CEL CODE # P0107 please help!!!

Hello All,

First off let me say thanks for reading and checking out. I bought a 99 Malibu 4 door with the 3.1l. so far it has an abs light ( no big deal ), and a Brake light ( kinda strange ). However my issue is CEL code # p0107 MAP sensor.I thought Id run to pull apart and just replace the sensor. I bought two of them same thing.
So then I thought I'd do so research on this and see what I can find out. To make a real long story short I found out that there is no power to any wire on the sensor. Does anyone know what wire comes from the computer (PCM) to this MAP sensor? that why I can check the PCM for power going to the MAP sensor? Please let me know any thoughts or info that can help. Thank you all in advance. Have a HAPPY EASTER:) :runaround:

The Map sensor is a 3 wire sensor....5v, ground , and signal wire....If you have no voltage anywhere, it means you have no 5v voltage....either an open wire between the PCM and the sensor or bad PCM......I am leaning towards a broken wire(could be broken inside the insulation).....the 5v and ground are the outside wires(signal wire is the middle wire)........the ground will be a black wire.....

Thanks Tech II. I was using the ground from the battery to Check for voltage, and could not find anything. Today I will try the other way and use the power from the battery to check the ground. I know the there is no voltage. Do you know if that wire will be the same at the pcm as it is at the sensor? I'm going to pull the pcm and see if I can figure out which wire it is, and check at the pcm for correct voltage. Thanks again for the quick response.

here is my most recent update.
I have checked all wires for power again. I then ran the positive wire of the tester to the positive side of the battery, then tested for ground. I did then show 12 volts to the tester.
So I do know that one wire is a good ground. Then the middle wire shows five volts with the ground wire hooked to the sensor lead, and the other wire going to the battery. Does this mean that my voltage that should be coming into my sensor is showing a ground, or would this be the return wire going back to tyhe pcm? I'm pretty good with wiring, however do not understand this. Please all let me know your thoughts. I'm wondering if this is a pcm issue. Thanks all for your help.

here is my most recent update.
I have checked all wires for power again. I then ran the positive wire of the tester to the positive side of the battery, then tested for ground. I did then show 12 volts to the tester.
So I do know that one wire is a good ground. Then the middle wire shows five volts with the ground wire hooked to the sensor lead, and the other wire going to the battery. Does this mean that my voltage that should be coming into my sensor is showing a ground, or would this be the return wire going back to tyhe pcm? I'm pretty good with wiring, however do not understand this. Please all let me know your thoughts. I'm wondering if this is a pcm issue. Thanks all for your help.

hard to under stand your testing . place the voltmeter ground lead on the battery ground or the alternator case. then with engine running measure the map voltages.

5volts power input/1.2volts signal out put/black wire 0 volts.

1.2 volts is normal reading @normal idle RPM..................if the signal voltage of 1.2 volts DC is 0 or more than 2 volts the engine has problems or the MAP is defective.

if you have no volts on the MAP input power of 5 volts then the wiring is most likely bad.

before measuring this MAP place the voltmeter positive probe on the battery positive so that you know the ground wire has a good connection ..

Thanks J cat,

Thats kinda what i was saying. I tested everything with a multimeter the ground to the ground side of the battery, and tested for any kind of voltage anywhere. I got nothing..

I then decided to make sure that the ground was good and reverse the wires. Connecting the ground to the sensor leads, and the positive side to the hot side of the battery.

I found that I have a good ground. While testing this way with the ground side of the multimeter going to the middle wire of the sensor lead or plug, and the positive side going to the hot side of the battery it shows 5volts. So is that the signal wire? and should it test showing voltage hooked up this way?

Hooked either way the third wire shows nothing. please let me know if that helps you understand what im talking about.

Thanks J cat,

Thats kinda what i was saying. I tested everything with a multimeter the ground to the ground side of the battery, and tested for any kind of voltage anywhere. I got nothing..

I then decided to make sure that the ground was good and reverse the wires. Connecting the ground to the sensor leads, and the positive side to the hot side of the battery.

I found that I have a good ground. While testing this way with the ground side of the multimeter going to the middle wire of the sensor lead or plug, and the positive side going to the hot side of the battery it shows 5volts. So is that the signal wire? and should it test showing voltage hooked up this way?

Hooked either way the third wire shows nothing. please let me know if that helps you understand what im talking about.

the ground lead of meter goes to ground. the positive red probe of meter goes to the MAP sensor wires to be measured. you do not put the meter on the battery positive when measuring the MAP voltages..

black is ground ///////////middle is output \\\\\\\\\ wire on the other end is the voltage input of 5 volts my be pink ..

I understand that you shouldn't test this way when testing for voltage. I just don't understand why, When I do test backwards it shows voltage? I have a friend that owns a shop, and he said that he will run the diagnosis on it for 40 bucks. I will just have to wait to get it there. or When I can get it there. I was considering trying a PCM, but doesn't sound like that would be it. Everything else seems to be working fine.

[quote=spike1269;7161015]I understand that you shouldn't test this way when testing for voltage. I just don't understand why, When I do test backwards it shows voltage? I have a friend that owns a shop, and he said that he will run the diagnosis on it for 40 bucks. I will just have to wait to get it there. or When I can get it there. I was considering trying a PCM, but doesn't sound like that would be it. Everything else seems to be working fine.[quote]...


Well since you do not understand why , I suggest if you plan on making repairs / testing that you take a basic electricity course. this will explain all this stuff. You will then be able to save money with knowing this type work. What I do not understand is why you do not follow my instructions ? perhaps you should bring to a repair shop and have this all checked out. where did you get PCM replacing for this code ? that would be like fixing the problem by purchasing another vehicle.

Hello Jcat, Thank you for the response. I know see why the other wire is testing this way. This is my signal wire. I Was testing for a ground when I found that the signal wire is reporting voltage when testing that way. I know now that it is just the voltage wire is dead. I have tried testing it as a ground, just to see if it was going to ground. The voltage wire (hot lead to Map) is not showing anything (no power or ground). This should be the same color wire at the pcm correct?

I'm going to unbolt the pcm and see if I can find this wire and test for voltage at the PCM. This should tell me if the wire is pinched beyond where I can see it.

I dont believe it is the PCM do to it did in fact trouble shoot that the MAP circuit is bad, or has a fault.

Hello Jcat, Thank you for the response. I know see why the other wire is testing this way. This is my signal wire. I Was testing for a ground when I found that the signal wire is reporting voltage when testing that way. I know now that it is just the voltage wire is dead. I have tried testing it as a ground, just to see if it was going to ground. The voltage wire (hot lead to Map) is not showing anything (no power or ground). This should be the same color wire at the pcm correct?

I'm going to unbolt the pcm and see if I can find this wire and test for voltage at the PCM. This should tell me if the wire is pinched beyond where I can see it.

I dont believe it is the PCM do to it did in fact trouble shoot that the MAP circuit is bad, or has a fault.

with the meter red probe not seeing any voltage on the map middle signal wire and the other end wires then the wiring is most likely the problem . you need 5volts to the MAP to get it to work no power to MAP it will do nothing.
I doubt the PCM is bad these things are usually from rough handling of the wire harness . wires used by GM now are very fragile.

hello jCat,

So I unhooked the battery, exposed and unbolted the PCM. Sprayed all contacts with an electrical contact cleaner. Then hooked up the new (used) MAP sensor, hooked up the PCM and bolted back in. Then once again connected the battery. I do not have a check engine light now, which in the past I was not able to clear.

As of now I'm not sure if it is fixed, however I do not have a light. The car seems to be running better from what I can tell.

Do you know how long the 99 Malibu 3.1 SFI--PCM takes to run through its cycle, so that it would show the CEL or SES light ?
THANK YOU FOR ALL YOUR HELP. I will keep you informed.

Well, It seemed to do better the first the car ran. As soon as I shut it off, then restarted the car the CEL was back on. I cleared the code it went away then, as soon as I re-started the car it came back. The one voltage wire still does not have any power. I looked at the PCM wiring, and it looks a little to complex for me. Do you have any ideas? please let me know if you come up with anything.

Take a needle and probe the middle wire to the MAP sensor, about 5-6" away from the connector......ground your meter, and attach the other lead to the needle.......

Turn key to on....should read 5 volts.....start vehicle, voltage should drop to around 1 volt.....

If no reading at all, then try reading directly at the harness(middle wire)....if you have a reading now, then you have a broken wire between the two spots....

Hello Jcat, Thanks again for the help. well the signal wire was working, and the ground is right. The third wire was broke. a shop charged me 2 bucks to fix it because my/ our diagnosis was right. So thank you for that.. the found where it was broke and repaired it. the code is gone. I just got another CEL, I will scan it and find out if it is the sensor or if the wire is broke again. Thank you for all your help!!!

Hello Jcat, Thanks again for the help. well the signal wire was working, and the ground is right. The third wire was broke. a shop charged me 2 bucks to fix it because my/ our diagnosis was right. So thank you for that.. the found where it was broke and repaired it. the code is gone. I just got another CEL, I will scan it and find out if it is the sensor or if the wire is broke again. Thank you for all your help!!! good you found it . broken wires can be most times a PITA........

I was right. It was a different code. So every thing is good now. Thanks for you help!!