When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I've recently been having problems with my MAF sensor. I am consistently getting the P0102 code (as pending and as a trouble code after the 2nd start up some times after a short drive).
I purchased a new one and the problems remained. So I got out the volt meter and checked the wires.
One wire which I assume is the voltage is getting around 12 volts (maybe a little more or less, I used a cheap meter).
The wire on the opposite side is putting out 2.95 volts (or so)
The middle which I assume is the ground has a complete connection when using the OHM meter.
Is it safe to assume I may have received a bad maf and both are bad?
If the volt meter is cheap then I am guessing the ohm meter will be too and will not have the resolution to give an accurate reading to the extent that you need it. The earth lead will be the black lead; use your volt meter and measure the voltage. If it is zero then most likely your ground is fine. If you see a voltage then you have resistance on your earth part of the circuit which will probably be your problem. I.E something is loose or damaged somewhere between your sensor and the circuits earth point.
The other wire. Most auto circuits are parallel, i.e power in and earth out so I am wondering what this other wire is. If it is reading 2.95v then your sensor is not getting 12v which in itself may be your problem. Then again I am not an expert on sensors and do not know what they require. I will try to dig out the wiring diagram tomorrow.
Before measuring the earth lead check the power lead again to ensure you have 12v otherwise the earth wire will read 0v!
Last edited by yellowshark454; Jul 19, 2015 at 06:18 PM.
Reason: clarification
Sorry 1998, A4. Ram air fuel rails fuel pressure regulator.
It is getting 12 volts. The ground is definitely good, the connection is clearly complete between the ground wire and the frame.
The sensor wire is around 2.95 I thought it was suppose to be 5 volts. I also read that you need to have a good MAF attached to it for you to get 5 volts.
I've been searching the internet for maybe a combined 3 hours and can't find one wiring diagram.
Last edited by robert1989; Jul 19, 2015 at 10:46 PM.
I'm fairly sure you should be getting 5 volts + even without the MAF sensor connected.
I'm going through the same thing (you probably saw my posts ) For me I think I traced it down to the ECU itself. Waiting for a replacement to come in...
Hi Robert you say the ground is clearly complete, are you doing a continuity check? This will only tell you that the wire is connected to ground, you need a voltage check to establish any significant resistance
I'm fairly sure you should be getting 5 volts + even without the MAF sensor connected.
I'm going through the same thing (you probably saw my posts ) For me I think I traced it down to the ECU itself. Waiting for a replacement to come in...
There is some information I am leaving out.
The voltage check was done using the ground on the MAF and the frame both show voltage on the power side.
As for getting 2.95 volts or so on the sensor wire. Now, I'm not an electrical engineer but I'm going to go out on a limb here and say that that wire is an input wire. So the MAF gets a ground and a power wire. Which are both working fine but I assume that it needs to send the information back to the ECM (or what ever). To do this the MAF sensor increases or decreases voltage on that sensor wire within what ever range. Telling the ECM what it is getting.
Since it is in closed loop the ECM is going to use a default voltage reading for it's closed loop. I assume the ECM is going to set that voltage to what ever the closed loop input is.
Did you read the link provided? That's not how the MAF sensor works (detecting the voltage drop). Instead, it measures the frequency. It has very specific step by step test procedures.
I replaced my MAF sensor also thinking something was wrong with it but it didn't fix the problem at all. It wasn't until I followed the procedures in the link (same as the factory service manual) that I accessed the PCM in the wheel well and found it caked in salt
The yellow signal wire should measure 5V with the connector unplugged from the MAF sensor. Once connected, it becomes a frequency output and you would need a meter that measures frequency or an oscilloscope to properly measure it.
You MUST measure between the pink power and black ground wires with the MAF sensor connected or another load like a light bulb. Something like a 55W headlight bulb would good since it'd put a decent load on the circuit.
With the load as above, you can also measure from the battery positive terminal to the pink wire and the battery negative to the black wire to see how much voltage drop each circuit has. This becomes somewhat subjective because every circuit has voltage drop so you have to determine if what you measure is normal or abnormal.
I'm fairly sure you should be getting 5 volts + even without the MAF sensor connected.
I'm going through the same thing (you probably saw my posts ) For me I think I traced it down to the ECU itself. Waiting for a replacement to come in...
I didn't see your issue. Are you still getting voltage and was it your ecu?
I got like 1/2 a volt with the old ECU. The new one just came in today, in fact I just put it in and am performing the BCM relearn right now, but otherwise when I put the new computer in, it read 5 volts at the yellow wire with the MAF sensor disconnected, with the IGN to on
Holy crap, I've changed my battery quite often. I doubt mine looks like that.
I'm starting to believe it is the pcm though. Where did you get yours and how much was it.
I found someone who said they can definitely repair mine and it will cost 151 dollars.
I also found someone who said they will sell me one for less than $100 for a 99 car (Apparently the pcm is used in several different cars) but I will have to repin it to 99 corvette pinning (comes with vin flashed onto pcm).
The 99 would be a good upgrade but would take me about 2 hours to conduct (round about).
Edit: I'm also stuck in VA until next week. So I wont be doing any messing with it. It has to be able to take me home.
I got mine used from a fellow forum member. Have to get it reflashed as it was out of an auto and mine is a manual so it's throwing auto trans sensor codes. I thought about the repin and 411 conversion too but that's a whole other can of worms. Just do a quick search and people having conversion troubles was enough to turn me off. Unless you are planning on extensively modifying the cart i wouldn't recommend it.
Originally Posted by robert19890412
Holy crap, I've changed my battery quite often. I doubt mine looks like that.
I'm starting to believe it is the pcm though. Where did you get yours and how much was it.
I found someone who said they can definitely repair mine and it will cost 151 dollars.
I also found someone who said they will sell me one for less than $100 for a 99 car (Apparently the pcm is used in several different cars) but I will have to repin it to 99 corvette pinning (comes with vin flashed onto pcm).
The 99 would be a good upgrade but would take me about 2 hours to conduct (round about).
Edit: I'm also stuck in VA until next week. So I wont be doing any messing with it. It has to be able to take me home.
MAF sensor voltage
) For me I think I traced it down to the ECU itself. Waiting for a replacement to come in...
