Air Assisted Injector Control Circuit Low
What it means
P0066 means the control circuit for the air-assisted injection system is reading low — typically a short to ground or an open in the wiring, or a failed control valve. This system meters a small amount of air to the injectors to improve fuel atomization and lower emissions, mostly at idle and when cold. The engine usually still runs, but you may feel rough idle or weaker throttle response until the circuit is repaired.
Can I keep driving? Usually still drivable, but you may notice rough idle or weaker throttle response, especially when cold; get it looked at before it worsens.
Common symptoms
What you'll notice
- Check-engine light on
- Rough idle, especially when the engine is cold
- Reduced performance or hesitation
- Increased emissions
Common causes
Most likely first
- Faulty air-assisted injector control solenoid/valveLikely
- Short-to-ground or open in the control circuit wiring (reads low)Common
- Obstruction or contamination in the air-assist passageCommon
- Loose or corroded connectorLess often
- Failed ECM (rare)Less often
How to diagnose & fix
Work through it in order
- Confirm the code and inspect the air-assist control valve connector and wiring for shorts or opens.
- Check the air-assist passages for clogging or contamination.
- Test the solenoid/valve resistance against spec.
- Repair wiring or replace the control valve as needed.
- Clear and retest; replace the ECM only if everything else checks out.
FAQ
Quick answers
Is it safe to drive with P0066?+
Can I just clear P0066?+
Related codes
Often seen with P0066
Read & clear P0066 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.