Skip to content

BMW Automatic Transmission Fail-Safe or Limp Mode Warning Light

February 27, 2013

This answer is applicable for many BMWs in addition to the one listed below.

Q
car year: 1997
car model: 740iL
Hi Otto, I have been watching your videos on YouTube very help full. I have a question what does this mean (trans failsafe prog) can you help me Thank you very much for your time

A
BMW has been using electronically controlled automatic transmissions in most models since the late ’80s.  These transmission systems employ a transmission control unit which controls electrical solenoids to manipulate the various control and shift valves and functions in the transmission valve-body.  When the transmission control unit detects a problem that it “thinks” could be damaging to the transmission or engine, it goes into a fail-safe or “limp” mode. In this mode, the transmission will function in reverse normally, but in forward it will operate in only one gear (whether you have the shifter in D, or any of the lower gears). This will typically be 3rd or 4th gear, depending on the model. It will start in this gear and stay in this gear with no shifting. You would experience this as sluggish acceleration and higher than normal engine speed at about 40-mph and above.

If you must drive the vehicle when the transmission is in the fail-safe mode, accelerate gently and keep the road speed lower than full highway speed.

Earlier models do not employ fault codes and must be diagnosed manually.  Late models do employ fault codes and a diagnostic/scan machine can be used to check and read the faults to assist in diagnostics.  Note that this is not your common OBD-II engine management fault code tool.  This is what A BMW dealer or a properly equipped independent shop would have for full vehicle system diagnostics and coding operations.

4 Comments
  1. John Blazys permalink

    I have a transission question for a 2000 540i. I just changed the transission fluid but occaisionally, the shifting is hard and jerky but goes away.
    What could be the issue and repair?

    140,000 miles on this vehicle.

    • Otto permalink

      John,
      Did you set the fluid level with the engine running and the fluid warm?

  2. Martin Caspa permalink

    Good information.
    Yes you have described or given an overview of what happens when you are experiencing the Transmission in failsafe mode.
    But what is or are the possible solutions and outcomes if this mode does not reset.
    1.Does it reset at all any time
    2.what do you need to do to take care of this
    3 does it mean your transmission is gone and you need a new one
    4. What other critical symptoms are expected driving in this mode

    • Otto permalink

      Martin –
      1) As long as the fault (that caused the fail-safe in the first place) is present, the waring and the fail-safe mode will be present. If the fault is no longer detected, the fail-safe will cease and normal operation will return.

      2) In order to properly diagnose a transmission fault warning, the vehicle must be diagnosed using the GT-1 diagnostic system (or applicable similar system) to read exactly what the fault code is. Note that a common OBD-II engine management code reader tool will not read the transmission codes.

      3) No. The fault may be just a failed electrical valve control solenoid, for example. Granted, many shops, these days, will indeed just tell you that you need a new transmission. However, this would rarely be the case if the fault light is on. The most common issues would be within the transmission control hydraulic valve body, the transmission controller or other electrical control issues.

      4) Driving the vehicle when the transmission fault warning is on, can be fairly harmless (if driven gently) or may cause additional damage. It all depends on the root cause of the warning being on. If the vehicle seems fine in all operation, with the exception of no shifting when driving forward (as described in the post), the vehicle may be perfectly fine to drive until diagnostics and repair can be made.

Comments are closed.