05' V70 2.4L - Throttle body does absolutely nothing

samerooo · Post by **samerooo** » 26 Dec 2021, 11:41

Hi. I have a 2005 Volvo V70 with a 2.4L non-turbo. I purchased this vehicle with a bad engine and has the engine replaced with a good, low mile, used engine. The car is extremely clean and looks to be taken care of.

The engine fires up and sounds good. The idle is around 1100rpm. If you depress the gas pedal, it revs, but slowly and only goes up to around 2000rpm. Not enough to accelerate the vehicle and not drivable. Very low power. Also, when you rev it, in park or neutral, the revs will jump up and down constantly until the vehicle is turned off. Placing it into reverse or drive will make the idle stay constant, but still high around 1100rpm.
The throttle body never opens. I removed the intake tube and looked into the throttle body at the throttle plate while a friend depressed the gas pedal and it does not move at all.

I have tried to clean and lubricate the throttle body, no change.
Replaced the throttle body to the one from the donor engine, no change.
Purchased a known good used throttle body and installed, no change.
Replaced the MAF with 2 different ones, no change.
Double checked all grounds, checked fuses, checked all wiring is connected correctly, all hoses attached properly, no change.

Error codes: All codes were reset and these are what come back.

91AC - ECM-91AC throttle valve; Faulty signal (immediately after turning key to on position)

9918 - ECM-9918 throttle valve; Faulty signal (immediately after starting the vehicle)

2110 - ECM-2110 front heated oxygen sensor (HO2S), preheating; signal high (immediately after turning key to on position)

160A - ECM-160A throttle valve; faulty signal (after its been running for a few minutes

I have searched the internet and cant find a solution. I cant find any info on how to test this specific throttle body to make sure its getting the power it needs. Please help me.

Post by **chrism** » 27 Dec 2021, 07:00

A couple things come to mind. As far as the throttle errors, you may have a failure of the wiring between the throttle body and the ECU. That’s a fairly common problem especially the connector at the throttle body end, however a bad connection at the ECU end is possible - that one happened to me.

Another thing though is that you’re idling at 1100 with the throttle plate closed? That sounds like a bad intake leak somewhere.

samerooo · Post by **samerooo** » 27 Dec 2021, 08:06

Thanks for the reply. I forgot to mention that we removed the a bunch of stuff to triple check connections and found a hose under the intake manifold that was disconnected. We reconnected it, but I haven’t tested idle since, so that might be okay now.

As for the wiring, I was really hoping you wouldn’t say that. I checked the wiring and pins at the throttle body connector and all is great, so I’m guessing the wire might be broken somewhere else. Would you happen to remember the color of the wire I’m looking for? I can’t find a proper wiring diagram anywhere. Thanks so much.

Post by **chrism** » 27 Dec 2021, 10:33

In my case it wasn’t the wire connection itself that failed but rather dirt/corrosion/oxidation where the ECU pins plug into the harness.

Now that you’ve hopefully cured a bad intake leak, that may have also fixed your throttle errors. (ie: ECU saw a fast idle and tried to reduce the throttle plate opening which was already closed. Throttle body signals back “Hey I can’t close any more than I already am.”)

One can only hope that fixing that intake leak cures everything…..

Post by **abscate** » 27 Dec 2021, 11:03

Evan once had a complete nice PCV job and the idiot mechanic forgot to plug in his ETA. Then the guy actually called him from the road to tell him he had to plug it in. No wonder we work on our own cars.

samerooo · Post by **samerooo** » 28 Dec 2021, 14:44

chrism wrote: ↑27 Dec 2021, 07:00 A couple things come to mind. As far as the throttle errors, you may have a failure of the wiring between the throttle body and the ECU. That’s a fairly common problem especially the connector at the throttle body end, however a bad connection at the ECU end is possible - that one happened to me.

Another thing though is that you’re idling at 1100 with the throttle plate closed? That sounds like a bad intake leak somewhere.

I just checked on the wiring. I used my multimeter to check for continuity from the throttle body connecter to the ECU connector and all 6 wires check out. I also found zero corrosion. I'm not sure where to go from here. I was really hoping that was the issue.

So I have confirmed that the throttle body, MAF and wiring is all good. Battery is brand new. Does anyone have any more ideas? I would really appreciate it.

samerooo · Post by **samerooo** » 28 Dec 2021, 16:00

UPDATE: After I had everything disconnected and not finding anything wrong, I plugged the ECU and wiring back in, reconnected the battery, turned the car on and the throttle is working perfectly. Took it for a drive and its running perfect.
Very frustrating to be honest. I would have rather found a broken wire or something because now Im not confident in the vehicle and am scared of the issue returning randomly. Will update if anything changes. Will keep driving the vehicle short distances until I feel more confident in it.

Post by **chrism** » 29 Dec 2021, 05:43

There could have been some very minor oxidation on the ECM connector pins, such that disconnecting and reconnecting it “scraped” the pins clean and provided good continuity once again.

Good to hear it’s running well now.