U0266 Diagnostic Trouble Code

U0266 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code.

It is considered generic because it applies to all makes and models of vehicles, although specific repair steps may be different depending on your car model.

Symptoms

Symptoms of a U0266 diagnostic trouble code may include:

Poor acceleration
Cherry red hot catalytic converter
Possible spark knock (detonation / pre-ignition)
Reduction in engine performance, especially at low RPM levels

Possible Causes :

A faulty oxygen sensor. This will set a code in itself, however, a faulty oxygen sensor does not automatically condemn the sensor. The code just means that the sensor signal was not within specifications. An air leak or any of the above will cause an erroneous signal. There is a multitude of O2 codes relating to O2 performance which gives a clue to the problematic area.
Some aftermarket accessories and performance modifications
A large air leak at or near the number one oxygen sensor would also cause a lean mixture.

Repair Processes :

With the valve disconnected, the red voltmeter lead should be attached to the IMRC valve power wire and the black voltmeter lead connected to ground. Look for rubbing, scraping, bare wires, worn spots or melted plastic connectors. Pull the connectors apart and carefully look at the terminals (the metal parts) inside the connectors.

Process Tips

Diagnostic trouble code U0266 is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.

Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before U0266.

Fortunately, U0266 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U0266 Trouble Code For Specific Cars

U0266 Oldsmobile 88 Cylinder 5 Injector Circuit Low
U0266 Renault Grand Scenic Glow Plug Circuit Low Input (Bank #1)
U0266 Fiat Campagnola Lamp Headlamp Low-Beam Circuit Short To Battery
U0266 Aston Martin Db4 Air Suspension RR Air Spring/Shock Solenoid Output Circuit Short To Battery
U0266 Gobron 18 Park/Neutral Switch Circuit Open
U0266 Renault Dauphine Gear Shift Position Circuit Low
U0266 Audi A1 Ambient Air Temperature Sensor Circuit Intermittent