'04 XC Engine Misfiring-Further Updated (Moisture ruled out - possible defective coils, bad MAF) Topic is solved

[chrism]

Volvo specialist thinks it may be a fault with the wiring harness that goes to the throttle body. He said he has seen them fail.

I agree the harness from the ECM to the throttle is known to fail and that could explain the throttle-related fault code(s). But what about the other, seemingly errant, codes?

Did you say you gave away your ECM removal tool?

[E Showell]

Yup. ECM removal tool now belongs to the MVS tool lending library.

Deliciously ironic.

[abscate]

I’m doubting a wiring harness failure vs a connector failure. These p2s have been around 20myears now , and Volvo wiring is far better than most any brand I’ve worked on , unless it flies

[E Showell]

Preliminary diagnosis from independent, factory-trained Volvo mechanic is electrical issue in harness or connector between ECM and throttle body. Should have a better idea along about Thursday.

Steve -- in my neck of the woods, we can't eliminate rodent chew-through as a cause of wiring harness issues.

[abscate]

Good progress, maybe order up some peppermint bags to repel rodentia

[E Showell]

Took him three minutes to make an initial informed guess as to what was up -- starting the car and being behind the wheel to observe, code reader and visual inspection of engine bay. Said only codes were throttle body related, which pretty much rules out an induction leak.

[- Pete -]

That was the next step I was begrudgingly approaching - contactless ETA(ETB, per Xemodex) and new wire harness (Theirs comes with the wire harness). I inspected my wire harness and connector at ETA & it was pristine and had no wire tension at the ETA connection. I then went with a new Bosch ETA from FCP, only to realize it wasn’t the problem at all.

https://xemodex.com/us/product/electron ... for-volvo/

Anyhow, hopefully your 04 is back in business soon. The ETA harness replacement will require the ECM/TCM to be removed. That’d be a good time to spray with contact cleaner & spray with dielectric grease. Do NOT allow anything to come into contact with the pins! But do test the car prior to installing the new harness. I’m really curious if your issue could be that simple of a fix.

Edit:
I spent a good amount of time reading about ETA failures & it is an extremely rare occurrence. ETM failures (01-02) on the other hand, are a well documented & frequent problem. What I’m saying is if you rule out every other possible thing and are left staring at the job of doing a new ETA harness, I would say get/replace JUST the wire harness IF POSSIBLE. That’s the hard part. Replacing the ETA is a piece of cake & very likely not needed.


Cable/harness only:
(Check with your local dealership also, lately I’ve found that they are often cheaper than most places online. For example a set of new Brembo/Volvo brake rotors for my V70R).

https://www.tascaparts.com/oem-parts/vo ... e-31409380

[E Showell]

I thought the failing throttle bodies were solely a P80 problem. I guess not.

[- Pete -]

Edited post above ^^^

[chrism]

I spent a bunch of money, including $350 for a new Bosch throttle body, only to eventually find the problem to be a bad connection under the ECM.

Consequently I have a spare throttle body sitting in a box - probably nothing wrong with it.

At the time this all was happening to me my local Volvo Indy said he had NEVER seen a Bosch throttle body go bad. I should have listened to him.