P21E4 code meaning
Cylinder 5 Injector B Circuit Low
Powertrain system Generic code P21xx codes Check engine light
What P21E4 means
P21E4 flags a low state on the circuit of the second (B) injector serving cylinder 5. The only public OBD summary that lists it is GM's for the 2019 Corvette ZR1, whose supercharged LT5 V8 pairs direct injectors with port injectors and drives the supplemental ones from a separate fuel injection control module (FICM). While that driver is off, a low side reading 0.5 Ohm or less toward ground in 20 of 25 samples, taken every 100 ms, is judged a short and becomes a Type A fault with the MIL in the first trip. On GM's V8 numbering cylinder 5 is the third cylinder of the left bank, i.e. bank 1. Because a grounded low side can let the injector flow uncommanded, a rich bank 1 may follow. Ford's dual-injection engines report B shorts on this cylinder only as P21D3.
P21E4 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyHard
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P21E4
- Check engine light on
- Rich running or fuel trim pulled back on bank 1
- Rough idle or misfire on cylinder 5
Common causes of P21E4
- Most likelyLow-side wire of the cylinder 5 B injector touching ground
- PossibleInjector winding shorted to its housing
- PossibleMoisture or corrosion in the injector connector
- Less likelyDriver stage in the injection control module faulty
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 P21E4 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. |
| E4 | The exact fault in that area. |
What to do next
- Note P21E4 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 P21E4
What does P21E4 mean?
P21E4 means "Cylinder 5 Injector B Circuit Low". P21E4 flags a low state on the circuit of the second (B) injector serving cylinder 5. It is a generic code, so it means the same on every make.
Is it safe to drive with P21E4?
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 P21E4 fail an emissions test?
Yes, it can. P21E4 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 P21E4 to fix?
Difficulty: hard. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will P21E4 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.