Transmission Fail Safe Mode

Clinticus · #1 02-13-2020, 04:30 PM

New BMW owner, new e53 X5 owner and new poster wondering if this issue has been solved in another post or forum if so please direct me to the proper location. When started cold X5 will shift through all gears and run smoothly at highway speeds. Once warm it will skip 1-3 and “thump” into 4-5 in both manual and auto driving causing trans fail safe. Here’s what I’ve done so far:
Replaced transmission cooler and thermostat, drained and filled trans fluid and replaced filter and gasket according to guidelines, replaced speed output sensor (P0721 code), replaced trans wiring harness (including temp sensor), drained and filled TC fluid, drained and filled engine oil and replaced filter (Valvoline MaxLife used for all fluids), drained and filled coolant according to guidelines (blue European 50/50), replaced power steering pump (was going out) and drained and filled fluid (MaxLife ATF), replaced fan clutch pulley (cracked from previous power steering pump being installed incorrectly), replaced MAF, cleaned ECM, about to replace B2S2 O2 sensor (P0440, P0057), engine average temp 103 C, trans average temp 95 C, battery average 13.4 - 13.6v running 3000 rpm’s. No longer pulling code P0731 now pulling P0733. Btw purchases vehicle 12/2019 with 144k miles and discovered most of these solutions from this forum so EXTREMELY grateful this exists! Hoping someone can assist with potential a solution other than a complete transmission rebuild!

crystalworks · #2 02-13-2020, 05:13 PM

First, welcome. And nice work so far. Second, you're going to need a scammer capable of pulling BMW codes. Will help you narrow your trans issue down.

Clinticus · #3 02-13-2020, 06:11 PM

Quote:

Originally Posted by crystalworks

First, welcome. And nice work so far. Second, you're going to need a scammer capable of pulling BMW codes. Will help you narrow your trans issue down.

Thank you SA,TX neighbor! Any recommendations on BMW specific scanners?

crystalworks · #4 02-20-2020, 01:23 PM

Quote:

Originally Posted by Clinticus

Thank you SA,TX neighbor! Any recommendations on BMW specific scanners?

Hey neighbor, once again I fail to look at the location of a poster.

The Foxwell should do most of what you need. Mine has gotten quite the workout from our BMW fleet. A rebuilt valve body combined with the 4 valve body seals + bridge seal will usually solve any problem with the trans. Usually. I am also going to have mine rebuilt this year by a company on Ebay that was recommended to me by a fellow local 4.8is owner.

First up though... finishing the E61 trans service and then the wife's E70 needs rebuilt valve body and seals. Hers is slipping out of gear on the highway though so fingers crossed it's not the E clutch bearing/bushing. That would suck. A lot.

Clinticus · #5 02-20-2020, 09:19 PM

Thank you all for the replies and suggestions! Replaced the front bank o2 sensors and was able to clear those codes. Waiting on the thermostat to be delivered tomorrow and another “fun filled” weekend under the hood! My hope is that this can be resolved without a tranny rebuild and plan to post a spreadsheet of parts, where they were purchased and price to hopefully pay it forward for others with similar issues. Will update with my progress after the weekend and look forward to her running as she should so I can move on to the FUN of upgrades rather than repairs!

andrewwynn · #6 02-13-2020, 05:53 PM

The shift to 4th is result not the cause.In other words, it's shifting into 4th because that what failsafe does.

Have you ever seen odd display of the selected gear in the dashboard? Eg in park, but no P, etc?

Often the cause of the failsafe is a dirty connector on the back of the transmission. It happened to me, and after I cleaned it, about 9 months later it happened again right after I got splashed with slush from a passing cat on the freeway. (I really need to seal that better; I think there's a design flaw that lets water come right through the center of the wire bundled).

Anyhow, on the 8 cyl I think the gear selector switch being external has a separate connector; either off those connectors get loose or dirty and it will give the exact symptoms you describe.

Voltage fluctuation from alternator will also kick the transmission into failsafe as well, and it can be just one momentary dip to cause it, so a real time reading with min/max voltage liked my fluke 87 will do is the best way to confirm or deny voltage dips

Clinticus · #7 02-13-2020, 06:15 PM

Quote:

Originally Posted by andrewwynn

The shift to 4th is result not the cause.In other words, it's shifting into 4th because that what failsafe does.

Have you ever seen odd display of the selected gear in the dashboard? Eg in park, but no P, etc?

Often the cause of the failsafe is a dirty connector on the back of the transmission. It happened to me, and after I cleaned it, about 9 months later it happened again right after I got splashed with slush from a passing cat on the freeway. (I really need to seal that better; I think there's a design flaw that lets water come right through the center of the wire bundled).

Anyhow, on the 8 cyl I think the gear selector switch being external has a separate connector; either off those connectors get loose or dirty and it will give the exact symptoms you describe.

Voltage fluctuation from alternator will also kick the transmission into failsafe as well, and it can be just one momentary dip to cause it, so a real time reading with min/max voltage liked my fluke 87 will do is the best way to confirm or deny voltage dips

Thank you for your response and the information. I did clean all electrical contacts with electronic cleaner during both fluid change and wiring harness replacement. Will check alternator voltage. What is the recommended mix/max range?

andrewwynn · #8 02-13-2020, 07:00 PM

It can't go below 12 for even 1/10s. Cleaning contact may not be enough. Just in the past week somebody couldn't start their car because the selector switch cable wouldn't stay latched.

Your said there's a hot/cold relation. A connector could be opening or sorting do to temp. Solder joints in the TCM. I would check all the connectors especial in the ebox and if no improvement, I would reflow the solder in the TCM

Clinticus · #9 02-18-2020, 03:14 PM

Update: Purchased a Foxwell NT510 based on recommendations in other posts and well worth the investment! Can now pull bidirectional codes that are BMW specific. Replaced both rear bank O2 sensors and now pulling codes for both front banks (which was to be expected) and the MAP thermostat which have been ordered and should arrive this week. Still going into limp mode however am optimistic that I’m getting closer to resolving this issue by replacing parts in need as well as correctly servicing the vehicle. Any additional advice/information is still welcomed and would be appreciated! Thank you all again.

andrewwynn · #10 02-18-2020, 03:40 PM

The foxwell will show real-time pressures of the transmission solinoid also the pins on the gear position switch. Make sure they are snapping clean into each gear position. What you describe is similar to when the contacts are dirty but the symptoms are identical to the position switch (incorrectly referred to as neutral safety switch) being faulty