P21A3 code meaning
Cylinder 8 Air-Fuel Ratio Imbalance
Powertrain system Generic code P21xx codes Check engine light
What P21A3 means
P21A3 blames cylinder 8, on a V8 the last cylinder in the numbering. No manufacturer documentation of this code is publicly available, and no bulletin in the NHTSA index refers to it; the basis is the general CARB requirement for detecting cylinder imbalance, phased in for 2011 to 2014 model years with an emission threshold of 3.0 times the FTP standard (4.0 for SULEV II) until 2014 and 1.5 times from 2015. Whether cylinder 8 lies on bank 1 or bank 2 depends on the maker's numbering, which tells you whether P219A or P219B should accompany it. As Toyota and Lexus bulletins on cylinder codes show, leaking or restricted injectors, an intake leak at one runner and leaking valves are the usual causes. An injector balance test and a leak-down test on cylinder 8 come before any sensor work.
P21A3 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 8 hours
- Clears after repairAfter a drive cycle
Symptoms of P21A3
- Check engine light on
- Usually no driveability change
- Possible P0308 with a strong deviation
Common causes of P21A3
- Most likelyCylinder 8 injector out of tolerance
- PossibleValve leakage at cylinder 8
- PossibleIntake leak at the cylinder 8 runner
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injector
What each part of P21A3 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 1 | Area: fuel and air metering. |
| A3 | The exact fault in that area. |
What to do next
- Note P21A3 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P21A3
What does P21A3 mean?
P21A3 means "Cylinder 8 Air-Fuel Ratio Imbalance". P21A3 blames cylinder 8, on a V8 the last cylinder in the numbering. It is a generic code, so it means the same on every make.
Is it safe to drive with P21A3?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P21A3 fail an emissions test?
Yes, it can. P21A3 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P21A3 to fix?
Difficulty: medium. A typical repair takes 0.5 to 8 hours of work. This is a job for a workshop.
Will P21A3 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.