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Old 03-25-2013, 09:26 PM
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Default How do you test the map sensor

I'm getting code 34 so I went to youtube and it shows hooking my meter to the middle green/black stripe wire and to ground and with the key on I should read 5v I'm reading .12v so I checked the ECM fuses and their fine. Am I doing it correct? how do I check if the ground wire is broken somewhere?
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Old 03-26-2013, 03:35 AM
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Old 03-26-2013, 04:12 AM
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[I]I found it.

http://troubleshootmyvehicle.com/gm/...timeter-test-1





[/included how to interpret them.

OK, to get this show on the road, this is what you need to do:

1

Disconnect the MAP Sensor from its Vacuum Hose. On your specific vehicle, you may have to physically remove the MAP Sensor from its mounting to disconnect it from its Vacuum Hose.


2

Connect your Vacuum Pump to the MAP Sensor’s vacuum nipple. If you had to disconnect the MAP Sensor from its electrical connector to remove it, reconnect it to it now.


3

With your Multimeter in Volts DC mode probe the wire labeled with the number 2 (in the image viewer).

Remember, the MAP Sensor must remain connected to its 3 wire connector.


4

Ground the BLACK Multimeter Test Lead directly on the Battery Negative Terminal.


5

Turn the Key on but don’t start the Engine. At this point your Multimeter should register 4.7 Volts DC.

Now, pump the Vacuum Pump to apply Vacuum to the MAP Sensor. The Multimeter should register the following Voltages at the following Vacuum values (they may differ a little on your specific 2.8L, 3.1L, 3.4L GM car or mini-van):

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.

Repeat this test step several times and each time, you should see the same values on your Multimeter.


OK, let’s take a look at what your Vacuum Pump Test results mean:

CASE 1: Your Multimeter registered the indicated Voltages as you applied Vacuum: 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 2.8L, 3.1L, or 3.4L car or mini-van. 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 register Voltage, but it did not increase or decrease as you applied Vacuum: This confirms that the Manifold Absolute Pressure (MAP) Sensor on your GM car or mini-van is BAD. Replacing the MAP Sensor will solve the MAP Code issue (P0106, P0107, P0108 or 33, 34)

CASE 3: Your Multimeter registered 0 Volts: This usually means that the MAP Sensor is fried. 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.



the MAP Sensor with a Multimeter (GM 2.8L 3.1L, 3.4L)
.

.





How to Test the MAP Sensor with a Multimeter
(GM 2.8L 3.1L, 3.4L)
Details Written by Abraham Torres-Arredondo

Page 1
Page 2
Page 3


MAP SENSOR TEST 2: Power Supply








Enlarge




So far, in MAP TEST 1, you have verified that the MAP Sensor on your GM 2.8L, 3.1L, or 3.4L car or mini-van is not creating a Signal or the Signal is erratic

An 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 GM 2.8L, 3.1L, or 3.4L car or mini-van.

MAP SENSOR TEST 3: Ground Supply








Enlarge




The next step (after verifying the MAP Signal and power circuit) is to make sure that the MAP Sensor on your GM 2.8L, 3.1L, or 3.4L car or mini-van 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 GM 2.8L, 3.1L, or 3.4L car or mini-van 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.

the MAP Sensor with a Multimeter (GM 2.8L 3.1L, 3.4L)
.

.





How to Test the MAP Sensor with a Multimeter
(GM 2.8L 3.1L, 3.4L)
Details Written by Abraham Torres-Arredondo

Page 1
Page 2
Page 3


Symptoms of a BAD MAP Sensor

These are some of the symptoms your GM 2.8L, 3.1L, or 3.4L car or mini-van will experience with a BAD MAP Sensor:

1

The Check Engine Light will be on with a MAP Diagnostic Trouble Code (DTC) stored in the Computer’s memory.


2

If your GM 2.8L, 3.1L, or 3.4L car or mini-van is OBD II equipped, you’ll see DTC P0106 or P0107 or P0108. If your GM 2.8L, 3.1L, or 3.4L car or mini-van is 1994 or older, you see DTC’s 33 or 34.


3

Your vehicle won’t start or will have a long cranking time before it starts.


4

Black smoke coming out of the tailpipe along with really BAD gas mileage.


5

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.

I]
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Old 03-26-2013, 06:18 AM
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the code 34 is telling you the voltage is low,,
try test 2,, see if you have 5v on the grey wire??
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Old 03-26-2013, 06:30 AM
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Quote:
Originally Posted by JJLT1 View Post
the code 34 is telling you the voltage is low,,
try test 2,, see if you have 5v on the grey wire??

I will try them all if needed I have a vacuum pump also. The map sensor was replaced when I did my engine swap and before I knew how bad Autozone parts are so it's probably bad after a year. Nothing else has held up unless I already changed it to quality parts. Oreilly's has one for $39.00 but the other five they offer are from $70.00 to $138.00 stay away from the $39.00.
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Old 03-26-2013, 09:02 AM
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Buy the best and be done with is what I would do not to be stranded some where with a cheap part
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Old 03-26-2013, 10:38 AM
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if you still have the original map sensor?? try it, see what happens..
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