U3999 Trouble Code

View U3999 obd/2 error code description and symptoms. U3999 engine photo

Output Shaft Speed sensor circuit intermittent failure The output shaft speed sensor signal to the PCM is irregular or interrupted.
Harness connector not properly seated Harness intermittently shorted, or open Harness connector damaged OSS sensor damaged, or not installed properly Verify harness and connector integrity Verify OSS sensor proper installation.

As the engine heats up and combustion becomes easier and more complete, the PCM will command the idling control valve to increase the amount of air entering the engine to suit the changing conditions. However, when the load on the engine changes, say, when some electrical consumers or other systems are either turned on or off, the PCM adapts the signal voltage to the idle control valve to ensure that the idling speed remains stable, and at the RPM specified by the manufacturer.

U3999 Error Code Repair Process :

OBD U3999 code and tailpipe testing are two different approaches to identify vehicles in need of repair. The OBD system looks for broken or malfunctioning emissions control components and servo motor vent circuit failure, while tailpipe tests sample a vehicle's exhaust to see if it is above or below certain prescribed limits. Given the robust nature of today's emissions control components, it is entirely possible for an individual component to U3999 malfunction without leading to an immediate increase in emissions at the tailpipe. In such cases, other components (like the catalyst) can temporarily compensate for the part that is broken however, these other components can only do double duty for so long before they, too, begin to malfunction. In addition, OBD also monitors for U3999 and other malfunctions in the fuel system problems that traditional tailpipe tests were not designed to identify. Most state and local areas also include a gas cap pressure test as part of an emission inspection.

U3999 is a kind of Network Trouble Code

U-code indicates that engine communication errors and shows lost communication with engine parts.U-Codes are fairly straight forward, given all of the articles and technical publications that have been written regarding these problematic codes. In most cases, it just comes down to identifying the module that isn't communicating with the other modules on the CAN bus line for whatever reason.

Common Causes of U3999

A common cause of code U3999 is the failure of Servo Motor Vent Circuit Failure, but there are several other possible causes as well, such as ;

Camshaft Position Sensor harness is open or shorted
Faulty select solenoid
Ignition coils harness is open or shorted
Exhaust gas leaks

U3999 code for all cars

You can view according U3999 DTC for your car model. We selected several models to see obd2 solutions click and view it.

+U3999 Mercedes Clk 200

Engine OBD 2 Codes website is a freeware resource center for engine trouble codes.

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