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Transmission Fail Safe Mode
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!
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2002 X5 4.6is Black Sapphire Metallic/Black |
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#2
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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.
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2005 X5 4.4i Build 04/05 Maintenance/Build Log Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles) 2006 X5 4.8is Build 11/05 Maintenance/Build Log Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles) 2010 X5 35d Build 02/10 Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles) |
#3
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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
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
#4
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Thank you SA,TX neighbor! Any recommendations on BMW specific scanners?
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2002 X5 4.6is Black Sapphire Metallic/Black |
#5
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Quote:
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2002 X5 4.6is Black Sapphire Metallic/Black |
#6
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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
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
#7
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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.
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2002 X5 4.6is Black Sapphire Metallic/Black |
#8
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Transmission Fail Safe Mode
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
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) Last edited by andrewwynn; 02-18-2020 at 03:47 PM. |
#9
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Transmission probably needs help
When my X5 ('05, 4.4i) started shifting wonky and going into limp mode, I went thru everything that could possibly cause the problem. In the end, I bit the bullet and replaced the transmission valve body with a rebuilt unit from RevMax. As you will see by studying this forum, X5's have a weak spot when it comes to the transmission mechatronics unit (what BMW calls the valve body). RevMax offers rebuilt units with upgraded solenoids that solve all the problems. While I don't want to tout RevMax, I just wanted you to know that they offer a solution that returned my X5 to like new shifting performance and I haven't seen limp mode since. I had it installed by my local indy BMW wrench and it was well under $2k
https://revmaxconverters.com/product...y-mechatronic/ AceEngineer
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2008 X3 3.0si My DD 2005 X5 4.4i Better Half's DD |
#10
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Quote:
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.
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2005 X5 4.4i Build 04/05 Maintenance/Build Log Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles) 2006 X5 4.8is Build 11/05 Maintenance/Build Log Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles) 2010 X5 35d Build 02/10 Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles) |
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