2000 S70 ETM/MAF diagnostics

[Caberguy]

I didn't have a helper on hand today to hit the throttle while I was watching. I did shoot some video of what happens when I pull and replace the fuse:



If you listen closely, you can hear multiple quieter clicks. I don't remember if I did this with the intake hose attached last time, that might have muffled these softer clicks when I tested it before, or the fact that I was on a fairly noisy street might have drowned them out.

Fairly definitive?

[precopster]

Why don't you rest the camera in the bay pointed at ETM (perhaps between the jaws of a clamp with rags to protect it) with video rolling then go back, turn on the ignition and press the pedal. Then you'll have a video of what it does when you press the pedal.

I can hear the rickety clicks at the beginning of the video. Sounds suss !! Still with no ETS light it's not looking like an ETM fault.

I've NEVER diagnosed an ETM as faulty without an engine code and/or ETS light and I've had about 70 of them come through my workshop.

[Caberguy]

I didn't have a ton of time yesterday, and I couldn't figure out a way to secure my camera (i.e. my phone) at the time. It shouldn't be too hard to figure something out.

[Caberguy]

Ok, it was pretty easy to prop up my phone. I tried it twice, same results. Key in position 2, foot to the floor, throttle plate opened right up. Here's some video (I did cycle the throttle twice on this one, it didn't just close and re-open on it's own). There seem to be some more extraneous clicks again when the plate opens the first time.

[Caberguy]

I just want to add that the ETS light does come on along with all the other lights when I first put the key in the ignition, so it's not just a burned out bulb or something. And the system has thrown codes when I've disconnected the MAF and the ETM to do diagnostics, so it seems to be working. And that I'm periodically checking for both stored and pending codes with an OBDII scanner, and not just relying on the CEL.

[abscate]

I think it's new MAF time...

[Caberguy]

The symptoms do seem to point to the MAF. I guess. Is there a better way of diagnosing it than measuring what it's reading, or unplugging it and driving (both of which I did, and both of which seemed to indicate that the MAF wasn't causing the problem).

I'd rather not just continue to throw parts at it with out a solid diagnosis.

That said, I could go with a used OEM for about $50, a new Bosch for about $90, or a new OEM which I've found one place at $160. What say you?

[regent]

...I'd rather not just continue to throw parts at it with out a solid diagnosis...

To 'solidify' your diagnosis, I would like to rule out possible power supply related problems (Engine Management RLY contacts and downstream circuits to include the ground to the ETM connector

[precopster]

Your MAF is a Denso brand NOT a Bosch and runs a different part number. Try tripling those prices for new ones.

Of course check and clean the earth/ground connection on the engine block near the oil pressure switch.

Look under the fuse panel in the engine bay and see if you have a SAS relay. I discovered that when one is fitted Volvo chooses to switch power to the ETM through this relay instead of the engine management relay and they burn oit causing power fluctuations to the ETM. However in all these cases a ETS light DID appear.

Your case may be there beginning of failure of this relay hence those rickety scratchy sounds upon first power up.

[regent]

Right on the money