What does code P0066 mean?
The P0066 fault code, applicable to all car manufacturers, means “Air Assisted Injector Control Circuit or Circuit Low“.
Background information: Air-assisted injectors optimize fuel combustion by introducing high-pressure air into the fuel injection channel to create a finer fuel mist. This fault code appears if the electronic control unit (ECU) detects that the voltage in the air-assisted injector control circuit is below the calibrated minimum value. Possible causes include a faulty air-assisted injector solenoid valve itself or its circuitry, a faulty oxygen sensor, or a faulty powertrain control module (PCM).
Symptoms of Error Code P0066
- When error code P0066 appears, the driver may notice the following signs:
- Unstable idling
- Engine “triple” or intermittent operation
- Increased fuel consumption
- Loss of power during acceleration
- Delayed throttle pedal response
- The engine check light illuminates
Main Causes of Error Code P0066
- Air control valve malfunction
- Damaged or broken control circuit wiring
- Ground or power supply failure in the circuit
- Damaged or oxidized valve connectors
- Engine control unit (ECU) malfunction
How to Diagnose Error Code P0066?
- Connect an OBD2 scanner and read the fault codes. Record all current and saved errors.
- Clear the error codes and start the engine. Check if the P0066 code reappears.
- Visually inspect the electrical wiring and valve connectors. Check for integrity, damage, and corrosion.
- Connect the circuit from the ECU to the valve. Check the valve resistance (typically between 20-40 ohms, but varies by model).
- Check the valve operation with battery power (disconnect the connector).
Possible Causes and Diagnostic Methods
| Possible Causes | How to Check？ |
|---|---|
| Air control valve defect | Check resistance, try feeding |
| Open wire or short circuit | Perform visual inspection, around the circuit |
| Console damage or contact oxidation | Clean connector, apply dielectric grease |
| Engine control unit problem | Parameter scan, output verification |
Required tools: OBD-II diagnostic scanner, multimeter, valve access kit, dielectric grease, power cord (test kit)
How to resolve error code P0066? (Solutions to the Problem)
Simple Repair Methods
- Clean the valve connector and apply protective lubricant.
- Reset the error and recheck (if the error is accidental).
- Replace the fuse if there is a protected circuit.
In-depth Diagnostic and Repair Solutions
- Replace the faulty air control valve.
- Repair or replace damaged wiring.
- Inspect and repair the control unit output circuit.
- ECU replacement (in rare cases).
Troubleshooting Through Symptoms
| Symptoms | Possible Solutions |
|---|---|
| Unstable idling | Inspect and replace valves, restore wiring |
| Increased fuel consumption | Diagnose valves and control circuits |
| Power outage | ECU output test, may need to replace valves |
| Delayed gas response | Clean contacts, replace defective components |
Error Code P0066 in Different Vehicles
P0066 in Mazda: In Mazda vehicles equipped with SkyActiv engines, error P0066 may occur due to a clogged metering valve or an electric drive malfunction. Valve replacement is usually required.
Ford P0066: In Ford models (Focus, Mondeo) equipped with Duratec engines, the error is caused by connector contact corrosion or a short circuit. It is recommended to check the integrity of the wiring harness.
Mercedes-Benz P0066: In the OM642 diesel engine, error P0066 typically indicates an intake manifold actuator failure. Mechanical and electrical systems must be checked.
Volkswagen P0066: Volkswagen vehicles equipped with TSI engines may experience this error due to a secondary air supply valve failure. Valve and circuit diagnostics are mandatory.
BMW P0066: In BMW N-series motors, the P0066 error may be caused by a fault in the actuator’s electrical components. Diagnosis is performed using proprietary software.
P0066 Frequently Asked Questions
Is it possible to drive with a P0066 error?
It is not recommended, as a faulty air supply valve can lead to engine instability, increased fuel consumption, and degraded environmental performance.
Does error P0066 affect fuel consumption?
Yes, an air supply system malfunction can disrupt the fuel-air mixture, leading to increased fuel consumption.
Can I fix error P0066 myself?
Yes, with basic skills and tools, you can inspect connectors, clean contacts, or replace valves. However, for complex diagnostics, it’s best to contact a service provider.
How quickly can I fix a P0066 error?
Simple causes can be resolved within 30 to 60 minutes. More complex cases, such as replacing wiring or ECU diagnostics, may take several hours.
Could error P0066 be accidental?
Sometimes. The error may occur due to temporary contact failure or moisture. However, if it recurs, diagnostics are necessary.
Related OBD2 Errors for P0066
P0065 – Air Assisted Injector Control Range/Performance
P0067 – Air Assisted Injector Control Circuit High
P0070 – Ambient Air Temperature Sensor Circuit
Important! In some cases, the vehicle may function normally, but the error may occur periodically. However, ignoring this issue can lead to decreased engine performance and increased emissions. Regularly inspect the wiring under the hood. Preventative cleaning of connectors and moisture protection can significantly reduce the likelihood of such errors occurring.