P21BA code meaning
Cold Start Cylinder 5 Injection Timing
Powertrain system Generic code P21xx codes Check engine light
What P21BA means
P21BA can only occur on engines with at least five cylinders – inline fives, V6, V8 and larger. GM's 4.3-litre V6 and 5.3/6.2-litre V8 direct-injection engines use a dual-pulse injection in open loop after a cold start; a GM bulletin explains that the module watches crankshaft speed in this mode and sets P050D (cold start rough idle) if it varies too much. A per-cylinder timing code such as P21BA goes a step further and names the cylinder whose cold-start injection timing missed its target. No manufacturer has published use of P21BA. On which bank cylinder 5 sits depends on the manufacturer's numbering, so check the engine's cylinder layout before testing. Related: P020E (warm), P2B0C (cold-start pulse), P0305.
P21BA at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyHard
- Typical labor0.7 to 4 hours
- Clears after repairAfter a drive cycle
Symptoms of P21BA
- Check engine light after cold starts
- Rough idle during the first seconds after a cold start, possibly together with P050D
Common causes of P21BA
- Most likelyInjector of cylinder 5 sticking or delivering late when cold
- PossibleRepair on the wrong injector because of a misread cylinder numbering
- PossibleOpen or high-resistance circuit to injector 5
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injectorInjector wiringEngine control module
What each part of P21BA 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. |
| BA | The exact fault in that area. |
What to do next
- Note P21BA 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 P21BA
What does P21BA mean?
P21BA means "Cold Start Cylinder 5 Injection Timing". P21BA can only occur on engines with at least five cylinders – inline fives, V6, V8 and larger. It is a generic code, so it means the same on every make.
Is it safe to drive with P21BA?
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 P21BA fail an emissions test?
Yes, it can. P21BA 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 P21BA to fix?
Difficulty: hard. A typical repair takes 0.7 to 4 hours of work. This is a job for a workshop.
Will P21BA 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.