Honda CR-V P0420
TL;DR
P0420 on the Honda CR-V signals reduced Bank 1 catalytic converter efficiency, most commonly from an aging catalyst or a lazy downstream O2 sensor, occasionally from an exhaust leak.
Why P0420 appears on the Honda CR-V
The CR-V is a high-mileage, long-lived SUV, and P0420 is one of the most frequently reported check-engine codes as these vehicles age past roughly 100,000 miles. The engine computer compares the upstream (front) and downstream (rear) oxygen sensor signals to judge how well the Bank 1 catalytic converter is working. When the rear sensor starts to mirror the front sensor, the computer concludes the catalyst can no longer store and process oxygen efficiently and sets P0420.
Model-typical causes and rough likelihoods
- Aging or worn catalytic converter (around 45%) — the most common root cause on higher-mileage CR-Vs, especially after many short trips or a past oil-burning or misfire episode.
- Lazy or failing downstream (rear) O2 sensor (around 30%) — a slow-responding sensor commonly mimics a bad catalyst and is far cheaper to replace, so it is worth testing first.
- Exhaust leak near the manifold or before the rear sensor (around 15%) — leaks let outside air skew the readings and are often reported after rust or a loose flange gasket.
- Underlying misfire, fuel-trim, or oil-consumption issue (around 10%) — unresolved problems can slowly damage the catalyst on some engines.
Owner tips for the CR-V
Before spending on a converter, have a shop graph both oxygen sensor waveforms and check for exhaust leaks and any stored misfire or fuel-trim codes. Clearing the code without fixing the cause usually only delays its return. Because P0420 rarely leaves you stranded, you can keep driving with caution, but fixing it promptly protects fuel economy and lets you pass an emissions test.
Summary
| Code | P0420 |
|---|---|
| Meaning | Catalyst System Efficiency Below Threshold (Bank 1) |
| Severity | Medium |
| Can I drive? | Yes, with caution — diagnose soon |
| Most common cause | Aging Bank 1 catalytic converter or lazy rear O2 sensor |
| Typical repair cost | $150–$350 (O2 sensor) to $900–$2,300 (catalytic converter) |
Full diagnostics
For the complete step-by-step diagnostic and repair guide, see P0420 — full diagnostics.
Frequently asked questions
Is it safe to keep driving my Honda CR-V with a P0420 code?
In most cases you can keep driving a Honda CR-V with a P0420 code in the short term, because it signals reduced catalytic converter efficiency rather than an immediate mechanical danger. The CR-V will usually run normally, but you should have it diagnosed soon: the fault will cause an emissions-test failure, can slightly hurt fuel economy, and may worsen if the underlying cause is a misfire or oil-burning issue. Avoid ignoring it for months.
What is the most common cause of P0420 on a Honda CR-V?
The most common cause of P0420 on a Honda CR-V is an aging or worn Bank 1 catalytic converter, especially on vehicles past about 100,000 miles. The second most common cause is a lazy or failing downstream (rear) oxygen sensor, which can mimic a bad catalyst but costs far less to replace. Exhaust leaks and unresolved misfire or fuel-trim problems are less frequent but real triggers, so proper diagnosis is important before replacing the converter.
How much does it cost to fix P0420 on a Honda CR-V?
Repair cost for P0420 on a Honda CR-V depends on the true cause. Replacing a downstream oxygen sensor typically runs about 150 to 350 USD including labor. Replacing the Bank 1 catalytic converter is the most expensive fix, commonly around 900 to 2,300 USD depending on whether an OEM or aftermarket part is used. Repairing an exhaust leak is often cheaper, roughly 100 to 400 USD. A proper diagnosis first can prevent an unnecessary converter replacement.