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Symptoms of a Bad MAP Sensor, and How to Test One

Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology.

MAP sensor on footwell inside engine compartment.

MAP sensor on footwell inside engine compartment.

Bad MAP Sensor Symptoms

A bad manifold absolute pressure (MAP) sensor can upset fuel delivery and ignition timing. Depending on your vehicle model, your engine might experience one or more of these performance problems:

  • Rich air-fuel ratio
  • Lean air-fuel ratio
  • Surging
  • Poor fuel economy
  • It won't start
  • Lack of engine power
  • Stalling
  • Detonation and misfire

However, these symptoms are not exclusively symptoms of a failed MAP sensor. Sometimes, a bad sensor may trigger the check engine light (CEL). If a trouble code has been stored on the computer memory indicating a problem with the MAP sensor, it's a good idea to actually test the sensorm to confirm that the problem lies with the sensor and not some other related component.

What You'll Need to Troubleshoot a MAP Sensor

Troubleshooting a MAP sensor is a straightforward procedure using a digital multimeter (DMM) and a hand-held vacuum pump. If you don't have the pump, your local auto parts store may lend you one.

In the following sections, you'll find some important information about the sensor, what to pay attention to during your inspection, and a simple MAP-sensor test procedure. Keep in mind that these tests apply to gasoline, four-cycle internal combustion engines without a turbo or supercharger. If necessary, consult the vehicle repair manual for your specific model.

Answers You'll Find In This Article

  1. What Does a Map Sensor Do?
  2. Does My Car Have a MAP Sensor?
  3. P0105 and Other MAP Trouble Codes
  4. MAP Sensor Location
  5. How to Test a MAP Sensor
  6. Checking the MAP Sensor Reference Signal
  7. Sensor Voltage Drop Reference Table
  8. Testing a Digital MAP Sensor
  9. MAP Sensor Replacement
  10. Should I Replace the MAP Sensor?
Inspect the map sensor wires for damage during your diagnostic.

Inspect the map sensor wires for damage during your diagnostic.

I. What Does a Map Sensor Do?

Basically, a MAP sensor reads the amount of air pressure in relation to vacuum inside the intake manifold, either directly or using a vacuum hose. Then, it translates this pressure into a voltage signal that the sensor feeds to the power control module (PCM), your car's computer.

The sensor uses a 5 volt reference signal that comes from the computer to return the signal.

Changes in vacuum or air pressure in the intake manifold varies the electrical resistance in the sensor, increasing or reducing the signal’s voltage to the computer.

The PCM uses the MAP sensor’s information along with input from other sensors to adjust fuel delivery to the cylinders and ignition timing according to current engine load and speed.

Some vehicles use a mass air flow sensor (MAF) instead of a MAP sensor. Some use both.

Some vehicles use a mass air flow sensor (MAF) instead of a MAP sensor. Some use both.

2. Does My Car Have a MAP Sensor?

Instead of a MAP sensor, most modern vehicles use a mass air flow (MAF) sensor that the computer uses to calculate air flow along with engine rpm.

Some vehicles come equipped with both a MAP and MAF sensor, usually forced induction systems like turbocharged and supercharged models.

Sometimes, the MAP sensor is used to monitor EGR operation, and doubles as a back up to the MAF sensor.

If you need information regarding your vehicle, consult the repair manual for your particular make and model. You can buy an inexpensive Haynes manual from Amazon. These manuals come with procedures for many maintenance, troubleshooting and replacement component projects. So the manual practically pays for itself after the first maintenance or repair project.

Caution: When Checking Voltages

Use the repair manual for your particular vehicle make and model for diagnostic value specifications.

Use a scanner to download diagnostic trouble codes from your car computer.

Use a scanner to download diagnostic trouble codes from your car computer.

3. P0105 and Other MAP Trouble Codes

Sometimes, a malfunction in the MAP sensor or its circuit will trigger the check engine light (CEL).

Scanning the computer, you may find a P010X series of codes stored in memory.

Here is a brief description of these codes:

  • P0105: MAP sensor circuit malfunction.
  • P0106: MAP sensor circuit, range or performance malfunction.
  • P0107: Circuit, low input.
  • P0108: MAP sensor circuit, high input.
  • P0109: MAP sensor circuit, intermittent failure.

Other related codes include P0068 and P0069.

You can find a more detailed description of these codes in your vehicle repair manual or by searching on-line.

Carefully read the description of the code you've found and what the potential fault resulted from this code.

Remember that even though the code points to the potential problem, the particular circuit or component involved may not be at fault. Instead, a related component may have triggered the code.

For example, in many applications a leaking vacuum hose or a bad throttle position sensor (TPS) may cause a trouble code that points to a faulty MAP sensor.

Troubleshooting the sensor is the only way to determine whether the sensor or part is actually bad.

On some models, you only need to remove a couple of screws to get to the sensor.

On some models, you only need to remove a couple of screws to get to the sensor.

4. MAP Sensor Location

The MAP sensor is usually located in a few key places around the upper engine bay area.

  • Intake manifold. Under or near the throttle body; this is perhaps the most common place.
  • Inner fender.
  • Firewall.
  • Air cleaner assembly.
  • Under the dashboard.

The sensor may connect to the intake manifold with a vacuum hose or directly, by sitting on top of the intake manifold.

Caution: When Using a DMM

Always use a digital multimeter with a minimum 10 megaohms of impedance, to prevent damage to sensitive electronic and electrical devices in your vehicle.

Use a digital multimeter with at least 10 Megaohm impedance to troubleshoot the MAP sensor.

Use a digital multimeter with at least 10 Megaohm impedance to troubleshoot the MAP sensor.

5. How to Test a MAP Sensor

When testing a MAP sensor, first make a preliminary check.

The sensor connects to the intake manifold with a rubber hose, depending on your particular application; otherwise it connects directly to intake.

When problems arise, it's more likely that the vacuum hose has failed. Within the engine compartment sensor and hose are exposed to high temperatures, potential contamination from oil and fuel, and vibration that can affect their operation.

Check the vacuum hose for:

  • kinks
  • loose connections
  • cracks
  • swelling
  • softening
  • hardening

Then, check the sensor's body for damage and make sure the electrical connection is tight, clean, and the wiring is good.

Compare your readings to specifications listed in your vehicle repair manual.

Compare your readings to specifications listed in your vehicle repair manual.

6. Checking the MAP Sensor Reference Signal

The MAP sensor uses a three-wire connector. You need to identify the signal, reference, and ground wires using your vehicle repair manual.

Checking for reference voltage:

  1. Turn the ignition key to the On position but don't start the engine. This will allow the computer to supply a reference voltage to the MAP sensor.
  2. Set your multimeter to about 10V on the direct current (DCV) scale.
  3. Backprobe the reference wire at the connector. The readout should show 5 volts or close to it.

    • If your voltage is lower, visually inspect the connector and wire between the sensor and the PCM for damage. You may need to measure this voltage on the same wire but at the computer side.
      • If you still get a low voltage at the computer side, then you need to check the computer.
      • Otherwise, if the voltage rises to 5 volts, than there is a problem in the wire between the computer and sensor.
  4. Turn off the ignition key.

Checking for signal voltage:

  1. Unplug the sensor’s vacuum hose.
  2. Connect a hand-held vacuum pump to the sensor, but don’t apply vacuum to the sensor yet.
  3. Backprobe the signal on the electrical connector using the red DMM probe. Connect the black DMM probe to ground using any metal surface on the engine or the battery negative post.
  4. Turn the ignition switch to the On position, but don't start the engine.
  5. Your voltage reading should be between 4.6 and 5 volts.
  6. Apply 5 in-Hg of vacuum to the sensor. The readout should be about 3.75 volts.
  7. Now apply 20 in-Hg of vacuum to the sensor. The voltage should be about 1 volts.

Your readings may vary slightly, depending on altitude and current weather conditions.

NOTE: On some repair manuals, you're asked to check resistance while applying vacuum to the sensor. Follow the instructions in your particular manual and compare your results to listed specifications.

The following table shows the approximate MAP sensor return-signal voltage drop when a specific amount of vacuum is applied. Use these values as a general reference.

Also, watch the video towards the end of this post that gives you a visual reference about troubleshooting an analog MAP sensor using a DMM and a hand-held vacuum pump.

MAP Sensor Voltage Drop Reference Table

VacuumVoltage drop

5 in-Hg

0.7 to 1.0 Volts

10 in-Hg

1.3 to 1.9 Volts

15 in-Hg

2.0 to 2.8 Volts

20 in-Hg

3.0 to 3.8 Volts

You can use an oscilloscope or a DMM with a frequency function included to test a digital MAP sensor.

You can use an oscilloscope or a DMM with a frequency function included to test a digital MAP sensor.

7. Testing a Digital MAP Sensor

If your vehicle uses a digital MAP sensor, instead of an analog one, you can also test it using a DMM that can measure frequency signals.

  1. First, set your multimeter to about 100 or 200 hertz.
  2. Unplug the vacuum hose form the sensor and plug in a hand-held vacuum pump to the sensor's vacuum port.
  3. Backprobe the signal and ground wires at the sensor electrical connector.
  4. Turn the ignition key to the On position but don't start the engine.
  5. Make a note of the voltage, duty cycle and frequency readings on your meter.
  6. Now, apply about 18 in-Hg of vacuum to the sensor, and note the voltage, duty cycle and frequency readings on your meter.

    • Your sensor should have about the same voltage and duty cycle readings in both tests.
    • Without vacuum applied, the sensor should have about 160 hertz.
    • With vacuum applied, the sensor should drop to about 100 hertz.

Consult your vehicle repair manual for specifications.

On some models, you may need a Torx screwdriver or bit to remove the MAP sensor.

On some models, you may need a Torx screwdriver or bit to remove the MAP sensor.

8. MAP Sensor Replacement

Replacing a MAP sensor is a straightforward operation. Sometimes the sensor is readily accessible and you can replace it in about 5 minutes or less; other times, you may need to remove one or more accessories to gain access to it.

Regardless, the following procedure will help you replace the sensor. If the sensor in your vehicle uses a vacuum hose, it's a good idea to replace it along with the sensor.

  1. First, locate the sensor. You may find it:

    • around the top of the intake manifold
    • near the firewall
    • sitting next to the throttle body or under it
    • mounted on the tower on the well

    Consult your vehicle repair manual, if necessary,

  2. Disconnect the negative battery cable and secure the cable away from the post.
  3. Depending on the location of the sensor, you may need to remove one or more bolts or Torx screws.
  4. Unplug the sensor electrical connector. The connector may be securely locked. If so, depress the locking tab and then unplug the connector.
  5. Detach the vacuum hose from the sensor, if it has one.
  6. Detach the vacuum hose from the other end.
  7. Use the old vacuum hose as a guide to trim the new one to proper length, if necessary.
  8. Connect the new hose to the fitting on the intake manifold side, and the other end to the new MAP sensor.
  9. Plug in the sensor electrical connector. Make sure the connector locks to the sensor.
  10. Mount the new sensor in place.
  11. Connect the negative battery cable to the battery post.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: Is there a reset button you need to do when putting in a new MAP sensor on a 2011 Ford Fusion set to shut off the check engine light?

Answer: On some models, it's possible to disconnect the battery to turn off the check engine light. But I believe you need to erase the code in order to reset the light using a scanner. Otherwise, it'll keep coming back, even if you disconnect the battery. Try Autozone first. If not, stop by a local shop. They'll charge you though. Hope this helps.

Question: I have a dodge dart 2014 gt, it turns off sometimes running and there comes a time where it does not start. Twice he has turned on the code p2172 and replaced the part of the throttle system and continues with the same fault?

Answer: Probably the idle air control (IAC) motor is getting stuck, allowing too much air to into the system. Make sure the throttle plate is not getting stuck either. This other post may help here:

https://axleaddict.com/auto-repair/Why-My-Car-Stal...

Question: I have a 06 Altima that keeps giving a P0420 code for the oxygen sensor. I replaced both sensors and crank position sensor, which we had a code. The crank code went away, the oxygen sensor will not. I previously replaced catalytic converter 2 times, then both oxygen sensors and code is still on for the 02 sensor. What could the P0420 code mean?

Answer: Code P0420 points to the downstream oxygen sensor. According to the code, the sensor is reading too much oxygen in the exhaust stream. There could be a leak in the exhaust system, misfire, the faulty fuel injector (too much fuel), faulty fuel pressure regulator (increased pressure), or even a fault in the downstream oxygen sensor circuit.

Question: We have a 08 Charger with a Hemi. We have replaced the fuel pump, throttle body, crankshaft sensor, and peddle assembly. What else can we do?

Answer: If you are having problems with fuel delivery or spark have the fuel or ignition system tested. It’s not a good idea to replace components without troubleshooting the specific components.

This other post can help you start troubleshooting the fuel system:

https://axleaddict.com/auto-repair/How-to-Test-a-F...

Check you have a good spark. If you haven’t already, check for trouble codes, even if the check engine light is not coming on. There could be pending codes that can help you figure out what component/system is giving you problems.

Question: I have a 2004 Dodge Dakota. Engine light came on. Truck started to kind of spit and sputter. O2 codes came up along with a heat code. I replaced all 4 sensors. It ran great. Now 2 months later it's doing the same thing. No one can figure it out. I have been told the computer may be bad. Any ideas?

Answer: The engine might be running in open loop because of the code and running rich. Check for foul spark plugs that might be causing misfires. If you still have the old ones, check those sensors for carbon buildup. There can be a problem with the catalyst that might be affecting one or more O2 sensors. Also, the problem could be in the circuit to the heating element or the sensor themselves.

Question: When it's less than 25 degrees Fahrenheit, my 2013 Ford F250, even when completely warmed up, doesn’t have any power until 2000 RPMs. Then it gets normal power and pushes fuel like normal again. What could be the cause of this?

Answer: There could be a problem with a sensor. You may want to check the temperature sensor. It may have become lazy and giving inaccurate readings to the ECU and miscalculating fuel needs. Download trouble codes, even if the engine light is not on. A pending code may be stored in memory that can help you here.

Question: I have a 2004 Buick LeSabre. If my sensor has a crack in it, does it necessarily mean it's bad? I ask because I just had to replace head gaskets. Is it due to the sensor?

Answer: You can test the sensor to make sure it's operating properly. If it already has a crack, it's better to replace it. The sensor only measures vacuum or intake pressure and it won't cause damage to the head gaskets.

Question: My 2002 Town and Country is showing a misfire in cylinders one and four. It runs rough at idle, backfires under load or acceleration, surges when trying to hold at 4000 RPM and park. Is the MAP at fault for my Town and Country's cylinder issues, or is something else going on?

Answer: There could be several reasons for a misfire. Your misfire is located on the 1 and 4 cylinders; this can make it easier to locate the fault. Check out this other post. it may help you find the source of the misfire:

https://axleaddict.com/auto-repair/Engine-Misfires...

Question: I have a 1989 Buick Le Sabre and have replaced my MAP twice. It runs good a few weeks and then I have problems again with symptoms of stalling and low power. I’m okay if I keep my foot in the gas at all times. The only code that comes up is the MAP sensor. Any ideas why my sensor keeps failing? Or what else should I look at?

Answer: The problem might be in the connector or circuit for the MAP sensor. You may need the repair manual for your model to identify wires. Check the vacuum hose as well. These other posts may help too:

https://axleaddict.com/auto-repair/Why-My-Car-Stal...

https://axleaddict.com/auto-repair/What-Causes-Low...

Question: I have Suzuki XL7 2007. It was fine but at a certain point the engine light came on. My problem is that when I drive, it downshifts while stopping at a traffic light or sometimes delayed shifting response from lower gears while accelerating or sometimes even random shifting between gears. For example, it sticks in gear 4 and when I try to downshift from that gear, it goes to gear 2. It skips gear 3. Could the PCM module or MAP to cause my Suzuki to skip gears when downshifting?

Answer: Usually, delay in shifting is caused by the clutch for those specific gears. However, other problems can also lead to this issue, like a leaking hydraulic circuit or a sticking spool valve in the valve body. Also, you may want to try checking the vacuum. If it fluctuates or has incorrect pressure, there could be your problem. This other post may help:

https://axleaddict.com/auto-repair/Use-a-Vacuum-Ga...

You may need to bring the vehicle for testing to identify the cause of the problem.

Question: Where is the MAP sensor located?

Answer: It depends on your particular model, but look at a location, usually, in the upper area of the engine compartment: near the strut tower, intake manifold, throttle body, even near the headlight assembly. Sometimes you need to remove the air cleaner assembly to gain access to it. The auto parts person at your local area may be able to tell you the location in your particular model.

Question: I have a 2000 Grand Cherokee Limited 4.7 2x2. Since I bought it, I’m having the problem of it dying while driving and leaving me stranded for 5 minutes to 5 hours. As mysterious as it dies (no warning or sign or engine lite), it’ll start back up and drive normally till the next time. It seems worse in the summer as it's cold here and she hasn’t died in 18 days! Which is miraculous as it goes days with dying 2-8 times a day or go days without dying. Can you show me or tell me what to do!!?

Answer: This other post may help:

https://axleaddict.com/auto-repair/Why-My-Car-Stal...

© 2018 Dan Ferrell

Comments

Dan Ferrell (author) on April 01, 2020:

I believe the sensor is located on one side of the valve cover or towards the top of the valve cover and front of the engine. Hope this helps.

SHAWN on March 31, 2020:

Good evening Dad this is Shawn having a hard time locating the map sensor on a 1987 Buick Electra 3.8

Dan Ferrell (author) on March 20, 2020:

This other post may help:

https://axleaddict.com/auto-repair/Engine-Backfire...

Samson on March 19, 2020:

Good day sir when driving the car the car will be shooting when you try do Accelerate the car the car will be shooting what can I do to solve the problem

Dan Ferrell (author) on November 25, 2019:

A few components and sensors that might cause a vehicle to loose power may include: clogged air or fuel filter, Oxygen sensor, MAF sensor, and TPS sensor. Also, check ignition timing and, if necessary, timing belt. This other post may help too:

https://axleaddict.com/auto-repair/What-Causes-Low...

I have a 91 mustang will not excelarate on November 24, 2019:

I have a 91 mustang will not excellarate

Dan Ferrell (author) on August 16, 2019:

The code is for the model with the 6 Cylinders V 3.0L engine. If you have the 4 cylinder engine, check the air cleaner assembly. There could be a leak that is upsetting the air-fuel mixture.

Skylar on August 16, 2019:

I have a 1992 toyota camry i keep getting code p0104 for my check engine light but i do not have a maf sensor. My car idles fine when cold as soon as it warms up it idles rough drives decent sometimes it has a gas smell and poor fuel economy and when i stop at a light my cars rpms is about 400rpm

Dan Ferrell (author) on August 12, 2019:

This other post may help:

https://axleaddict.com/auto-repair/P0300-Random-Mi...

Shawn Brown on August 12, 2019:

I have a Cadillac Escalade esv 03 and i keep getting a code P0300 i put new plug in wire can someone help me with my problem it's been down for 5 week please help.

Mukabya Samuel on February 13, 2019:

Thanks

Dan Ferrell (author) on January 08, 2019:

The best way to know is to test the sensor(s). You may want to check the procedure in the vehicle repair manual for your particular model. If you don't have the manual, check the reference section of you local public library. Also, scan the computer memory for trouble codes using a code reader. Hope this helps.

Jmontman on January 08, 2019:

I have a 1989 Bronco 2 with the 2.9 v6. I’m getting a skip or sputtering every few seconds. But it’s not bad on certain days. Depending on the weather it either runs smooth or rough. This is what makes me think of the MAP sensor. I’m pretty sure that I need o2 sensors but after watching a few videos I’m wondering if I should just replace all the sensors. Any opinions on a solution?