Replacing ETM & TPS: fast oscillation on the bench?
 

Hello!

Sorry for the long post, but I figure the more information the better (might help someone some day).

ETM 8644345 white label died with an internal fault (ELM showed P0106) on V70 Bifuel CNG 2001 (B5244SG) manual. It got progressively worse with the limp mode, the usual stuff. The sensors showed 1.25...1.30V at default position, but the internal chip did not appear to respond to any commands. Instant limp mode whenever it is plugged in - even after disconnecting the battery for a while. (Btw, the car is in a pretty good condition under the hood. Only done 143k miles which looks to be correct. I think I was the last person on Earth with the white label that never got replaced under warranty.)

Hard to get the same one, so found a yellow label 8644344 that had been taken from a pure petrol model (specifically, from a B5244S of the same year) that was claimed to work, and I also ordered a Sacer contactless TPS.

As it is (without doing anything to it), the replacement ETM does not throw any codes whatsoever (!), drives more or less fine on petrol, but idles high (1500rpm) on both petrol and CNG, and has trouble staying on CNG after driving for a while. ELM OBD2 reports 12% TPS reading at idle and 65% at WOT. The white label reported 20% at idle and over 80% on WOT.

So I have the replacement ETM on the table, and whenever I power it up via green (+12V) and brown (GND) wires, the actuator and the plate start quickly oscillating between a default value and a value very close to it (at a rate of about 3...6 Hz), as if it is unsure which way to go. (The white label ETM stayed silent on the table.) Cleaned up the TPS pins and they show 1.31V and 1.35V at default position for the 5-pin side and 3-pin side, respectively, which seems to be within range.

I think I will try to replace the yellow label's TPS with Sacer if I know the ETM is not 'internally' broken, and then let a shop update the firmware (don't yet know, ECM or ETM or both? calibration? every action they do costs quite a bit). The yellow label seems to be in a much better condition overall, and it seems to be a logical choice between the two since it's supposed to be version 2.

I'm worried about the oscillation behavior though - why would it oscillate like that? The lab power supply shows the module draining 260mA at 12.2V while doing this (max is set at 1A), and this current seems to account for the actuator oscillation. Has anyone ever experienced this? I haven't energized it for more than 10 seconds as not to burn something up, though I am pretty sure I've heard the same type of clicking in the car for a longer time, and I've driven it about 10 miles so far with the new ETM to the garage and back.

The yellow label also allows to move TPS with key in position II, with an audible buzz, whilst the white label did not allow it.

Some numerical results

Yellow label behavior (high idle while the reported TPS% position is actually lower):

The oscillation/flutter I observe whenever 12V & GND clips are hooked up is very similar to the behavior in this video I found:
https://www.youtube.com/watch?v=ETNQavJ3-34
Doesn't look good :confused_smile:

VIDEOS. I've not yet fitted Sacer, been testing the ETM as it is. So on the car it doesn't look bad.
ELM says the range is 12.5% to 99.5% when tested with ignition in pos II. I would think default pos should be more like 20%? Maybe it cannot close when actually running, hence high idle?
https://youtu.be/B3Tk_qauMVc
I crosswired it to 1.34V/1.34V just in case.
The only code the ELM sees is about high idle speed.
Still oscillating on the bench, I have a feeling this might be related to the 0-20% range somehow.
https://youtu.be/2UUIGSG-Lxg

Sacer works fine except for the remaining high idle which is obviously not related to TPS, so basically it has been a preventive measure.
A dremel metal cutter is perfect for cutting the shaft to fit the magnet. A good Weller was used to solder it together making sure the solder has flown well in-between the pins. Used silicone to seal it, blocking off Sacer holes beforehand process with tape. I did not put much on top of the pins, so it would be a tad easier to remove it just in case Sacer needs to be fitted on another ETM (oh, the horror!). Cut out a new gasket for the ETM, and put a new MAF (Denso DMA-0113) and an air filter.

I'm going to try software update which may be just the last step in the process. Since the original ETM was the White label, the ECM knows nothing about the recall, the yellow labels, and all this Magneti Marelli guff. It's taking a red pill now... As a side note, software update prices are ridiculous.

The guy hooked up what appeared to be a VIDA/DICE programmer to the car, along with a 12V power source. After 5 minutes the firmware was updated and it started recognizing the ETM values, and idle speed changed from the erroneous value of around 1500 rpm to the normal range below 900 rpm or so. The update cost 100 eur (90 quid).

The replacement ETM also has what I think is a better return spring, since it has very limited jerk when I take foot off gas at 2500+ rpm (it's a manual). So check the motion of the flap, if it's not smooth and feels like it has notches, it could translate to jerking on descending rpm.