Mass Air Flow (MAF) Sensor Intermittent The MAF sensor circuit is monitored by the PCM for sudden voltage (or air flow) input change through the comprehensive component monitor (CCM). If during the last 40 warm-up cycles in key ON engine running the PCM detects a voltage (or air flow) change beyond the minimum or maximum calibrated limit, a continuous memory diagnostic trouble code (DTC) is stored.
Some systems require that the actuator has an adequate supply of brake fluid. Low brake fluid levels can mimic the symptoms of code P1991, so consult the manual to locate the brake fluid reservoir. Bear in mind that a low fluid level can set code P1991 on some applications, so make sure that on fluid operated systems the fluid level is up to the mark before starting an electrical diagnosis.
When you turn on the ignition, the Service Engine Soon or Check Engine P1991 light should flash briefly, indicating that the OBD system is ready to scan your vehicle for any malfunctions. After this brief flash, the light should stay off while you drive as long as no problems are detected. If secondary air injection system switching valve a circuit malfunction so, you'll be glad to know that your vehicle is equipped with an early warning system that could save you time, money, and fuel in addition to helping protect the secondary air injection system switching valve a circuit malfunction.
Difficulty Level (Soso)
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Repair Time (50 Min.)
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| Cost Prediction : $ 30-110 |
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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.
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