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Hi Im David sorry you found a mechanic that apparently just like to throw parts at vehicles. let me see how i can help you. please allow me some time to pull up a little info...thanks
P0193 - Fuel Rail Pressure Sensor Circuit High Input
Possible causes - Low or no fuel - Faulty Fuel Rail Pressure Sensor - Fuel Rail Pressure Sensor harness is open or shorted - Fuel Rail Pressure Sensor circuit poor electrical connection - Faulty Fuel Pump
The Fuel Rail Pressure (FRP) sensor is a diaphragm strain gauge device in which resistance changes with pressure. The electrical resistance of a strain gauge increases as pressure increases, and the resistance decreases as the pressure decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signal to the Powertrain Control Module (PCM) corresponding to pressure. Strain gauge type sensors are consider passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow. Voltage that is dropped across a fixed resistor in series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor. The FRP sensor measures the pressure of the fuel near the fuel injectors. This signal is used by the PCM to adjust the fuel injector pulse width and meter fuel to each combustion cylinder.
P0101 VOLVO - Mass or Volume Air Flow Circuit Range/Performance Problem
The Mass Air Flow (MAF) sensor is placed in the stream of intake air. It measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is supplied with electric current from the Engine Control Module (ECM). The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to maintain the temperature of the hot film as air flow increases. The ECM detects the air flow by means of this current change.P0171 - System Too Lean Bank 1
Possible causes - Intake air leaks - Faulty front heated oxygen sensor - Ignition misfiring - Faulty fuel injectors - Exhaust gas leaks - Incorrect fuel pressure - Lack of fuel - Faulty Mass Air Flow (MAF) sensor - Incorrect Positive Crankcase Ventilation (PCV) hose connection
it is my opinion that the proper troubleshooting was not done. first they need to do a fuel pressure test. then then need to check the wiring between the fuel pressure sensor and the fuel pump. i believe the p0193 and p0171 are caused by the fuel pressure issue. the p0101 need to be troubleshot by testing the mass air flow sensor inputs and outputs.
if its intermittent like that i would definitely check the wiring.
hows it going?