How To Troubleshoot A Vehicle MAP Sensor

9 November 2017
 Categories: , Blog

If you suddenly experience poor gas mileage, hesitation, or rough idle, the MAP sensor in your vehicle could be faulty. A MAP sensor (manifold absolute pressure installed in fuel injector systems that measures the absolute pressure from the engine intake manifold.

It sends a signal to the electrical panel to increase or reduce fuel. Before you see a mechanic, try these troubleshooting tips.

Inspect  the MAP Pump

Shut off the engine and let it cool. The MAP pump is commonly located near the motor compartment or firewall on the passenger side. The MAP uses the pump to make pressure calculations, so any obstructions or damage could hinder it. Check wires for damage, and make certain they are secured.

Connect the Voltmeter or Tachometer and Pump

Detach the pump, and test the pump with a manual hand vacuum system and voltmeter for vehicles that operate on current or tachometer (a device that measures engine speed) for vehicles that operate on frequency. 

A hand vacuum pump can commonly be rented from automotive stores. Refer to your manual to determine the type of sensor.

Connect the hand pump to the nipple on the MAP sensor, and switch the ignition on, but don't start the vehicle. Detach the MAP electrical connector, and turn the key, but don't start the motor. 

For volt type sensors, set the voltmeter to DC, attach the positive volt meter lead to the reference wire, consulting your manual for identification. Connect the negative lead of the voltmeter or tachometer to the black ground wire, located on the end of the connector. 

Apply Pressure

Refer to your vehicle's manual for wiring diagrams and suggested voltage. Check the reading without pressure., which should be between 3 volts and 5 volts, or between 300 and 320 RPM( Rotations Per Minute) Pump 5Hg of pressure which should give a 3.5 reading or Pump 20Hg, which should give around a 1.1-volt reading. 

If the reading is good, but the check engine light still shows, inspect the O-rings for damage. It could also mean the locking tab has broken on the sensor causing a loose wire connection or a faulty fuel pump.

Check voltage from wires coming from the computer. If voltage remains low at the sensor, but it gives the suggested voltage at the computer, it can usually be traced to the reference wires. 

Test the voltage of the reference wire. A reference wire should produce 5 volts only. If it shows a low voltage at the computer, and the reference wire shows 5 volts, inspect the wires for damage.