MAF signal wire only getting 2.7 volts
01-21-2013, 07:35 PM
#1
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MAF signal wire only getting 2.7 volts
I keep getting a p0100 code at start up, i checked the maf, it has good ground, 12v power to the pink wire, but i am only getting 2.7 volts to the yellow signal wire from the pcm.
I checked the yellow wire at the PCM and at the maf connector, same reading.
I also tried several different MAF sensors with the exact same results.
I am at a lose as to what could cause this.
Some info on the car, it has been taken apart and pieced together several times.
It is a obd2 computer and motor from a 97 in a 93 car, so some cutting and splicing has been done inside the car.
However i not sure how any of that could affect the voltage the pcm is putting out.
I checked the yellow wire at the PCM and at the maf connector, same reading.
I also tried several different MAF sensors with the exact same results.
I am at a lose as to what could cause this.
Some info on the car, it has been taken apart and pieced together several times.
It is a obd2 computer and motor from a 97 in a 93 car, so some cutting and splicing has been done inside the car.
However i not sure how any of that could affect the voltage the pcm is putting out.
01-21-2013, 09:27 PM
#2
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Re: MAF signal wire only getting 2.7 volts
You should see 4 to 6V at the PCM connector pin, with the yellow wire disconnected. If you have that, the PCM is good. Then check the voltage at the PCM pin with the yellow harness wire connected, and then at the MAF sensor end of the wire, with the harness not connected to the MAF. Do you have 4-6V? That would prove the wire good. Then connect the harness to the MAF and measure voltage.
Does your multimeter have a frequency setting? With the harness connected, engine idling, probe between the yellow wire and the black/white ground wire and look for about 2,000 - 2,500 Hz. Move the throttle to see if the frequency increases with increasing throttle position.
Low voltage on the yellow wire can be either the PCM, or the yellow wire shorted to ground.
Does your multimeter have a frequency setting? With the harness connected, engine idling, probe between the yellow wire and the black/white ground wire and look for about 2,000 - 2,500 Hz. Move the throttle to see if the frequency increases with increasing throttle position.
Low voltage on the yellow wire can be either the PCM, or the yellow wire shorted to ground.
01-21-2013, 09:37 PM
#3
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Location: Maryland
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Re: MAF signal wire only getting 2.7 volts
You should see 4 to 6V at the PCM connector pin, with the yellow wire disconnected. If you have that, the PCM is good. Then check the voltage at the PCM pin with the yellow harness wire connected, and then at the MAF sensor end of the wire, with the harness not connected to the MAF. Do you have 4-6V? That would prove the wire good. Then connect the harness to the MAF and measure voltage.
Does your multimeter have a frequency setting? With the harness connected, engine idling, probe between the yellow wire and the black/white ground wire and look for about 2,000 - 2,500 Hz. Move the throttle to see if the frequency increases with increasing throttle position.
Low voltage on the yellow wire can be either the PCM, or the yellow wire shorted to ground.
Does your multimeter have a frequency setting? With the harness connected, engine idling, probe between the yellow wire and the black/white ground wire and look for about 2,000 - 2,500 Hz. Move the throttle to see if the frequency increases with increasing throttle position.
Low voltage on the yellow wire can be either the PCM, or the yellow wire shorted to ground.
Thanks for the reply,
I have not checked the actual pin on the pcm yet, just the wire a few inches away from the pcm. only getting 2.7 volts.
Ill figure out how to test frequency.
02-09-2013, 02:58 PM
#4
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Re: MAF signal wire only getting 2.7 volts
so, at the PCM on the yellow wire i am only getting 2.xx volts. So i am guessing that means the PCM is shot (or atleast the part that converts the 12v to 5 v for the pin)
So can i take the 5v A/C ref wire and tap that into the maf yellow wire so that it is supplied with 5 volts?
I done have the A/C installed so it is not doing anything.
So can i take the 5v A/C ref wire and tap that into the maf yellow wire so that it is supplied with 5 volts?
I done have the A/C installed so it is not doing anything.
02-09-2013, 04:10 PM
#5
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Re: MAF signal wire only getting 2.7 volts
Dd you check the frequency on the signal wire with the engine running? The frequency rides on whatever voltage is present. If the PCM is getting a frequency signal, should still work. The key is does the frequency vary with air flow? The code sets when the frequency doesn't vary at least 2 counts between subsequent reads.
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