What it means
The control module detected a high electrical signal in the cylinder 3 injector B circuit. This indicates an electrical circuit condition; it does not by itself establish injector flow or cylinder fuel balance.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Injector B is the second injector circuit identified for cylinder 3 by the control system; P21E1 flags its electrical signal rather than confirming an injector-flow imbalance. The control module sets this code when the signal is higher than expected, which can point to a short to voltage, connector trouble, or an injector electrical fault.
Common causes
Most likely first.
- Short to voltage in wiring
- Damaged or corroded connector
- Injector electrical fault
Symptoms
- Check-engine light on
- Rough running or misfire
- Reduced engine power
- Increased fuel consumption
How to diagnose it
- Record freeze-frame data and scan for cylinder 3 misfire and related injector codes to determine the conditions when the high signal was detected.
- Inspect the cylinder 3 injector B wiring and connector for exposed conductors, corrosion, loose pins, or contact with a powered circuit.
- Use the vehicle wiring information to locate the circuit and check for a short to voltage with the circuit isolated as directed by the manufacturer.
- Check terminal fit and circuit continuity with injector B disconnected according to the manufacturer’s procedure.
- Test the cylinder 3 injector B electrical characteristics against the manufacturer’s specification.
Common fixes
- Secure the cylinder 3 injector B connector and clean or replace corroded terminals.
- Repair damaged insulation or wiring that is shorting the circuit to voltage.
- Replace a connector or terminal that is damaged and cannot make a reliable connection.
- Replace injector B for cylinder 3 if it fails the manufacturer’s electrical test.
Can I keep driving?
Limit driving if the engine is misfiring or losing power; continued misfire can raise emissions and overheat the catalytic converter. Stop if the engine runs severely unevenly or the warning light flashes.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.