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Magneti Marelli ETM testing and diagnosis help

Do you have a failing Electronic Throttle Module? What steps to take if you do, plus the latest ETM news. Volvo 1999-2002 models only please.
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Year and Model: 2001 V70 2.4T
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Magneti Marelli ETM testing and diagnosis help

Post by prwood » Thu Dec 07, 2017 2:35 pm

My '01 V70 2.4T has an ETM with the following label:
Magneti Marelli ETM with Yellow Label
IMG_1209.JPG (70.84 KiB) Viewed 460 times
I am currently experiencing an issue with the following symptoms (please note, these are all from idling in the driveway; I have not yet tried driving the car):

1. After starting the engine, RPMs drop to between 500-750, there is rough, loud stumbling sound coming from the engine, and there is a rhythmic puffing sound from the exhaust (approx. five puffs per second).
2. If I increase RPMs to 3000, it will stay at that point, but has a dip down to ~2800 RPM once every second or so.
3. When I release the accelerator, RPMs drop down immediately, and as soon as they go under 1000, the stumbling returns. Sometimes it returns and continues until I shut the car off, other times the engine immediately stalls.
4. If I push the accelerator all the way down while idling, the RPMs increase over 3000, but after a few seconds they drop and the engine stalls.
5. Using an OBDII scanner, the throttle position is reported as 20% immediately at startup and while idling, and continues to report as 20% regardless of how the accelerator pedal is pushed, even though the engine does seem to respond to action on the accelerator pedal.
6. Also on the OBDII scanner, MAF sensor reading is 0.6-0.7. MAF sensor was replaced in January of this year and was just cleaned this week.
7. The car *has* had the Volvo Recall 155 ETM software update installed.

I am planning to remove the ETM from the car tonight in order to clean and inspect it. I have a few questions:

a. If I remove the ETM from the intake manifold, but leave it connected to the wiring harness, are there any functionality tests I can carry out?
b. Are there any tests I can run on the ETM using a basic multimeter? Other than the OBDII scanner, this is the only other diagnostic tool I have access to.
c. If I disconnect the ETM from the wiring harness, can I connect it to a 12v power source to do any further tests? If so, which ports do I use to power it?
d. I plan to clean the bore and throttle plate with air intake/throttle body cleaner and a nylon brush. If I were to also remove the sensor panels from the sides, and the inspection panel from the front of the ETM, and spray out the insides with mass airflow sensor cleaner or quick-dry electronic connector cleaner, would this be helpful or harmful?

Thanks for any advice you can provide.

Cars I've owned:
- 2015 to current: 2001 Volvo V70 2.4T
- 2007 to 2015: 2002 Subaru Legacy L Wagon
- 2003 to 2016: 2001 Toyota Corolla LE
- 1999 to 2003: 1994 Toyota Camry LE