U1177 BMW Fault Code

Description:

The input turbine speed sensor detects rotation of the input shaft of the input shaft speed sensor transmission. The computer uses that information, along with the output shaft speed sensor to determine if the transmission is operating according to plan. If the computer detects a difference between the input shaft speed , and the expected output shaft speed, it will adjust transmission pump pressure to prevent clutch disc slip. If adding pressure doesn't solve the problem, it will set a trouble code.

U1177 Code Symptoms :

OBD U1177 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 U1177, 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 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 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.

Diagnosis And Repairing U1177

U1177 OBD2 reports a sensor fault, replacement of the sensor is unlikely to resolve the underlying problem. The fault is most likely to be caused by the systems that the sensor is monitoring, but might even be caused by the wiring to the sensor itself.

How to fix U1177 code ?

• Damaged VCT phaser
• Damaged camshaft position (CMP) sensor
• Continuous oil flow to the VCT piston chamber
• Faulty Air fuel ratio (A/F) Sensor 1 Bank 1

As long as the throttle plate remains closed, the idling speed and quality is controlled by the PCM via the idle control valve, and as can be seen from the above it should be clear that idle control on a gasoline engine is a complex affair.

For instance, if the engine is started in sub-zero temperatures, the PCM will command the idling control valve to allow less air to enter the engine to enrich the air/fuel mixture to create a condition which is roughly analogous to how chokes worked on carburetted engines to control idling in cold weather.