What Does "Trans. Failsafe" Mean?
If you drive a BMW with an automatic transmission, you may have experienced the dreaded “Trans. Failsafe” warning on your dashboard. It’s a warning that has become synonymous with vague problems and expensive repair bills. But what is it?
In this article we’re going to explain the "Trans. Failsafe Prog" warning, and look into the possible reasons you might be experiencing it.
What Does Trans. Failsafe Prog Mean?
Understand exactly what is happening when trans. failsafe lights up on your dash.
Very simply, this warning means “Transmission Failsafe Program”, a feature that only applies to automatic transmissions. Failsafe mode can come with a number of different labels such as;
They all mean the same thing, and that thing is that the computer in your vehicle has noticed something isn’t quite right and has decided that your transmission is at risk as a result of whatever has gone wrong.
The most typical manifestation of a transmission in failsafe mode (other than the dashboard warning) is the transmission being locked into one forward gear, unable to change shift either automatically or manually. The actual gear it will stay in varies from transmission to transmission, but it tends to be second or third gear.
Depending on the reason your transmission has gone into failsafe mode, you may be able to turn the engine off and back on and drive normally for a time, perform a vehicle-specific reset, or you may need a technician with specialist diagnostic equipment to plug into your car’s computer and turn failsafe mode off that way. Regardless, there’s a very strong chance that whatever caused your transmission to go into limp mode is still there, and you’ll have to get that fixed to prevent your vehicle going into failsafe again.
Failsafe mode can also be displayed in a number of ways across different vehicles. Some vehicles have the “PRND” light on the dashboard (standing for Park, Reverse, Neutral, and Drive) flash during failsafe mode, meanwhile others simply light up a transmission symbol or cog. Some older vehicles give no obvious sign at all, leaving the driver to guess from the fact that the vehicle is no longer changing gear.
Why Is There a Failsafe Mode at All?
What is the trans. failsafe mode FOR? Let's find out.
If you’ve ever used a spacesaver spare wheel, or temporary radiator leak fix, you’ll understand the principle behind failsafe mode. The idea is to allow you to get your vehicle home or to a repair shop so that it can be repaired whilst also minimising any damage caused by the fault.
It is intended to be a purely temporary measure to save you the inconvenience of being stranded when a transmission fault develops, but you would find it hard going to drive for any significant length of time or distance in failsafe mode.
What Should I Do If My Vehicle Goes Into Trans. Failsafe?
So your car is in trans. failsafe mode. Now what?
As mentioned above, the point of failsafe mode is to allow you to drive your vehicle to a place it can be repaired, or stored until repair can be undertaken. That’s what should happen in principle. In reality, however, you should gauge your situation carefully.
When a transmission is locked into a single gear, driving in certain ways can exacerbate the problem, potentially leaving you with a car that won’t drive at all. If your vehicle has locked into a lower gear—such as first or second—then your speed will be limited as attempting to drive too fast will result in the engine over-revving. It should go without saying that driving a regular car with the rev counter in red for any significant length of time is not advisable. If your vehicle has locked into a higher gear, however, you’ll be able to achieve manageable speeds but stopping and setting off will be problematic. An automatic vehicle should be capable of setting off in third gear, however every time you do, you degrade the internal clutch plates of the transmission at a much greater rate than during regular driving.
With this in mind, you should first try determine whether or not your vehicle has defaulted to a higher or lower gear. Next, think about how far your intended destination is, and what kind of route you’ll be taking. If you were hoping to drive home but home is a long drive away, consider finding a more local repair shop and taking the vehicle there. If your car is stuck in a lower gear, try to avoid motorways/freeways as you’ll be revving your engine to dangerous levels and still not going anywhere near fast enough to safely drive on that kind of road. Conversely, if your car is stuck in a higher gear, avoid routes that will involve a lot of stopping and starting (such as busy town centres), putting undue stress on the clutches. Wearing the clutches down like this for too long can result in them breaking down and essentially clogging the transmission up, resulting in a loss of drive at best, and a large bill for a complete transmission overhaul at worst.
What Causes Trans. Failsafe?
Why does it happen? Let's find out.
This is a tricky question to answer. The "Trans. Failsafe Prog" warning is a little bit of a “catch-all” solution in that, anything that the computer in your car deems a potentially damaging threat to the correct operation of your transmission will cause it go into failsafe.
For the sake of brevity, we will count any faults within the transmission itself as one thing. If you want to learn more about automatic transmission failures, check out this article on troubleshooting automatic transmission problems, but for this article the transmission is a single component.
Aside from the transmission itself, there are many components that can cause a vehicle to decide to go into trans. Failsafe. The computer that decides when to change gear takes information from a number of places in order to calculate when the transmission should change. This data includes obvious places such as the vehicle speed sensors and the gear shifter position, as well as less obvious components such as air flow pressure and inclination. If any of these readings are inconsistent or missing, it could cause the transmission to go into limp mode.
Another more insidious cause is that of failing electronics. Things like faults in the instrument cluster (where your warning lights and speedometer is), blown fuses, and even a failure in the transmission control module (the computer that controls the transmission) itself can all cause trans. failsafe.
Unfortunately, there really isn’t much you can do with an automatic vehicle that’s gone into trans. failsafe. Try turning the engine on and off to see if you get regular drive for a time, but if that works do not assume the problem is gone for good, because it almost certainly isn't.
The best thing you can do is get it to a technician with as little driving as possible, and let them plug their fancy diagnostic equipment into your car to find out why it’s gone into fault mode. Then take it from there.
If you've experience "Trans. Failsafe Prog" before, did you...
© 2016 John Bullock
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