OBD-II Code
P1273
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$5–$560
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P1273 on Toyota is A/F Sensor 1 Bank 1 Lean, set when the upstream wideband AFR sensor reports actual mixture leaner than commanded (lambda above approximately 1.05 sustained) while long-term fuel trim is already pegged near the +25 percent corrective ceiling.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP1273 on Toyota is A/F Sensor 1 Bank 1 Lean, set when the upstream wideband AFR sensor reports actual mixture leaner than commanded (lambda above app…
P1273 on Toyota is A/F Sensor 1 Bank 1 Lean, set when the upstream wideband AFR sensor reports actual mixture leaner than commanded (lambda above approximately 1.05 sustained) while long-term fuel trim is already pegged near the +25 percent corrective ceiling. It is the wideband cousin of P0171 and indicates the ECM has run out of headroom to add fuel and still can't reach stoichiometric.
Cheapest ladder
- do not replace the AFR sensor first.
- Pull live data and confirm Long-Term Fuel Trim at idle (a healthy 2GR or 2AZ should sit within +/- 7 percent; if LTFT is +20 percent or higher, you have a real lean condition, not a sensor fault).
- Smoke-test the intake from throttle body to head for vacuum leaks (PCV grommets, intake manifold gaskets, brake booster hose, and on 2GR-FE the upper intake plenum gasket are common).
- Inspect the MAF sensor for varnish (clean with CRC MAF-specific cleaner only) and verify MAF reading at idle (2GR-FE roughly 3.5 to 5.5 g/sec at warm idle, 2AZ-FE roughly 2.5 to 3.5 g/sec).
- Verify fuel pressure under load.
- The expensive misdiagnosis is replacing the AFR sensor (around $200) when the actual fault is a $4 cracked PCV grommet, a contaminated MAF, or an intake gasket that needs gasket dressing during reinstall.
Vehicle-specific patternsToyota 2GR-FE 3.5L V6 (Camry, Avalon, Sienna, Venza 2007-2014) sees P1273 commonly from upper intake plenum gasket leaks and from dirty MAF sensors a…
Toyota 2GR-FE 3.5L V6 (Camry, Avalon, Sienna, Venza 2007-2014) sees P1273 commonly from upper intake plenum gasket leaks and from dirty MAF sensors after K&N-style oiled-filter installs that contaminate the hot-wire. Toyota 2AZ-FE 2.4L (Camry, RAV4, Solara 2002-2009) sets P1273 frequently from PCV-side vacuum leaks plus the engine's known oil consumption that fouls the MAF over time. Toyota 1MZ-FE 3.0L V6 (Camry, Avalon, Sienna 1997-2003) sees P1273 from cracked intake plenum gaskets at the spider-style upper intake. Toyota 2ZR-FE 1.8L (Corolla, Matrix 2009-2018) typically sets P1273 from a torn intake boot between MAF and throttle body or a stuck-open PCV valve.
Estimated repair$5 to $560.
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