The Barometric Pressure Sensor (BPS), located in the volume air flow sensor assembly, converts the barometric pressure into voltage, and then inputs that voltage (as signals) to the ECM. The ECM, based upon those signals, then corrects the amount of fuel injection, etc.
If there is a malfunction of the BPS, driveability of the vehicle will become worse particularly at higher altitudes. When it appears as though the BPS is malfunctioning, first check the air cleaner for a clog or restriction. A restriction of the air cleaner sometimes causes a reactions as though the BPS were malfunctioning.
See Figure 1
The 1993-95, rear-wheel drive 2.4L (California) Pick-ups have the same engine controls as the 3.0L engines. All other 2.4L engines are listed as 2.4L engines.
- Since the BPS is located in the volume air flow sensor box, the harness connector (HC) to this box will be the wiring tested throughout this procedure. Unplug the volume air flow sensor HC from the volume air flow sensor assembly box.
- Check terminal 5 of the HC for continuity to ground. If there is no continuity in the circuit, repair or replace the harness between terminal 5 of the HC to terminals 14 and 24 of the ECM.
- Turn the ignition switch to ON and measure the power supply voltage of terminal 1 of the HC. If the voltage is not between 4.8-5.2 volts, repair or replace the harness between terminal 1 (HC) and terminals 13 and 23 (ECM).
- Turn the ignition switch OFF and unplug the ECM harness connector. Check for an open or short-circuit to ground, between terminal 16 (ECM) and terminal 2 (HC) for 2.4L and 3.0L (12 valve) engines, terminal 61 (ECM) and terminal 2 (HC) for 3.0L (24 valve) and 3.5L engines. For all engines except for the 2.4L, check also terminal 23 (ECM) and terminal 1 (HC) for 3.0L (12 valve) engines, terminal 65 (ECM) and terminal 1 (HC) for 3.0L (24 valve) and 3.5L engines. If there is a short or open-circuit, repair or replace the harness between these terminals, otherwise the harness is good.
To correctly test this component a Mitsubishi MUT or MUT II tool is needed. Mitsubishi does not give testing procedures of the volume air flow sensor itself with an ohmmeter. Due to the high cost, and special skills needed to operate the tool, have the system diagnosed by a dealer or reputable service facility.
REMOVAL & INSTALLATION
Since the BPS sensor is integral to the volume air flow sensor assembly, refer to the previously described removal and installation procedures for the volume air flow sensor.