U0138 Diagnostic Trouble Code

U0138 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 U0138 diagnostic trouble code may include:

Blown fuse (if applicable)
Engine surge
Reduction in engine performance, especially at low RPM levels
The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.

Possible Causes :

An air leak forward of the DPF will change the sensor readings resulting in the code
Rusty exhaust systems, cracked exhaust manifolds or damaged or missing gaskets or donuts will cause air leaks.
Dirty air cleaner element Damaged DPF

Repair Processes :

It should be pretty close to battery voltage (12 volts). If not, then this is the circuit that has the problem. 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. If the engine displays a miss and there wasn't a code, determine which cylinder is misfiring. If the exhaust manifold is visible, spay or pour a small amount of water on each cylinder exhaust port. Water will evaporate immediately on good cylinders and slowly on the missing cylinder. If this can't be accomplished pull the plugs and check the condition.

Process Tips

Diagnostic trouble code U0138 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 U0138.

Fortunately, U0138 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

U0138 Trouble Code For Specific Cars

U0138 Great Wall Steed 5 Passenger Seat Occupant Detection Circuit Short To Battery
U0138 Mercedes B 160 ABS Hydraulic Pressure Differential Switch Input Open Circuit
U0138 Lancia Stratos Stability Control Inhibit Warning
U0138 Ginetta G34 Output Circuit Check Signal High
U0138 Itala Racecar SCP (J1850) Invalid or Missing Data for Vehicle Speed Control
U0138 Pontiac 1000 Exhaust Gas Recirculation Sensor B Circuit High
U0138 Lincoln Mark Lt Throttle position sensor intermittent