Had a friend fly in from Chicago this last weekend, wanting to see Yosemite in the autumn - which we did partially. But got stranded by the side of the road in "Engine SafeGuard Fail" mode - not exactly what they paid airline tickets for to see. :-( ... yes this was in an E39, but still same I believe M54B30 as in the face lifted Z's... in the E39 forums this seems to be an all too common failure. Though having been in this group for more than half of a decade, I don't think I've ever head of such here... my question is: are our M54's different from the ones in the 530i's? Or if they are the same - why does this failure and the apparent frequency of of happening in the E39 platform seem so different from my impression in an E36?
Is it DBW / DBC ? Any details on what failed inside throttle body? Just want to know what happened.
M54 should be drive-by-wire.
Fully DBW... I'm guessing the TPS or the air-temp sensor went away [the TPS because of temp issues; the temp sensor, just out of range??]... a clue is: that as long as the engine temp wasn't within the range that the temp gauge indicates "12 o'clock", that it would start and run without issue. It would still start, but not rev above 1500rpm if the engine was at operating temp. And if it was running, after some period of time, it would flash the "Engine FailSafe Prog" message, but as long as one didn't shut it down, it would continue to run, though the trans wouldn't kickdown for acceleration [ie, it was running on a limited power mode??]. ... but I believe this is exactly the same config/system we have in the M54 Z3's - hence the question here [but in fact wondering if this isn't the M54 that made it into the first gen Z4s, and hence why I've never seen any mention of this failure mode here ??].
Last edited by gmushial; 10-17-2018 at 02:03 PM.
Yes, all M54s use the same throttle assembly, though 2.5 and 3.0 use different sizes. Z3, Z4, E46/39/53, all the same. When it detects a problem, it goes to fail mode, which is throttle fully closed and all driving is done on the IAC. You can reach 25MPH with effort, according to my daughter.
You need to read the codes to see what's up.
/.randy
As always thank you... we limped into an AutoZone, had them read the codes: two too leans, bank 1 and bank 2; and a "replace the throttle body" code... I'm waiting for parts to arrive - replacing everything btwn air cleaner and intake manifold - it's 16 yrs old and since I'll have it apart, why not put all new parts back in. ... any idea why the Z3 people seem to see less of these than the E39 crowd? Heat under the hood more intense there, hence more cooked components??... and yes: about 25, or even 30 on a downhill :-(
Maybe it seems more common on E39s because they have other engines that have that issue too (M62's can also have TB failures) and the larger sample size of those cars overall as more were sold than Z3s. Its not a common failure by any means
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I think I'm viewing this more from a statistical perspective, ie, generally if one is a member of a forum, one has a single example of the vehicle that that forum represents, eg, each member here likely has a single Z3 (///M or otherwise) - with notable exceptions, yourself included... but what I'm noting here is that: I don't think I'd ever heard of a TB failure (now with the exception of Randy's daughter); whereas in the E39 group, with a lot of M54 engine vehicles, when one does a search, one finds threads upon threads about them failing, even to the extent that when I did such a search I found one member that had three fail in a year (before they ended up with one that has now lasted years since)... ie, there seems to almost be order of magnitude differences between there and here.
Yeah but of the Z3 forum members, how many of us have M54's? Most of us have M52, M52TU, S52 and S54's based on past collected data. Whereas MOST enthusiasts that have E39s have 01+ models as thats when BMW sold the most E39s as the 01 LCI was very desirable. 01+ also included all DBW engines in the E39 lineup so there are more there. And E39s are driven more whereas Z3s tend to be weekend cars
Not saying it doesnt or cant happen in a Z3 just sharing why it might be perceived that E39s have higher failure rates. A 1 in 10,000 failure will be seen much more often in a 5 series with 500,000 daily drivers on the road vs 20,000 Z3 weekend cruisers
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There is no code that says to replace the throttle body. There is no code that says to replace anything. All codes merely point to an electrical signal the computer flagged as suspect, and *sometimes* why it thinks it's suspect. in this case, there will be codes for the two throttle pots and their correlation, the stepper motor circuit, and the stepper motor performance. There are also codes for the accel pedal pots and correlation, as well as MAF vs throttle correlation. Not all of these are fixed by shotgunning a throttle body at it.
My daughters failure as in a M52TU E46. Different throttle assembly, same failsafe strategy. I have also had failures of my M62 E39.
I can't say for sure on the E39 vs Z3 thing. I quit the E39 forum years ago when it became apparent the value of diagnostic help was not based on logic or accuracy, but only the cost (the same thing has now happened to this forum.) If it is true, I would put it more towards driving style than the ambient conditions. Less throttle exercise. More use of C/C. More localized wear on a specific point of the throttle pots, or the quadrant gear. This is what happened to my 540.
/.randy
Regarding the E46 - I thought M52TU's had a cable linkage to act as a backup if that electronic failed. Does it still run off the ICV like on M54's or does it let you operate the throttle with the cable just running in "failsafe" mode?
I think's it's more of the 2nd scenario.
M52TU does have cable linkage, but it connects the pedal to a potentiometer on the TB. It's just a cable actuated drive by wire setup under normal conditions. If the electrical gremlins show up, the cable does actuate throttle via an internal spring (according to the E39 guys). How much? I have no idea.
Last edited by s8ilver; 10-18-2018 at 04:26 PM.
Nathan in Denver
1999 M Roadster, VFE V3 S/C, Randy Forbes Reinforced, Hardtop, H&R/Bilstein, Apex PS-7, Supersprint
1999 Z3 2.8 Coupe, Headers, 3.46, Manual Swap, H&R/Koni, M Geometry/Brakes, M54B30 Manifold, Style 42
RE M52TU. It is DBW. If it detects a problem, it will command the throttle to 0, and use the IAC only. The only way the cable would com into play is if the throttle control motor was disabled such that the computer can't control.. IE cut the wires. Any throttle pot error (which is by ar the common failure), and you will be limping the car home from your after-school job at 20-25MPH. Ask my daughter, she had to do it twice.
/.randy
Thank you, yet again. I was being a bit tongue in cheek w/re "replace TB" code... but that's what AutoZone's software came up with in translating code to message/action... but they are in the business selling parts ... I just went out and read the latest set of failure codes: 1632 and 0221, ie, TVA conditions not met; and TPS error... which I think translates into replace TB - though would be very interested in confirmation or disagreement with such. [When we limped back into Merced - they didn't read the 0221, but did have a pair of bank 1 and 2 too lean codes. ... but when I'm in there, and given how old the and crispy the rubber is: I'll replace the air clean to MAF and MAF to TB boots. Of note: at the side of the road I did unplug the MAF, and restart it, to see if that made a difference [was hoping, in that driving it back to civilization with the MAF unplugged is less daunting than in limp mode] - but that made no change.
W/re the E39 forum: I think we've all been spoiled here: given your knowledge/experience, your willingness to share, and a couple other people's - collectively make it a special group... and that's why I posted the question here - reading the technical know-how in the E39 group is like reading a 1970s JC Whitney catalog - bemusing at best.
- - - Updated - - -
At least my M52TU has such... not to say all do.
Just to follow up: did replace the throttle body and both rubber boots leading to it - 500 miles and two weeks later: no re-occurrence of the limp mode or any posted codes.
The replace was an hour and half job - basically one simply disassembles the air intake system back to the throttle body, along with loosening other things that are in the way, so that one can wiggle the old one out and the new one in.
Ordering and replacing the rubber boots was a good idea - even though the car only has 60k miles on it, it is 16 yrs old, and the old boots were rock hard [making unplugging the connections into them "interesting"]... with the new pliable boots: everything went back together trivially.
The only snafu was that one of the clamps that secures one of the boots disintegrated while removing it - and I had to replace it with a generic autozone clamp until the brown truck delivered its replacement. But all said and done, $130, including a new air filter, for a VDO branded TB, and the two OE boots, and less than two wall hrs from start to finish: and easy job and with very positive results. :-)
I think you can get the Z3 M52TU up to 55 mph or maybe even more in an IACV-related limp mode. Those times, I was able to pull over, restart the car, and gun it to avoid setting the fault that activated limp mode, once I got it warmed up. That was over a year ago, so I don't really remember the details beyond that it went away when I cleaned the IACV the second time.
I don't know if it's been said here yet, but don't listen to parts store employees when they try to diagnose the problems. If they were automotive technicians, they'd probably be at a repair shop instead of retail. Automotive diagnostics aren't that simple, and many technicians still have trouble with things involving electrical or electronics. In fact, my general observation with retail workers is that they know almost nothing about what they're selling, because most people don't like retail and it typically doesn't pay very well, but that was the only option they had for employment at the time.
Like Randy said, about all the codes can tell you is whatever deviations from "acceptable" conditions the ECU detected. You still need to double-check, examine, and diagnose the problem to identify what is causing the fault. The ECU can only share what it's observed and the rest is left up to the technician. In addition, you must consider what may have caused the part to fail. The codes provide you with clues as to which systems are likely involved, but might be multiple steps removed from the cause. For example, lean codes can be caused by vacuum leaks, restricted fuel flow, exhaust leaks, and inaccurate upstream sensor readings, as well as faulty O2 or AFR sensors.
Passing along my solution to TPS codes and engine failsafe prog on my e39: Clean and reconnect all connections to the throttle before spending money chasing gremlins! I went through 14 levels of hell trying to get my 2002 530i M54 out of engine failsafe program and faults 70, 71 and 73 for throttle potentiometer sensor. The solution was a loose connection on the backside of the throttle. That was it. The throttle connection seemed tight but wasn't. You have to remove the intake boot and DISA to get to it but these are easy. I removed the connection cleaned both male and female ends with electronic connection cleaner including the outside of the connection to ensure it seated properly. And jammed the s out of it until it clicked into position. Reassembled the various parts. and CLEARED ALL THE CODES AND ADAPTATIONS before turning on the engine.
Before you go and replace your Vanos solenoids, MAF, random cables, chasing vacuum leaks, wasting hours, etc., give this a shot... I'd hate for my two weekends chasing gremlins not help someone else!
What's worse is when the published wiring diagram doesn't actually match the car. I chased a fault on a Volvo I sold in March. Car just wouldn't start. Went through a whole 13 step diagnostic process on the Ignition Control Module. First 12 steps passed, and final step simply stated "check the ground wire." Ground wire in the diagram was labeled as white, and I had a white wire. Grounded it, no start. New module, no start. Then it dawned on me, maybe one of the two black wires was ground. Tested the big fat one...NO continuity. Grounded that wire and the car fired right up. That was a month of my time for one wire. I love cars.
At least the Z3 diagrams always seem to be correct.
Nathan in Denver
1999 M Roadster, VFE V3 S/C, Randy Forbes Reinforced, Hardtop, H&R/Bilstein, Apex PS-7, Supersprint
1999 Z3 2.8 Coupe, Headers, 3.46, Manual Swap, H&R/Koni, M Geometry/Brakes, M54B30 Manifold, Style 42
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