The pressure sensor in your Chevy Silverado is mounted to the intake manifold. This sensor is also known as the Silverado MAP Sensor, or manifold absolute pressure sensor. This unit is meant to read the barometric pressure of the air entering your engine. Your Chevy Powertrain Control Module uses this data to deliver the right amount of fuel and spark to your engine.
When your Silverado MAP Sensor starts to go bad, you are going to have some issues with your engine to say the least. Your idle may be rough but more than likely your Silverado will run rich or use too much fuel. If you don’t correct this issue, the excessive hydrocarbons can elevate your exhaust gas temperature to the point of your catalytic converter failing.
If you think your Silverado MAP sensor is going bad, this How To Guide can help you test it. Today I’ll be showing you how to test the manifold absolute pressure sensor in a 2007 Chevy Silverado with a 5.3 liter engine in it. In order to complete this test however you will need to use a digital multimeter to read the voltage at the engine harness.
The three wire MAP sensor in your vehicle is mounted to the top of the intake manifold. It uses a ribbed grommet to help secure and seal the air pressure, and to prevent your engine from running lean.
Symptoms of a failed Silverado MAP Sensor
When this pressure sensor goes bad your 5.3 liter engine will have several problems or symptoms that can cause driveability issues. Here’s some of the more common symptoms from a bad MAP sensor.
- Harsh shifting transmission points
- Silverado engine running rich ( too much fuel )
- Bad gas mileage
- Inconsistent shift points
- Hesitation during acceleration
- Check Engine Light ON
When your check engine light turns on in your Silverado instrument cluster, you’ll need an OBDII scan tool to retrieve the stored codes. To begin this DIY tutorial, we’ll begin by checking the Silverado MAP Sensor for power.
Checking the Silverado MAP Sensor for Power
Open your Silverado hood and locate the MAP sensor, which is connected to the intake manifold. Unplug this MAP harness and the wire you’ll be testing first is PIN A on the ENGINE harness side. Make sure your key is inserted and turned to the “ON” position. There should be around 5 volts of DC power here at this wire.
If you have power here, great the next wire to check is the low reference ground wire. This is the wire that connects to PIN C, and if you’ve got a ground here then great your Silverado MAP Sensor is getting what it needs to operate.
Chances are now that your MAP sensor OBDII trouble code is still around, even after you’ve cleared it. If you know that your pressure sensor is getting power and ground but the trouble code is still present, you need to test the Silverado MAP Sensor signal.
This is done by reconnecting the MAP sensor connector, and using a vacuum pump to the port of the pressure sensor. You can purchase one of these at your local auto store, or simply pick up a Mighty Vac pump.
Reconnect the Silverado MAP Sensor harness and the wire you will need to read is the one that’s connected to PIN B. This wire is your signal wire, and you’ll be using the hand pump to deliver vacuum to the MAP sensor inlet.
With the key turned to the “ON” position you should see between 4.5-4.8 volts of DC signal at this wire. Remember that this part of the test may vary but as long as you are close to these readings your Silverado MAP Sensor is okay. Now apply 5 in. Hg of vacuum to the MAP inlet, at this reading you should have between 4.1 and 3.9 volts of DC signal. Increase the vacuum to 10 in. Hg and at this reading you should have between 3.0 and 2.8 volts.
If your Silverado MAP Sensor does not respond with this range of voltage, it’s time for a pressure sensor replacement. Have any questions about our How To test a Silverado MAP Sensor guide? Leave them for us below and let us know!
When testing my map sensor I noticed that prong B is giving Nothing. It seems I’m not getting any signal. I did have 5 volts on prong A but nothing on signal prong. My truck drove better last week when I unplugged the map while my truck was running. This is why I tested it. What do I do if the sensor is good but my vehicle is not giving info to the computer?
Nicholas, sounds like you have a break in wiring continuity, which isn’t a good time. Start by using a multimeter to find and repair the break in your wiring for your Silverado MAP sensor
I replaced the sensor, with a oem part from chevy, I removed the code, p0107, engine is off now, but still have the same vehicle running issues. Do I have to reset the Tru k computer?
I would check the harness first for breaks or issues Louis.
I bought a 2001 Chevy 1500 4.8L from a salvage yard for $300.00. The person or persons that owned it before me had become frustrated from a few shorts, that quickly drained the battery on occasions, and a few open wires not making contact also. Needless to say their frustration led them to just start cutting bundles of wiring at a time. Had i mot been not only a hot rodder all my life but a retired engineer and union electrician I wouldn’t have undertaken such a job but thanks to a few gadgets and tricks I learned throughout the years I eventually tracked the basics down and ended up driving the thing. To my surprise I repaired enough the cruise control even started working the other day.
If you don’t have one invest in a cheap wire tracer. Its audible sound will stop right where the break is im a wire.
I just dropped by to see which terminals were what on my new adventure. Thanks for the info and if you could would you tell me what acts simular to the security system start and die but if i pump the throttle it will stumble sometimes. Most times if i have a fresh battery and get some rpm’s up it clears out. It also does it on foggy or real humid days.
Thanks ahead of time.
Dan G.
4.3. My bad
I have a 99 Chevrolet Silverado 4.8 l motor I have nothing at the map sensor plug one on this illustration has three white plugs and has five
Hey there Randy,
can you take a pic of tha harness and post it? its a 3 plug harness? Does it look OEM?