The issue covered by the bulletin involves a power steering noise/whine or fluid leak from the power steering pump, gear or high pressure side power steering hose during extreme low outdoor temperature operation.
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.
OBD P1991 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 secondary air injection system switching valve a circuit malfunction, 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 P1991 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 P1991 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.
Difficulty Level (Soso)
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Repair Time (30 Min.)
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| Cost Prediction : $ 40-60 |
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P1991 is a kind of Powertrain Trouble Code
Powertrain of a modern automobile, comprising engine (with exhaust system), transmission, drive shaft, suspension and the wheels. In a motor vehicle, the term powertrain or powerplant describes the main components that generate power and deliver it to the road surface, water, or air. |
You can view according P1991 DTC for your car model. We selected several models to see obd2 solutions click and view it.
Engine OBD 2 Codes website is a freeware resource center for engine trouble codes.
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