U2638 Diagnostic Trouble Code

U2638 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 U2638 diagnostic trouble code may include:

Fuel pressure too low
Rich or lean exhaust
Diminished fuel efficiency
The engine oil will exhibit dilution from the ECUs attempts to increase engine temperature. Some vehicles advance the fuel injection timing slightly after top center to afterburn a small amount of fuel to increase exhaust temperatures. Some of this fuel enters the crankcase. When the ECU determines the necessity to regenerate the DPF, the service life of the oil be shortened significantly

Possible Causes :

Defective ECU strategies or components will prevent proper regeneration
The Mass Airflow sensor is a hot wire that senses the volume of air entering the intake manifold. The computer uses this information to control fuel mixture.
Faulty IMRC actuator/sensor

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. It should be pretty close to battery voltage (12 volts). If not, then this is the circuit that has the problem.

Process Tips

Diagnostic trouble code U2638 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 U2638.

Fortunately, U2638 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U2638 Trouble Code For Specific Cars

U2638 Dutton B-plus IMRC Input Error (Bank 2)
U2638 Trabant 601 Passenger Sid, Side mount Airbag Circuit Short to Ground
U2638 Austin Montego Aux A/C Blower Speed 1 Circuit Short to Ground
U2638 Kia Amanti Seat Rear Up/Down Potentiometer Feedback Circuit Open
U2638 Vauxhall Astra Power Window RR Motor Circuit Short To Ground
U2638 Ford Probe Gt Mirror Passenger Horizontal Feedback Potentiometer Circuit Short to Ground
U2638 Skoda Scala Lack Of HO2S Switch - Sensor Indicates Rich