Another Way to Diagnose a Bad ETM

[BobbyC]

Like so many here, I was experiencing hesitation and surging, but unlike many, I had no idle problems.

A trip to the dealer resulted only in a note that "No Codes; Throttle passed" and a suggestion I replace the MAF, Plugs, and Coil Packs.

I replaced the suggested parts (I bought 2 new Bosch coil packs and rotated through all 5 positions since all 5 had been replaced 30k miles ago, with no effect). I asked on the forums, and elsewhere, and no one had suggestions how to pin the problem down so the dealer would listen.

I have 2 scanners/code readers, one of which would record live data in table form, but it gave no really good clue what was happening from what I could see.

In desperation I bought an Autel MS-509 scanner that said it also would graphically display live data. It can be bought on Amazon for $109, or direct from China from "Deal Extreme" for $68 w/ free shipping. I hooked it up and was flat amazed. It produces beautiful live-data charts right on the screen for most functions*, and by watching the Throttle Position, Ignition Advance, and Air Flow, Load Factor live in chart form it was obvious that the throttle was jerking open/closed in pulsations that exactly corresponded to the surging/hesitation I was having.

I recorded the graphs (the screen shows a continuous 15 second record of what the systems are doing) using a "Flip" video camera in 3 minute segments and loaded the sequences (with my voice narration) onto a USB thumb drive that would play the videos on any computer and went back to the dealership. The Throttle Position (measured in %) looked like an EKG of an addict hooked on "speed" rather than a relatively smooth ramp up or down depending upon engine demand (as I used to compare to our other vehicles). The rpm plot showed the rpm varying by 200rpm while climbing grades (TC not locked up) or accelerating, and the Mass Air Flow showed corresponding variations, as did the Load Factor graphs.

It was like being able to take the service writer on a 10 minute test drive, but while highlighting the conditions that made the ETM malfunction the worst, rather than just a drive around the block to FEEL the effect (something he declined to participate in). They took me a lot more seriously the second time, and offered a free ETM cleaning, during which they said they found internal binding of the ETM not related to a dirty ETM, and that while a tracking test still showed the ETM w/in specs, the binding meant that the ETM could not respond to the computer properly.

Bottom line, I got a new ETM installed (and a thorough PCV cleaning), all absolutely free. The car that I'd grown to HATE driving is now a pleasure again.

I seriously doubt without the MS-509 I'd have had the confidence to be insistent, and I suspect without the "evidence" on video the service writer would have had the tech probe as deeply as he did. If nothing else, for $68 I have a diagnostic tool FAR more competent and capable than the Actron or Innova units costing over $200 (discounted street price). It's amazing what you can observe on a live chart that you won't see with freeze-frame data.

All this said, Volvo will STILL not replace the ETM unless in THEIR opinion (based on codes or examination) the ETM is BAD. You can almost forget the "death codes" Volvo uses to determine ETM failure. I had a very revealing talk w/ the folks at XE-Modem (REALLY nice folks, BTW) and they said the re-program Volvo did desensitized the computer to where the car has to be virtually undriveable before the codes will be displayed that authorize an ETM replacement.

I consider myself very fortunate to have gotten a free ETM, but I think the live graphs contributed enough to easily justify the expense of the unit. It will no doubt assist me in other "witch hunts" with my other OBD II vehicles as well.

Bob
*The MS-509 says it only will graph the PINs that display a "G" next to the PIN on the menu, but by accident I found at least on the Volvo, it will graph ALL functions, even those NOT displaying the "G."