Symptoms of a BAD MAP Sensor
These are some of the symptoms your 2.4L Quad 4 GM car will experience with a BAD MAP Sensor:
- The Check Engine Light will be on with a MAP Diagnostic Trouble Code (DTC) stored in the Computer’s memory.
- If your 2.4L Quad 4 GM car is OBD II equipped, you’ll see DTC P0106 or P0107 or P0108.
- Your vehicle won’t start or will have a long cranking time before it starts.
- Black smoke coming out of the tailpipe along with really BAD gas mileage.
- The engine idles rough when running and has a lack of power when accelerated.
MAP Sensor Code Won’t Go Away
So you’ve tested the MAP Sensor and according to the test results, it’s good... But the CHECK ENGINE LIGHT keeps coming back on even after you erased the Diagnostic Trouble Code (DTC) from the Computer’s (PCM) memory. Well, here are a couple of suggestions that might inspire your next diagnostic move:
1
The MAP Sensor’s O-rings, the ones located on the Vacuum inlet nipple are missing or are too old and they’re not sealing properly. Visually check the O-rings and replace if necessary.
2
The Engine has several Cylinders with very low Engine Compression causing it to Idle Rough and thus producing low or erratic vacuum. For this I suggest a Compression Test.
3
The MAP Sensor is failing intermittently. Which means that it works fine most of the time, but every now and then... it doesn’t:
I have found that the best way to test these intermittents is to slightly tap the MAP Sensor with the handle of a Screw-driver and see if this tapping screws up the Voltage readings as I apply vacuum.
4
The MAP Sensor’s connector is BAD, usually the locking tab is broken and the connector has worked itself loose, causing an intermittent false connection.
5
Your Fuel Pump is starting to go BAD and is not sending enough fuel and/or fuel pressure up to the Fuel Injectors. I suggest a Fuel Pump Test.
The cool thing is that the Manifold Absolute Pressure (MAP) Sensor, on your vehicle, can easily be tested using only a Multimeter. Not only that, it can be accurately tested so that you can say, "Yes, it's BAD" or "NO", it's not BAD".
MAP SENSOR TEST 1: Verifying the MAP Sensor Signal with a Multimeter.
MAP SENSOR TEST 2: Verifying the 5 Volt Reference Supply.
MAP SENSOR TEST 3: Verifying the MAP Sensor is Getting Ground.
Symptoms of a BAD MAP Sensor.
MAP Sensor Code Won’t Go Away.
MAP SENSOR TEST 1:
Verifying the MAP Sensor Signal with a Multimeter
This first test will get the whole show on the road by first checking that the MAP Sensor is producing a MAP Signal or not. Depending on your results... you'll continue on to the next test or stop.
The instructions call for a Vacuum Pump. If you live here in the States and you don't have one... you can run down to your local AutoZone or O'reilly Auto Parts and rent one for free. If this option is not available to you and you're itching to get started, you can use the good ole' lungs (this will work... but I don't recommend it).
OK, this is what you need to do:
Remove the MAP Sensor from the Intake Manifold.
Connect your Vacuum Pump to the MAP Sensor’s vacuum nipple. If you disconnected the MAP Sensor, from its electrical connector to remove it from the Intake Manifold... reconnect it to it now.
Select Volts DC on your trusty Multimeter and probe the wire labeled with number 2 (in the image viewer).
The BLACK Multimeter Test Lead needs to be Grounded, preferrably on the Battery Negative Terminal.
When all is ready, turn the Key on but don’t start the Engine. This supplies the MAP with Power and Ground and your Multimeter should register 4.7 Volts DC.
Now, apply Vacuum to the MAP Sensor with the Vacuum Pump (or your mouth). You should see following DC Voltages at the following Vacuum values if you're using a Vacuum Pump:
1.) 0 in. Hg ...... 4.7 Volts.
2.) 5 in. Hg ...... 3.9 Volts.
3.) 10 in. Hg .... 3.0 Volts.
4.) 20 in. Hg .... 1.1 Volts.
Whether you're using a Vacuum Pump or the good ole' lungs, the important thing is that the Voltage should increase and decrease without any gaps or skips on the Multimeter. Repeat test steps 1 thru’ 5 several times.
OK, let’s take a look at what your Vacuum Pump Test results mean:
CASE 1: The Voltage increased and decreased smoothly and without gaps: This means that the Manifold Absolute Pressure (MAP) Sensor is good and not the cause of the MAP Sensor Code or problem on your GM 2.4L Quad 4. No further testing is required.
Now, if your vehicle still has the MAP Sensor code lighting up the Check Engine on your Instrument Cluster.. take a look at the section: MAP Code Won’t Go Away for more info.
CASE 2: Your Multimeter registered some Voltage, but not as indicated: This tells you that you have a BAD Manifold Absolute Pressure (MAP) Sensor on your GM 2.4L Quad 4. Replacing the MAP Sensor will solve the MAP Code issue (P0106, P0107, P0108)
CASE 3: Your Multimeter registered 0 Volts: This usually means that the MAP Sensor is fried. But further testing is needed to be absolutely sure, I suggest confirming that the MAP Sensor has power and ground. If both (power and ground) are present, the MAP is BAD. To test for power, go to MAP TEST 2.
MAP SENSOR TEST 2:
Verifying the 5 Volt Reference Supply
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Image 1 of 2
So far, in MAP TEST 1, you have verified that the MAP Sensor on your 2.4L Quad 4 GM car is not creating a Signal or the Signal is erratic
And so, in this MAP Sensor Test step, you’re gonna’ verify that the MAP Sensor is getting power, since without power it won’t work. This power come in the form of 5 Volts and the PCM (Powertrain Control Module = Fuel Injection Computer) is the one that provides this juice.
Since this circuit is directly connected to the PCM, be careful and don’t short this wire to Battery Power (12 Volts), or you run the risk of frying the PCM.
Alright, this is what you’ll need to do:
1
With your Multimeter still in Volts DC mode from the previous test and the Key On (but engine Off).
2
Probe the wire labeled with the number 1, in the image viewer, with the RED Multimeter Lead.
You can test for these 5 Volts with the MAP Sensor’s electrical connector connected to the MAP Sensor or not... just avoid probing the front of the connector.
3
Now ground the Multimeter’s BLACK Test Lead on the Battery’s Negative Post.
4
Your Multimeter should show you either:
1.) 5 Volts DC
2.) 0 Volts.
OK, now that the testing part is done... let’s take a look at what your results mean:
CASE 1: The Multimeter registered 5 Volts: This is the correct result and it’s starting to look like the MAP Sensor is BAD but you still need to check that the MAP Sensor is getting ground. For the ground test, go to MAP SENSOR TEST 3.
CASE 2: The Multimeter DID NOT register 5 Volts: This results lets you know that the MAP Sensor is not BAD, since without these 5 Volts DC, the MAP Sensor can not function.
Although it’s beyond the scope of this article to troubleshoot the cause of these missing 5 Volts, you have now eliminated the MAP Sensor as BAD. Resolving the issue that is keeping these 5 Volts from being supplied will solve the MAP Sensor issue on your 2.4L Quad 4 GM car.
MAP SENSOR TEST 3:
Verifying the MAP Sensor is Getting Ground
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Image 1 of 2
The next step (after verifying the MAP Signal and power circuit) is to make sure that the MAP Sensor on your 2.4L Quad 4 GM car has a good path to Ground. So, in this test step, you’re gonna’ verify that the MAP Sensor is getting ground using your Multimeter once again.
A word of caution: since this circuit is directly connected to the PCM, be very careful and don’t short this wire to Battery Power (12 Volts), or you WILL FRY the PCM.
Alright, this is what you’ll need to do:
1
With your Multimeter still in Volts DC mode from the previous test and the Key On (but engine Off).
2
Probe the wire labeled with the number 3 in the image viewer, with the BLACK Multimeter Lead.
It doesn’t matter if you probe this circuit (wire) with the connector connected to the MAP Sensor or not, but do not probe the front of the connector (if you decide to unplug the connector to test for this path to Ground).
3
Now connect the Multimeter’s RED Test Lead on the Battery’s Positive (+) Post.
4
Your Multimeter should show you either:
1.) 12 Volts DC
2.) 0 Volts.
OK, let’s take a look at what your results mean:
CASE 1: The Multimeter registered 12 Volts: This is the normal result and it means that the MAP Sensor your 2.4L GM car is fried and needs to be replaced.
Here’s why: In MAP TEST 1 and 2, you verified that the MAP Sensor is not producing the correct values (when you applied vacuum) and that it does have power. Since in this test step you have confirmed that the MAP Sensor does have a solid path to Ground... these results, interpreted together, indicate that the MAP Sensor is BAD.
CASE 2: The Multimeter DID NOT register 12 Volts: double check your Multimeter connections and repeat the test... if your Multimeter results still do not indicate 12 Volts, then the MAP is not fried and not the cause of the MAP Diagnostic Trouble Code (DTC) issue.
Here’s why: Without a good path to Ground, that the PCM provides internally, the MAP Sensor will not work. With this test result, you have eliminated the MAP Sensor as BAD.
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