Shifting problems

[Cboder218]

Walk through of my problem. Pre facelift 98 740il. Open door, P lights up on center console (normal). Put key in the ignition turn it. D lights up on the dash and goes out after a second. Car wont start. Cycle key and it starts. I can see PRND32 on dash but non of them are lit up. Car starts. Try to switch into M but wont. Hard shift into reverse. Put it into D and its stuck in 3rd or 4th gear. No trans failsafe message. Center console lights up the correct PRND32. I removed and cleaned neutral switch on trans. Swapped the shift plate on council even though it worked fine. Same thing. I had battery and alternator tested and they are up to spec. I only have a cheap code reader that only pulled my 02 sensor codes (Doing them tomorrow). What could it be? Computer? Ignition switch? Maybe the neutral switch is just bad and I should get a new one? Fuse? Time to rebuild trans?

[Cboder218]

Link to youtube showing my problem i figured it could help you guys!!
https://youtu.be/mmw_-UR9v58

[Mayorchuck]

That's a new one to me. It's probably something electrical though. If it were mine, I would check the connections of the Transmission Control Module in the ebox to make sure there is no corrosion there.

Actually, I would probably first try a battery nap. Pull the battery cables off for 10 minutes, touch them together for a minute and them put them back.

I've never seen the iggy switch cause anything like this but nothing would surprise me though. Any other signs such as horn/radio not working? Visor test?

Beyond that, trans position switch may just be bad as you say. I sent a note to Tim (meeknet) to see if he has experience this before.

[Cboder218]

Thank you for the reply along with any and all help i can get. I already have done the battery nap after pulling and cleaning the neutral sensor and when i swaped out the the console plate. Even though the battery tested good and fully charged i put it on a 2 amp charger with auto shut off over night knowing how picky these cars are when it comes to battery juice. I will check the connectors at the computer tonight. I will update with what i found. If that does notnfix it than On Monday i am going to have the only shop in town that works on these cars scan it for me and i will post the codes if there are any.

[acspecialists]

I had some weird stuff happen on my trans. Looked up Timm's method for cleaning the switches and it has been work fine since then.

https://www.meeknet.co.uk/e31/timms_...e_problems.htm

[Cboder218]

Also radio, horn, sun roof, visor lights work fine. Visor test done with no problems. All fuses checked. I did find a blown big 50 amp under the hood replaced that it didnt seem to change anything at all. There is only computer left in the ststem becides trans it self but being there is no trans safe message i know it has to be electrical. I do have check brake light and check tail light but all lights except the 3rd brake light work. Also when i first got the car like 3 months ago. The license plate lights did not work the wires in the trunk loom where good. And being in a rush to fix it i just put a jumper wire from running light on rear right tail light. Could the lcm cause this issue with out having the other known problems? Once again thanks to everyone who can help me.

- - - Updated - - -

I was just reading that same post. Haha i will try it tonight along with checking both lcm and trans computers and let everyone know what the outcome is. Once again thanks for all the help already.

[Timm]

It does seem like a selector problem - there are some switch combinations that DON'T bung up TRANS FAIL-SAFE PROG but also stops the gearbox working correctly. On the E31 you get a strange display of S3 - but that isn't available on the E38 - so, if you have INPA (or Carsoft) then check the 'wires' section of the gearbox diagnostics against the codes shown below:



If the codes are correct (but I doubt it) let us know and we'll have another stab at it!

https://www.meeknet.co.uk/e31/timms_...e_problems.htm

[Cboder218]

I do not have INPA or car soft yet. But i was thinking about getting this. What do you guys think about it? I like the codeing option as there is no one around my area that does coding.

http://vi.raptor.ebaydesc.com/ws/eBa...=0&cspheader=1

I already have a laptop i can put it on. So i am going to take out and clean the Neutral switch like the link says. At the same time check the trans computer and the lcm connectors for corrosion. If that dont fix it i will just buy a new safty switch. Worse case i have an extra in my tool box. Although there is a 98 740il in the scrap yard with 160k they want $500 for the transmission. So i am debating $300usd for a sensor or $500 for a working transmission with the sensor. Being my car is at 260k miles i dont think it would be a bad idea to have an extra trans around.

[Cboder218]

So i cleaned the sensor as link says no difference was made. But being bored i was messing around in the cluster test 14 and got codes that seem to be related to the cluster going bad. 1: cf 82 0002: 90 84 000 3: bf 88 000 4: 3f 88 000 5: 8d 90 000. Could a cluster going bad cause this issue with the trans?

[Mayorchuck]

No. You really need a proper diagnosis to see where the communication is failing before you start buying parts for it.

[Cboder218]

You are very true. I am going to get one friday. I miss driving it. As soon as i get one i will report back with what i figure out. I want to post the fix for anyone in the future who has this problem. I think its the safty switch truthfully. But i will wait for the scanner to make sure.

[Timm]

With diagnostics you can check if the gearbox selector switch is sending back the correct switch combinations on the WIRES page - it's either right or it's wrong!