Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

MAP sensor and fuel economy


I was just told by the mechanic who just did a OBD scan that the MAP sensor on my 2001 Hyundai Elantra Automatic is faulty. I’m not sure how long this have been happening since i’ve not had the car scanned (at least not that I am aware. Do cars normally get an OBD scanned during general maintenance/ tune up by a non-dealer mech??)

Anyway my question is that is there a link between a faulty MAP sensor with fuel economy of a car? since I think that the fuel economy for the car is bad or could be better.


A faulty MAP sensor can degrade performance also along with other sensors. Also make sure the coolant temperature sensor is working like it should. The mechanic can watch the action with his scanner.

OK…maybe a bad question to ask in the first place. maybe the best way is to ask the following:

do sensors (in general) go bad just like a flick of a switch or it gradually go from good to bad.

I assume that if it is a gradual process then the effect on car performance is also gradual.

Sensors are electrical components and that means they can work on minute and fail the next, just like a light bulb. Some sensors are in places that get dirty and over time they degrade gradually. So, you have both instant failure and slow gradual failure depending on the sensor and what it is measuring.

Thanks for the reply.

so for the MAP sensor…which type of failure is it?

MAP sensor is often a “wire” that reads the air passing by it. Sometimes the wire breaks, sometimes the electrical part fails, and sometimes the wire is just dirty and can be cleaned.

If yours is dirty it degraded over time to a point where it isn’t giving dependable information anymore and caused the code on the computer. I doubt it will be a miracle rebound in fuel economy when it is repaired. It may make a positive difference, but don’t expect too much. A dirty air cleaner, old spark plugs, and other items may need to be maintained to bring back top fuel efficiency.

“which type of failure is it?”

Your mechanic with a meter and service manual specs should be able to measure the sensors’ resistance and tell. He can tell if it’s dirty by visual inspection.

Actually, isn’t a MAP sensor more of a diaphragm and a calibrated spring, connected to a potentiometer? A MAF sensor would be the wire type that senses the air density. Engines usually have one or the other, depending on the management system designer’s preference. If I’m wrong, bring on the flames :slight_smile:

Sensors can also fail in such a way that they are just slightly out of range, or performing just under spec. Enough to degrade driveability and performance, but not enough to cause the computer to set a code. Maddening to troubleshoot one of these.