P0066: Air Assisted Injector Control Circuit or Circuit Low
What to do
Usually driveable with poorer cold running.
What this code means
An electrical fault in the air-assisted injection control circuit, reading low or open. Because the hardware is uncommon, parts availability is often the practical constraint rather than the diagnosis itself — confirm the fault properly before ordering anything.
Likely causes
Start here
- Wiring shorted to ground · moderate
- Failed air assist control valve · moderate
- Corroded or loose connector · easy
Less common
- Open circuit in solenoid wiring · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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