U0127 Diagnostic Trouble Code

U0127 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 U0127 diagnostic trouble code may include:

Lack of power
Faulty O2 Sensor
Poor acceleration
Engine surge

Possible Causes :

Rarely - faulty Powertrain Control Module (PCM-programming required after replacement)
Rough running engine due to misfiring plugs. Many engines have misfire codes to indicate the cylinder effected, such as P0307 for number 7.
A large vacuum leak would cause a massive amount of un-metered air to enter the intake manifold resulting in an overly 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. Check to make sure they are not burnt or corroded. If in doubt, get some Electrical Contact cleaner at any parts store if cleaning of the terminals is needed. Replace the oxygen sensor that is downstream from the catalytic converter on the side of the engine that does not contain cylinder #1. Also, if a oxygen sensor code stating "heater circuit malfunction" the sensor has most probably failed.

Process Tips

Diagnostic trouble code U0127 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 U0127.

Fortunately, U0127 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U0127 Trouble Code For Specific Cars

U0127 Toyota Mr2 Output Speed Sensor Circuit Malfunction
U0127 Mercedes-benz S Class Air Suspension Front Height Sensor High (SE) Signal Circuit Short To Ground
U0127 Plymouth Trail Duster Exhaust Gas Recirculation Circuit Range/Performance
U0127 Mcc Forfour A/C Pressure Sensor Insufficient Pressure Change
U0127 Paykan High Line Driver Window Up / Down Power Circuit Short to Ground
U0127 Kia Avella Seat Rear Up/Down Potentiometer Feedback Circuit Short To Battery
U0127 Mazda Mazda 6 Ii Turbocharger Boost Sensor A Circuit Low