P21BACold Start Cylinder 5 Injection Timing
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Check engine light after cold starts
- Rough idle during the first seconds after a cold start, possibly together with P050D
- Likely causes
- 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
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.