The Lemon IndexThe catalytic converter on bank 1 isn't cleaning the exhaust as well as it should. Full P0420 page
19 owner complaints · the #4 code Nissan Altima owners name · 8% of Nissan Altima complaints that name a code (every car: 2.3%)
Middle of 90,000 miles · most between 66,000 and 109,000 (15 owners gave it)
Nissan Altima owners named P0420 in 19 complaints to the U.S. government (NHTSA), most often on the 2002, 2003 and 2005 model years, at a middle of 90,000 miles. The part they name most is the catalytic converter (16 complaints). Complaints are owner reports, not proof of a defect.
Nissan Altima model years that report P0420
Owner complaints naming P0420, by model year. Raw counts: years that sold more get more complaints, so this is each model year's record, not a failure rate.
Mileage when it happened
90,000 miles is the middle of what 15 owners entered. Half were between 66,000 and 109,000 miles.
The mileage on the complaint form, when the owner gave one.
What owners say caused it or fixed it
The most-named part is the catalytic converter, in 16 of the 19 complaints (84%). 12 of those mention it being replaced or repaired. Next: engine (replaced or rebuilt) (3), oxygen (O2) sensor (2) and cam or crank position sensor (2).
- Catalytic converter16 complaints12 mention a repair or replacement · what Nissan Altima owners paid
- Engine replaced or rebuilt3 complaints3 mention a repair or replacement · what Nissan Altima owners paid
- Oxygen (O2 / air-fuel) sensor2 complaints2 mention a repair or replacement · what owners paid
- Cam or crank position sensor2 complaints1 mentions a repair or replacement · what Nissan Altima owners paid
12 complaints mention a recall and 8 mention a warranty.
Counted from the owners' own words: a part counts when a sentence names it with a cause or repair word. What owners wrote, not a diagnosis. A shop should confirm the cause before replacing parts.
Symptoms owners describe with P0420
68% of these complaints say the check engine light came on.
- Shakes, runs rough or misfires21%4 of 19 complaints
- Uses or leaks oil21%4 of 19 complaints
- Stalls or shuts off16%3 of 19 complaints
Share of the complaints naming P0420 whose text also describes each problem. A complaint can describe more than one.
Codes owners report with it
P0335 2
Other codes named in the same Nissan Altima complaints, and in how many.
Repair costs
Nissan Altima catalytic converter replacement cost · Nissan Altima engine replacement cost · Nissan Altima crankshaft position sensor replacement cost
Recalls on these Nissan Altima years
- Engine · 2002, 2005 · issued 2007
ON CERTAIN PASSENGER VEHICLES EQUIPPED WITH A 2.5L ENGINE, THE CRANKSHAFT POSITION SENSOR CAN OVERHEAT CAUSING A BRIEF INTERRUPTION IN THE SIGNAL OUTPUT FROM THE SENSOR. NHTSA 07V527000 - Engine · 2003 · issued 2006
ON CERTAIN PASSENGER VEHICLES EQUIPPED WITH A 2.5L ENGINE, THE CRANK ANGLE SENSOR IS AFFECTED BY TEMPERATURE VARIATIONS. NHTSA 06V242000 - Engine · 2002, 2003 · issued 2003
ON CERTAIN PASSENGER VEHICLES, THE CIRCUIT BOARD FOR THE CRANK POSITION SENSOR OR CAM POSITION SENSOR MAY HAVE AN IMPROPER SOLDER JOINT DUE TO SOLDER DEFORMATION CAUSED BY HEAT STRESS ACCELERATED BY THE EXISTENCE OF FLUX… NHTSA 03V455000 - Engine · 2002, 2003 · issued 2003
ON CERTAIN VEHICLES EQUIPPED WITH THE 2.5 LITER ENGINE, THE EXHAUST PIPE HANGER PIN MAY CATCH DEBRIS FROM THE ROAD THAT COULD BE IGNITED BY CONTACT WITH THE MAIN CATALYST. NHTSA 03V084000
4 recalls for the same systems (engine and exhaust) on the Nissan Altima model years above. A recall for the same system isn't proof it's behind P0420. Recall work is free at any dealer: check a VIN at nhtsa.gov/recalls or with our VIN check.
Keep going
- P0420: meaning, causes and every car that reports it
- Nissan Altima reliability by year
- 2002 Nissan Altima problems and recalls
Other codes Nissan Altima owners report
P0776 P0335 B0020 P0725 P0101 P0841 P17F0
P0420 on other cars
Kia Soul (80) · Ford Focus (16) · Hyundai Tucson (12) · Honda Odyssey (11) · Ford F-Series (10) · Honda Pilot (10)
The details
How we count
We read every owner complaint in the NHTSA file whose text names this trouble code, and count the ones filed about this model (matched by the make, model and model year on the complaint). Mileage is what the owner entered on the form.
Parts: a complaint counts for a part when one of the owner's own sentences names that part together with a cause word (failed, bad, diagnosed, caused by, leaking ...) or a repair word (replaced, repaired, new, reprogrammed ...). "Came back" means the same complaint also says the problem returned or the repair didn't fix it. These are counts of what owners wrote, not a diagnosis, and one complaint can name several parts.
Complaints are reports, not proof of a defect, and most owners never file one. Popular models get more complaints, so the counts are not a failure rate. The code meaning is the standard SAE J2012 definition in our own words, or the carmaker's meaning where we verified it for that make.
What P0420 means
The catalytic converter on bank 1 isn't cleaning the exhaust as well as it should. The car usually drives normally, but it can fail an emissions test.
Drive on, get it checked. You can usually keep driving. Have the code read at your next service or within a few weeks.
- Worn-out catalytic converter
- Faulty downstream O2 sensor
- Exhaust leak
- Misfires or oil burning that damaged the converter
Check the complaints yourself
NHTSA complaint numbers (search them at nhtsa.gov): 11073445, 10565192, 10486142, 10428549, 10427172, 10409132, 10405429, 10385061, 10379351, 10361043, 10326699, 10325907 and 7 more.
Quick answers
What does P0420 mean on a Nissan Altima?
Catalyst System Efficiency Below Threshold (Bank 1). The catalytic converter on bank 1 isn't cleaning the exhaust as well as it should. The car usually drives normally, but it can fail an emissions test.
Which Nissan Altima years have the most P0420 complaints?
In complaints to NHTSA, owners of the 2002 (9), 2003 (7), 2005 (3) Nissan Altima named P0420 most (19 complaints in all, 2002–2005). Raw counts, not a failure rate.
What fixes P0420 on a Nissan Altima?
Owners most often name the catalytic converter (16 of 19 complaints), then engine (replaced or rebuilt) and oxygen (O2) sensor. That's what owners wrote, not a diagnosis: have a shop confirm the cause with a scan and tests before replacing parts.
At what mileage does P0420 show up on a Nissan Altima?
Owners who gave their mileage reported a middle of 90,000 miles; half were between 66,000 and 109,000 (15 owners).
Can I drive my Nissan Altima with P0420?
Drive on, get it checked. You can usually keep driving. Have the code read at your next service or within a few weeks.
Sources: NHTSA owner complaints that name P0420 on the Nissan Altima, counted by The Lemon Index; NHTSA recalls; repair bills owners named. Meanings: SAE J2012 in our own words. Owner reports, not a diagnosis or repair advice for your car.