P0115 Code and other issues on 2017 XC90 2.0T T6 Topic is solved

kutzsche1 · Post by **kutzsche1** » 16 Apr 2023, 21:40

Hi, I have a rather odd problem on a 2017 XC90 T6 (2.0 turbo and supercharged). I have only 52k miles. Here are the original symptoms:
- For several months now, the car sounds like a diesel at idle, but not at load. So once you are driving, sounds normal and there are no noticeable issues
- About 6 months ago, I got a P0303 - engine cylinder 3 misfire code. I noticed nothing unusual, so I cleared it and it didn't come back.

The loud noise at idle bothered me so I did the following. I inspected and saw the rubber seal along the upper left motor mount was completely broken and I tested that under load, the engine rocked excessively. I assumed this was the source of the noise. I ordered the new redesigned part and replaced it. The engine doesn't rock anymore, so good, but noise remained.
- I thought, maybe I should change the spark plugs. it's only supposed to be at 70k but whatever
- I ordered from Amazon Champion Iridium plugs that claimed were a fit and installed them. I started the car, noise was still there otherwise seemed fine. I went on a test drive and within 100 feet the dashboard lit up and car went into limp mode. I immediately turned back. checked the codes - misfire on multiple cylinders. Ouch.
- I then searched the web and no one else said these plugs were the right fit. So I ordered Denso 3534 that multiple website recommended. meanwhile, I put the old plugs back ... and
- started the car and immediately got two new error codes P0111 and P0115. P0111 says "Intake air temperature sensor failure " and P0115 is "Coolant temperature sensor failure". WYF?! The car idled fine. I cleared both codes, started again and went for a short test drive. P0111 didn't reappear but P0115 would reappear over and over again after clearing and multiple engine off and on trials.
-I let the car sit 30 minutes and tried again, no issues, did a few minutes test drive, code did not come back.

So, I have multiple questions. How on earth can this be? These error codes couldn't possible be related to spark plugs?
Also, any idea what the "diesel noise at idle" maybe? And can incorrect spark plugs (I guess if the gap is wrong) cause misfire - I assume so. Shame for Amazon on selling me incorrect parts.

Post by **matthew1** » 16 Apr 2023, 22:53

Welcome to MVS, kutzsche1. You've got to gap the plugs. I'd check the owner's manual for the right replacement spark plugs either way. But always check the gap.

As for idle noise, you're on the right track thinking about motor mounts, although that new one didn't fix it. I'd look for anything that can vibrate... I had a vibrating noisy heat shield once because a bolt had worked its way out, allowing it to vibrate.

Is the noise when it's in D and you have your foot on the brake, or in P, or both?

kutzsche1 · Post by **kutzsche1** » 16 Apr 2023, 23:03

Thanks. I assumed spark plugs were pre-gaped. Anyway, the noise is at idle in either P or D. It almost sounds like when your muffler has a hole and starts to go ...
Any idea what the other wild codes were? Just a side effect of the incorrectly gapped plugs?

Post by **matthew1** » 16 Apr 2023, 23:12

Yes. They freaked out the ECU and it responded with codes. Just reset and forget.

I bet if you look around long enough for that sound with the car on and hood up, you’ll find it.

Post by **matthew1** » 16 Apr 2023, 23:14

Wear gloves and touch parts until you find it.

kutzsche1 · Post by **kutzsche1** » 18 Apr 2023, 22:09

I installed Denzo 3534 spark plugs and now it runs fine. I still have the idle noise though, can't find anything loose. I guess I let it be, since the car runs fine and throws no error codes.