What P0420 means for your TLX
Your Acura's catalyst efficiency monitor detected the converter is no longer reducing emissions sufficiently. On the TLX, this is most commonly a slow degradation from carbon buildup (direct injection) combined with thermal aging. On V6 models, Honda's Variable Cylinder Management can also contribute by cycling cylinders on and off, producing uneven exhaust composition.
🎯 Top Causes on the Acura TLX (2.4L K24W / 3.5L J35Y)
🚗 Most Affected Acura TLX Model Years
| Year | Engine | Trim | Typical Mileage | Notes |
|---|---|---|---|---|
| 2015-2017 | 2.4L K24W (DOHC i-VTEC GDI) | Base, Tech | 90k-130k | 8-speed DCT models; carbon buildup primary issue |
| 2015-2020 | 3.5L J35Y (VCM) | V6, SH-AWD | 100k-140k | VCM cylinder deactivation contributes to oil burn |
| 2018-2020 | 2.4L K24W refresh | Base, Tech, A-Spec | 85k-120k | Updated cat substrate but same aging pattern |
| 2015-2020 | 3.5L J35Y SH-AWD | Advance, A-Spec V6 | 95k-140k | AWD adds heat soak in cat; can fail earlier |
⚠️ Is It Safe to Drive Your Acura TLX with P0420?
On V6 TLX models, Honda's Variable Cylinder Management (VCM) is a known cause of accelerated oil consumption that fouls the cat. If you bought used and the previous owner did not address it, consider installing a VCM Muzzler to keep all 6 cylinders active and reduce future cat damage.
🔧 How to Diagnose P0420 on a Acura TLX
- Check for misfire and lean codes. P0420 paired with P0301-P0306 or P0171 indicates a combustion issue feeding the cat. Always fix misfires and lean conditions first. Replacing a cat with active misfires destroys the new cat within 10k-30k miles.
- Run live O2 sensor data. Acura's HDS or any quality OBD-II scanner with live data: at 2,500 RPM warm, upstream O2 should swing 0.1V-0.9V quickly, downstream O2 should stay near 0.6-0.7V. If downstream mirrors upstream, the cat is failed. If it sticks at one voltage, the sensor is failed.
- On V6 models, check VCM behavior. With Honda HDS or a capable scanner, you can confirm whether VCM is cycling cylinders properly. Frequent VCM transitions plus oil consumption are a known cat-killing combination on J35-series engines.
❓ P0420 Acura TLX FAQs
Is P0420 covered under Acura warranty?
Federal emissions warranty covers the catalytic converter for 8 years/80,000 miles. Acura's powertrain warranty is 6 years/70,000 miles. Check your service history with the Acura dealer for warranty status.
How much does P0420 repair cost on an Acura TLX?
Diagnostic and minor sensor replacement: $200-$400. Full catalytic converter replacement: $900-$1,800 depending on whether OEM or aftermarket and which engine (2.4 inline-four versus 3.5 V6).
Will VCM disable solve P0420 on my V6 TLX?
A VCM Muzzler can reduce future cat damage by preventing the cylinder deactivation cycles that contribute to oil burn. It will not fix an already-failed cat but may extend the new cat's life.
Can I drive my TLX with P0420?
Yes for a few weeks. You will fail emissions tests but the car drives normally. Address within 30-60 days.
Does Acura have an extended emissions warranty for TLX?
Federal 8 year/80k mile coverage is standard. No TLX-specific extension has been announced for catalytic converters.