, see if the idling of the car goes for worse, better or remains unchanged... clean it anyways... if the idling did not change, you might have a bad MAF... idling should turn for worse for a moment and then, in absense of MAF signal, a standard value is provided, and the idle should improve... how is your external temp sensor - does show the actual ambient temperature in the cluster, or shows some weird value?

[stefg]

my x5 ha 915xx on the clock and have not had the fluids changed. the external temp reads good. took another look at the BMW service invoice and it states:

REMOVED AND INSTALLED GOOD KNOWN AIR MASS METER AND FOUND FAULT INTERMITTENT. PERFORMED FAULT MEMORY CHECK AND FOUND IDLE AIR FAULT STORED BY SEPERATED INTAKE BOOT.

I failed to mention in my previous post that I did get a "DSC INACTIVE" yellow brake indicator prior to each TFP, but pulling over and restarting the car cleared that. does this sound like more of a sensor issue? I want to take it to an indy this week. but also want to give them a good direction to start in to save time and $$.

[TerminatorX5]

the issue is intermittent, and as such is pointing either to a failing electronic component (a thermocompressed internal contact, not user-serviceable), a poor contact, which could be chaffed, nicked wire or corroded contact inside a connector, or if a component is permanently damaged/faulty, the internal systems substitute the value that is supposed to come from the component, and the car runs off that value, until the other, actual values from other car components shift enough to render the inflexible, static substituted value to be outside of the allowed range, and that is when the DME does not know what to use for the fuel/air mixture, the RPM sensors are out of whack, the other systems follow the trait.. in other words, the thing starts to avalanche, and starts setting fault codes in the memory that are secondary or even tretiary to main issue, that by itself may, or may not have its own code...

without hooking up the car to a diagnostic software it is impossible to tell with any certainty what is wrong with it...

if the MAF is good, or is thought to be good, you may have issues with a wheel speed sensor... there are 4 of them, one at each corner, and while all four are reporting the speed of each individual wheel, to determine many things, such as slippage of a wheel and other things, each sensor also is reporting for specific function inside the car...

i don't remember off the top of my head about which sensor responsible for which functions, but in absense of actual testing with the software, or with an O-scope, or at least with a multimeter, there is a slight chance to speculate which sensor is acting up based on the symptoms...

do a search on the google for the bmw speed sensors, there is an excellent write-up on bimmerfest, that had been referenced on this forum several times, that write up spells down the speed sensors and their functions... also, use the trifeca in your search, as the write up deals mostly with the lights on the dash caused by the ABS module and the speed sensors...

hope my rambling made some sense...

do you have a multimeter? do you know how to test a diode? speed sensor is a hall effect sensor, which is essentially a diode...

[upallnight]

Could be a simple thing as the brake light switch. I had the left rear wheel sensor go out which gave me an DSC/ABS/Brake trifecta but the trans program never popped up and I was able to drive the X with no problems.

Since you notice this problem when you went to step on the gas to pass a car I would suspect the speed sensor is not in synch or is bad and the computer is seeing that as slippage so in order to prevent the typical idiot BMW driver from destroying the trans by driving it while it is slipping, the computer place the trans in failsafe mode.