A series of sensors control electrical systems in modern cars. These sensors carry out different functions to bring out the proper functioning of the vehicle.
The MAP sensor of my car stopped working correctly some time ago. I instantly knew that something was wrong with my car. Though the car was generally running fine, the engine would occasionally stall. After some investigation, it became clear that the MAP sensors were damaged. If any of these sensors malfunction, it’s as if the senses of the car have reduced.
This article will shed light on bad MAP sensor symptoms and their functions.
Table of Contents
What is a MAP Sensor?
Manifold absolute pressure sensor, otherwise known as the MAP sensor, measures the pressure of air entering your car’s intake manifold. The reading of this total pressure is conveyed to the ECU.
According to this pressure, ECU calculates the amount of air entering the intake manifold. The fuel intake is then matched to keep the air-fuel ratio of the mixture entering the combustion chamber at optimum levels.
How Does a MAP Sensor Work?
Like any other sensor, the MAP sensor has a sensing and calibration unit. The sensing element is usually a bellow that expands as the air enters it. The expansion of this bellow is calibrated against a predetermined scale.
MAP sensors can measure pressure accurately within 1 bar. They’re actually calibrated to read intake pressure at 1 bar higher than the actual pressure. This feature ensures that the engine is always running lean.
Some vehicles employ a mass airflow sensor (MAF sensor) and the MAP sensor to measure pressure more accurately.
Another critical point is that MAP sensors can never read negative pressure. So anything below 1 bar will be considered a perfect vacuum by the sensor. Hence, the name absolute pressure sensor.
The MAP sensor is nothing but a mere pressure gauge. But instead of an analog output, it generates output in the form of an electrical signal, which is interpreted by the car’s engine control unit (ECU).
If the MAP sensor signals that more air is entering, the ECU commands the fuel injectors to inject more fuel, and vice versa.
Where is the MAP Sensor Located?
The MAP sensor is in the intake manifold of your car. It makes sense that the manifold absolute pressure sensor is located inside the intake manifold.
Why Does a MAP Sensor Go Bad?
The MAP sensor is an electromechanical component. Many things can go wrong with it. Most of the time, it just catches the dirt and debris from incoming air and cannot function properly.
Similarly, the bellows and small gears inside the sensor are subjected to wear. They can stop functioning after a length of time.
Symptoms of a Bad MAP Sensor
Following are the major symptoms of a failing map sensor:
- Check Engine Light
- Limp Mode
- Failure of Spark Plugs
- Poor Fuel Economy
- Unburnt Fuel in Exhaust
- Clogged Catalytic Converter
- Engine Knocking and Misfiring
- Stalling and Rough Idle
- Lack of Power
Let us take a close look at the signs of a faulty MAP sensor.
Check Engine Light
If the MAP sensor stops working, you’ll get a check engine light on your dashboard. The check engine light can mean many things, but most of the time, it is due to a failed sensor.
In case of a bad MAP sensor, the engine control module either reads air pressure too high or too low. In both cases, the balance of fuel injected by the fuel system is off. This excess or insufficient amount of fuel is considered an abnormality by the engine control module.
Hence, this is why you get a check engine light when the MAP sensor is malfunctioning.
A bad MAP sensor can put your car into limp mode. Limp mode limits the functionality of your vehicle. Particular frills and assistive functions will no longer be available and might disrupt your driving. For example, the top speed of your vehicle can be limited. You might not be able to surpass a specific speed, which is usually in the range of 40-50 mph.
Limp mode is a protective shield that comes on when something is wrong with your vehicle to prevent it from further damage.
Failure of Spark Plugs
A faulty MAP sensor can mean too much fuel being injected into the combustion chamber of your engine. No spark plugs are present in the CI (compression-ignition or diesel) engine, but in the SI engine (spark ignition or gasoline), spark plugs ignite the compressed air-fuel mixture at the end of the compression stroke.
Exposure to higher amounts of fuel can build carbon deposits on the tip of spark plugs causing them to fail sooner than expected. A spark plug should not fail before 20,000 to 30,000 miles. If your car’s spark plugs are going out before this, it might be due to a bad MAP sensor.
Poor Fuel Economy
A bad MAP sensor can also hurt the fuel economy of your car. If the intake manifold signals the engine control module that pressure is higher than usual, the ECU will increase fuel injection. More fuel injection will mean burning more fuel.
This change in fuel injection rate can significantly decrease your car’s fuel economy.
Unburnt Fuel in Exhaust
Too much fuel is not only bad for your engine, but it can also affect the functioning of the exhaust system in your car. The engine’s combustion cycle will consume only a set amount of fuel. If a faulty MAP sensor causes too much fuel to enter the combustion chamber, the excess fuel will remain unused.
This excess fuel will end up in the exhaust system and remain unburnt until the end. It can have severe implications for the environment since the fumes of unburnt fuel are highly hazardous to health.
Clogged Catalytic Converter
A bad MAP sensor can also clog the catalytic converter. The catalytic converter is present in most modern cars to break down harmful gases such as carbon monoxide, produced as combustion byproducts.
A faulty MAP sensor can bring in higher amounts of fuel. This excess fuel will go to waste, eventually getting trapped in the catalytic converter of your car. This buildup increases the chances that the filter of your catalytic converter will get clogged, and your car will be choked.
Engine Knocking and Misfiring
Engine knocking and misfiring is another situation that a bad MAP sensor can cause.
Knocking and misfiring are relatively similar concepts with a slight difference. During the compression stroke of the engine cycle, the air-fuel mixture is ignited at the end. This creates a shock wave, and from the side of the cylinder, the mixture burns till the other end.
If an adequate supply of fuel is not present, this sequential burning of the mixture is compromised. It generates air pockets and holes in the cylinder. These holes and pockets burst when fuel reached them, causing the engine to knock.
Similarly, if too much fuel is supplied in the combustion chamber, it will ignite before reaching the desired location. This is called misfiring.
Both misfiring and knocking are very harmful to the engine and can decrease its life considerably.
Stalling and Rough Idle
Where a bad MAP sensor can inject too much fuel into your engine, it can also limit its supply. When the amount of fuel is lower, the engine is said to be running on a “lean” air-fuel mixture.
Such a situation can cause your engine to stall. When at higher speeds, you’ll feel that the engine has lost power or is not generating enough power. The change you feel is due to the break in the power cycle. An inadequate supply of fuel causes this gap.
Rough idling is another scenario that drivers can anticipate if fuel intake fluctuates. When your engine is running idle, it might vibrate more than usual, and you’ll hear some odd engine noise.
Lack of Power
Fuel is the ultimate power producer in the engine of your car. If an adequate supply of fuel is missing, the engine will lag.
The amount of power available at the driveshaft is decreased, creating difficulty while accelerating. Upon pressing the gas pedal, you’ll feel like the car has become powerless. It will not respond in the way it should.
MAP Sensor Replacement Cost
The replacement of the MAP sensor can cost you somewhere between $110 and $240. You can see that it’s not that expensive, compared to some other repairs.
The sensor itself costs between $60 and $190, depending upon the make and model of your car. The labor cost can range between $50 and $90.
Almost all sensors are very inexpensive; the main reason for their replacement cost is that they’re deep inside the engine. Getting to them is a challenging task.
Luckily, In the case of a MAP sensor, the intake manifold is on the top of the engine. So, you can access it quite easily for replacement.
How To Replace a MAP Sensor?
Most of the time, you only need to clean the sensor. So, you can save the replacement cost. Accessing the MAP sensor is straightforward. By following these simple steps, you can replace the MAP sensor yourself:
- Locate the MAP sensor first. It must be present somewhere near the intake manifold of your engine.
- Once you have located the MAP sensor, disconnect the battery’s negative terminal.
- Now disconnect the vacuum hose attached to most MAP sensors.
- Check that the length of the new vacuum hose is the same as the old one. If not, trim it according to the required size.
- Detach the electrical wires that are attached to the MAP sensor. Tag each of these wires so that there is no confusion when you come back for installation.
- Remove the sensor. For this step, you might have to remove a few bolts.
- Remove the old sensor and place the new one in its spot.
- Tighten the bolts holding the sensor in place.
- Reconnect the vacuum hose.
- Attach the electrical connection wires as you tagged.
- With the help of an OBD2 scanner, you might have to reprogram the new MAP sensor.
- Now you can connect the negative terminal of the battery as well.
- See that the check engine light must have disappeared now.
Common MAP Sensor Fault Codes
If you see a check engine light, immediately scan your car for fault codes. In case if the MAP sensor has gone bad, you will receive the following codes:
P1106 – MAP sensor or BARO sensor is no longer functioning correctly. You will receive a hi/lo voltage signal.
P1107 – You will receive this code when the air-fuel mixture ratio is disturbed.
P0068 – If the throttle position sensor and MAP sensor readings are not coherent, you will receive this code.
P0069 – MAP atmospheric pressure measurement is out.
MAP (manifold absolute pressure) sensor is a critical a component of your vehicle. It upholds the integrity of your car’s engine.
Reporting wrong air pressure can bring in amounts of fuel that are incorrect for your vehicle’s air:fuel ratio.
Suppose excess fuel is injected into the combustion chamber. In that case, the fuel mileage is decreased, carbon deposits build in the exhaust system, components like spark plugs fail sooner, and the catalytic converter can get clogged.
Similarly, if insufficient fuel is supplied, you’ll feel underpowered while driving the car. You will also feel issues like rough idle and engine stalling.
The worst of all issue is the engine knocking and misfiring. If you continue to run with a faulty MAP sensor, these issues can decrease the average life of your engine.
Hence, you should not leave this issue unchecked. If you observe the above symptoms, act immediately and get your MAP replaced as soon as possible.
Frequently Asked Questions
How long can you drive with a bad MAP sensor?
You can drive 250 to 500 miles with a bad MAP sensor. However, this doesn’t mean that you should drive. If the symptoms have become worse, you should not even drive a single mile. A bad MAP sensor can reduce the life of your engine due to knocking and misfiring.
How to troubleshoot a MAP sensor?
You can look for signs described in detail above to troubleshoot a bad MAP sensor. A good course of action is to use an OBD2 scanner to check whether the MAP sensor has stopped working. If you run it for error codes, you’ll know exactly which sensor is malfunctioning.
What is the average lifespan of a MAP sensor?
All sensors, including the MAP sensor, are designed to last your engine’s lifespan. Unfortunately, MAP sensors usually fail after your car reaches 70,000 miles. If associated issues are left unchecked, it can also fail way before that.
What problems can a MAP sensor cause?
A bad MAP sensor can impact almost all parts of the engine. It starts from the intake manifold of your engine. If the MAP sensor goes bad, it can draw too much air into the intake manifold. This will disturb the perfect vacuum condition. The seal of the vacuum hose can get damaged, and the engine will not work correctly.
Can MAP sensor affect ignition & spark timing?
Yes, ignition and spark timing in intricate matter and can be affected by a bad MAP sensor. As described above in great detail, a faulty MAP sensor can bring too much or too little fuel into the combustion chamber. This can cause knocking and misfiring in your engine. In such a scenario, the spark and ignition timings are also affected.
Can the MAP sensor activate the limp mode?
Yes, the MAP sensor is a critical part of your car’s electrical system. If it malfunctions, the vehicle instantly goes into limp mode to protect other systems and components from further damage.
Can a bad MAP sensor throw code?
Yes, a bad MAP sensor can throw fault codes. The fault codes thrown in case of a bad MAP sensor are listed above. You can scan these fault codes with the help of an OBD2 scanner.