Primarily used to monitor intake air pressure, MAP sensors also help determine correct air-to-fuel ratio in vehicles without air mass sensors. The engine’s ECU will do this by using the air temperature and pressure to determine air density. In some instances, MAP sensors are even used to measure EGR valve performance in turbo applications (boost pressure sensors) to monitor the turbo output pressure.
As MAP sensors provide intake manifold pressure for the engine, fault codes (P0105-P0109) associated with them should be thoroughly checked to ensure that the cause of the fault is found.
Troubleshooting MAP sensor problems
Common symptoms that indicate a struggling MAP sensor include:
- Irregular engine RPM as a result of incorrect readings
- Turbo failure
- Loss of power
- Jerky acceleration
- Illumination of ‘check engine’ light
Some possible causes for MAP sensor failure
- Circuit broken between sensor and ECU
- Damaged wire connector
- Incorrect or worn air filter
- Leakages in vacuum system (i.e. vacuum-operated actuators, brake boosters, lines, etc.)
- Defective EGR valves that are perpetually open
Finding the cause of the problem
A vacuum leak can affect readings taken by a MAP sensor. Thus, a MAP sensor must be sealed in order to function properly. To ensure that there are no leaks, technicians should always check the sensor’s gasket and hoses from the intake manifold. If they are in working order, the sensor should be checked from the readings to gauge the air pressure the engine is receiving. If there are no problems with the pressure, the sensor should be checked if it is receiving voltage with a multimeter.
The sensor can also be tested by connecting a hand-held vacuum pump to the port of the sensor and a multimeter to the sensor’s connector. In normal conditions, the sensor should register between 1 and 2 volts at idle (this is where the sensor experiences high vacuum), and around 5 volts with the engine off but the ignition turned on*. If similar readings are not measured during the test with the vacuum pump, then the sensor is most likely to be faulty.
It is important that the test is not performed at a vacuum pressure above 20 inHg as this can damage the sensor.
(*always refer to the vehicle manufacturer’s data for accurate readings)
Cambiare’s MAP sensor range
Cambiare currently has more than 160 MAP sensors covering a total car parc of 31.3 million cars across the UK.
- VE372036, for Volkswagen Golf 1.6 (2009-2012)
- VE372076, for Volkswagen Golf Plus 1.9 (2005-2009)
- VE372147, for Vauxhall Astra Van 1.7 (2003-2005)
Backed by a 2-year/30,000-mile warranty, Cambiare parts are fully catalogued on the Cambiare website (www.cambiare-ve.com), the F:Drive and MAM Autocat. For more information, please speak with your local FPS representative.