ORIGINAL POST 08/13
Hello! Looking for a bit of help on this; details below:
I bought my new (to me) Volvo back in April; it currently has just over 150,000 miles on it.
About two weeks after purchasing it, it started flashing the P0420 error code (Catalyst System Efficiency Below Threshold Bank 1). Admittedly (and possibly ignorantly), I had assumed this was an O2 sensor issue and had yet to fix it. I'm lazy, that is a problem. I looked through the "Eternal P0420" thread and think I have a lead on what I need to do to diagnose this further. I don't believe this is related to the misfires since my understanding is Bank 1 only addresses Cylinders 1-3 (I could be wrong; please correct me if so).
Just tonight, I started her & she had a low rumble & the headlights were gently flickering. Upon reading the codes, she flashed the following:
Confirmed:
- P0204 Cylinder 4 Injector "A" Circuit
P0304 Cylinder 4 Misfire Detected
P0420 Catalyst System Efficiency Below Threshold Bank 1
- P0204 Cylinder 4 Injector "A" Circuit
P0304 Cylinder 4 Misfire Detected
P0420 Catalyst System Efficiency Below Threshold Bank 1
- P0420 Catalyst System Efficiency Below Threshold Bank 1
P0896 Shift Time Too Long
I guess the guidance I'm looking for is whether this combination of errors could be a sign of greater issues. I am an eager-to-learn layman, so any help or opinions would be greatly appreciated.
EDIT 08/13:
She's still running a bit hot, so I'm going to take a run at the coils in the morning. In terms of the P0420 code, she was running well, and I didn't have any notable mileage issues, which is why I assumed (hoped) that it was just an issue with the sensor rather than the Cat itself. I typically get ~580 km out of a tank. I've been filling with 91 octane, but from my understanding, the previous owner was using 87 for the extent of the time he had her.
Tonight, after the misfire, she struggled to get to highway speeds promptly on my way home. I feel like it's just the spark plug, but again - I might just be stupid. Thanks in advance, folks <3
UPDATE 08/14:
Alrighty, so the trail continues. I swapped around the ignition coils between Cylinders 4 & 5, and the misfire was still on 4, so that was good - one issue down.
I replaced the spark plug for cylinder 4; nothing too crazy. Started her up & she was running fine until I brought her up to speed, and then the misfire was back. Damn It.
I had hoped this would be an easy fix, but alas. I'm looking at booking an appointment with my mechanic for a general checkup, but in the meantime, I'm going to keep working at this.
Any help/insight would be appreciated - I will continue updating this post as I go in hopes that I can save someone else some time in case they're in a similar situation.
UPDATE 08/15:
My best guess is that it's a fuel injector issue, so now it's just a matter of figuring out whether it's the part itself or electrical. I hope it's the part since that's an easier replacement, but we'll see. I have a buddy with a multimeter, so hopefully, I can recruit his charity tomorrow. The mechanic is booked for Monday, so worst case scenario, I just wait it out and pay someone more knowledgeable to finish up the legwork on this.
List of work done so far:
- Cylinder 4 & 5 Ignition Coils Swapped (No Change)
Cylinder 4 Spark Plug Replaced (No Change)
- Intake Pressure is marked as 62.6 kPa (Infocar Engine Diagnosis)
RE. is 55.8rpm/% (Infocar Engine Diagnosis)
Short-Term Fuel Trim: 0.23%
Long-Term Fuel Trim: -1.18%
Mass Air Flow: 10.4g/s
Average Engine Load: 25.3%