MAF wiring melted. Now no signal

[Furly]

Long story short, I installed an HPx MAF and using the provided pigtail made wiring and crimped it to the OEM maf wiring harness. Car ran great until my wire got loose and fell onto the cat. This melted all the wires and made them touch eachother bare. I lost MAF signal when doing tuning and figured I fried the maf. Got a brand new replacement sensor and pigtail and made new wiring and crimped it all the same way, fired the Car up and still no MAF signal. Traction light is on. Checked fuses and they're fine minus the cig lighter (front electrical poet) popped the ECU open and inspected for burn marks or melted solder and all looks fine. Anyone have any idea what is going on? Anything else I should check ? Need to button this up asap and finish tuning so the car can go off to the body shop. Thanks!!

[old guy]

First determine if you are getting the proper signals to the MAF sensor. This will help figure out what's missing.

Unplug the MAF sensor. Crank the engine briefly and check terminal 2 to ground. You should see battery voltage. Next briefly crank with the multimeter checking voltage between terminals 2 and 3. You should again see battery voltage. Terminal 3 is the ground. Then check between terminals 3 and 4. You should see 5v.

[a4darkness]

Bumping for more eyes on this.
Exact same thing happened to me with the MAF harness wiring, however after splicing in a different plug + wires from a donor harness everything worked just fine.

First determine if you are getting the proper signals to the MAF sensor...

Fletcher it's been a while, hope you are well my friend. ;-) Congrats on the A5!

For some reason Furly thinks I know electrical well enough to help solve this issue. However what you've posted is a above my pay grade.
You mind giving us a bit more detail as to how to perform this testing? TIA

[old guy]

Hi Thomas! Good to hear from you. I'm enjoying the A5 but to be honest, the A4 is still more entertaining.

The testing is pretty straight forward. All it requires is a multimeter to read a voltage signal. When you unplug the MAF harness you will notice that there are five terminals inside the plug and the plug has a flat end and a round end. Terminal one is on the round end and terminal 5 is on the flat end.

Set the meter to volts and put the + probe in terminal two. The touch the - probe to anywhere on the block to create a ground. Briefly Crank the engine and watch the meter for a 12v signal. If you see 12v you will have confirmed proper power to the sensor heater.

Next, leave the + probe in terminal two and put the - probe in terminal three. Briefly crank the engine and watch the meter for a 12v signal. Terminal three is a ground wire. You have already confirmed that terminal two has the required 12v and now you are confirming that the harness also has a proper ground through terminal three.

The last step is to check the actual sensor voltage signal. Put the + probe in terminal four and the - probe in the ground terminal three. You should see a 5 volt signal.

If all this checks out it would indicate that the problem is with the MAF sensor itself. If you don't get the 12 volt heater signal or the 5 volt sensor signal the problem is either in the wiring between the ECU and harness plug or the ECU itself.

[a4darkness]

Great to hear the B6 is still holding up and keeping your interest. Such a great platform.

Okay, this is excellent detail and exactly what we needed. Will do some testing tonight and report back!

[Furly]

Hi Thomas! Good to hear from you. I'm enjoying the A5 but to be honest, the A4 is still more entertaining.

The testing is pretty straight forward. All it requires is a multimeter to read a voltage signal. When you unplug the MAF harness you will notice that there are five terminals inside the plug and the plug has a flat end and a round end. Terminal one is on the round end and terminal 5 is on the flat end.

Set the meter to volts and put the + probe in terminal two. The touch the - probe to anywhere on the block to create a ground. Briefly Crank the engine and watch the meter for a 12v signal. If you see 12v you will have confirmed proper power to the sensor heater.

Next, leave the + probe in terminal two and put the - probe in terminal three. Briefly crank the engine and watch the meter for a 12v signal. Terminal three is a ground wire. You have already confirmed that terminal two has the required 12v and now you are confirming that the harness also has a proper ground through terminal three.

The last step is to check the actual sensor voltage signal. Put the + probe in terminal four and the - probe in the ground terminal three. You should see a 5 volt signal.

If all this checks out it would indicate that the problem is with the MAF sensor itself. If you don't get the 12 volt heater signal or the 5 volt sensor signal the problem is either in the wiring between the ECU and harness plug or the ECU itself.

Hey fletcher. Did the first two steps using the pmas hpx diagram . The hpx sensor doesn't use the 5v #4 on the Audi harness. Do you know what else I can check on the sensor to see if it's getting signal ? I tried using the maf signal the hpx uses and the ground and I get no reading at all. First two steps I'm seeing 11.5v on meter

[old guy]

Can you take a pic or make a quick sketch of the hpx wiring diagram? It uses a 5v signal but maybe it connects in a different sequence than the Bosch MAF.

[Furly]

Can you take a pic or make a quick sketch of the hpx wiring diagram? It uses a 5v signal but maybe it connects in a different sequence than the Bosch MAF.

here's what i used to wire it.

the HPX pigtail diagram:


the audi TT diagram:


basically the HPX uses only 3 of audi's MAF wires.

the power, the two grounds are connected together and crimped into the ground of the car's harness ground on the MAF wiring, and the signal which goes to the "MAF OUT" part. i tested the MAF OUT on the cars harness through the HPX pigtail and got nothing.

[old guy]

Once the engine is warm check the MAF out signal. Here's a cut and paste on how to perform the output test:

Start the engine and let it reach it's normal operating temperature. You'll be using the voltage reading you will obtain at idle as a base to diagnose the MAF sensor.

The MAF sensor must be connected to its connector to perform this test.

With the key in the OFF position.

With a suitable tool connected to the RED multimeter lead, probe the 5 circuit of the MAF sensor connector.

Put the multimeter in VOLTS DC mode.
Connect the BLACK lead to the battery (-) negative terminal.
Start the already warmed up engine.

Note the Volts reading on your multimeter at idle. This reading may be stable (with only small fluctuations) or unstable with very extreme fluctuations. No matter what the instability in the reading, this will be your base reading.

Accelerate the engine as you watch the multimeter's voltage readings.
The voltage numbers should correspond to the amount of acceleration.

Repeat this as often as you need to verify that the voltage numbers on the multimeter rise smoothly every single time.
If the MAF sensor is good, these readings will not spike up and down crazily but will correspond to the amount of air the engine is breathing at the different RPM's you're accelerating the engine to.

Did the signal rise smoothly with each increase in engine acceleration and stay steady at idle?

CASE 1: Your multimeter registered the indicated voltages This confirms that the MAF Sensor is functioning correctly and not the cause of the issue.

CASE 2: Your multimeter DID NOT register the indicated voltages Recheck all of your connections and repeat the test. If still your multimeter does not register the indicated voltages, then the MAF sensor is BAD. Replace the MAF sensor.

[Furly]

Once the engine is warm check the MAF out signal. Here's a cut and paste on how to perform the output test:

Start the engine and let it reach it's normal operating temperature. You'll be using the voltage reading you will obtain at idle as a base to diagnose the MAF sensor.

The MAF sensor must be connected to its connector to perform this test.

With the key in the OFF position.

With a suitable tool connected to the RED multimeter lead, probe the 5 circuit of the MAF sensor connector.

Put the multimeter in VOLTS DC mode.
Connect the BLACK lead to the battery (-) negative terminal.
Start the already warmed up engine.

Note the Volts reading on your multimeter at idle. This reading may be stable (with only small fluctuations) or unstable with very extreme fluctuations. No matter what the instability in the reading, this will be your base reading.

Accelerate the engine as you watch the multimeter's voltage readings.
The voltage numbers should correspond to the amount of acceleration.

Repeat this as often as you need to verify that the voltage numbers on the multimeter rise smoothly every single time.
If the MAF sensor is good, these readings will not spike up and down crazily but will correspond to the amount of air the engine is breathing at the different RPM's you're accelerating the engine to.

Did the signal rise smoothly with each increase in engine acceleration and stay steady at idle?

CASE 1: Your multimeter registered the indicated voltages This confirms that the MAF Sensor is functioning correctly and not the cause of the issue.

CASE 2: Your multimeter DID NOT register the indicated voltages Recheck all of your connections and repeat the test. If still your multimeter does not register the indicated voltages, then the MAF sensor is BAD. Replace the MAF sensor.

Connected the red probe to the green #5 wire and black to battery negative and got a .63 read. Had a friend slowly give it some gas and it climbed .73 .8 .9 1.0 etc..

This is so odd. So I have a maf signal and power and ground both around 11.5v I wonder why my maf is not getting a reading when I'm running logs

[old guy]

Damnation! That doesn't make any sense. Let me give this some thought and see if I can come up with any other suggestions.

[KHARDa4]

Heres how to wire up the HPX-E.
Hope this helps.

Sent from my SM-G955U using Tapatalk

[KHARDa4]

Forgot to add this.

Sent from my SM-G955U using Tapatalk

[Furly]

Heres how to wire up the HPX-E.
Hope this helps.

Sent from my SM-G955U using Tapatalk

This is how I have it wired. It's not making sense to me. It worked before the wires melted and touched bare. Now with all new wiring and sensor it's not working. I even re flashed my ECU to see if that would help

[Kevin C]

Do you have a spare ECU to try? The chip on the ECU may have gotten damaged.

[KHARDa4]

Then you damaged the ECM when those wires melted.

[Furly]

i'll order a used ECU, i'm guessing thats the issue here.

[rovert6]

I’m having this exact same issue. Tried wiring the hpx any which way, but not getting a reading through vagcom. Did you have an issue with your ECU, or what? I can’t seem to figure this out!

[KHARDa4]

Any which way? That can't be good. If you wired it wrong and tried to start the car, it could have certainly fried the ECM. If you hooked up the MAF correctly using the pic i posted above it will work, I used this on my big turbo setup. It only takes one wrong rewire and key cycle to fry that ECM.

Sent from my SM-G955U using Tapatalk

[KHARDa4]

Check for 12V at the connector. That is hardwired to the ECM, if you don't have power there. No bueno.

Sent from my SM-G955U using Tapatalk

[rovert6]

Check for 12V at the connector. That is hardwired to the ECM, if you don't have power there. No bueno.

Sent from my SM-G955U using Tapatalk

I have followed 2 different wiring diagrams. One says to only connect the black ground to the green/black ground for the hitachi. Then another one says to connect the brown and the black wires to the ground. I have tried those and no luck.

I also had Blake Beadle flash another ECU, and still not getting signal to the ECU. I have verified I’m getting 12v to the wire, verified I’m getting a good ground, and my signal wire from the MAF is putting out .13v at idle. I don’t know if the reading should be higher or not at idle though. I’m honestly stumped. No blown fuses, and only have one code for my cel which is the maf.

[rovert6]

I have followed 2 different wiring diagrams. One says to only connect the black ground to the green/black ground for the hitachi. Then another one says to connect the brown and the black wires to the ground. I have tried those and no luck.

I also had Blake Beadle flash another ECU, and still not getting signal to the ECU. I have verified I’m getting 12v to the wire, verified I’m getting a good ground, and my signal wire from the MAF is putting out .13v at idle. I don’t know if the reading should be higher or not at idle though. I’m honestly stumped. No blown fuses, and only have one code for my cel which is the maf.

When I bought the sensor, this is what was sent to me for the wiring diagram. Followed this exactly, crimped it all together, and still had fault codes pertaining to the maf when I finished my 2.7t swap into my B6 A4


Sent from my iPhone using Tapatalk

[Oliver a4 b7]

Hi im new here. Iv owned my a4 b7 2.0tdi for almost 3 years now. 2 weeks ago i melted my maf loom along with a few wires on the other section of the same loom that goes to the egr. Iv repaired all the wires but still not working. I see you had this same issue. Did you ever sort this? Im at a total loss as to what it is at this point. Seen 1 other person had this issue in 2014 but also never said how or if they resolved it. Thanks

Long story short, I installed an HPx MAF and using the provided pigtail made wiring and crimped it to the OEM maf wiring harness. Car ran great until my wire got loose and fell onto the cat. This melted all the wires and made them touch eachother bare. I lost MAF signal when doing tuning and figured I fried the maf. Got a brand new replacement sensor and pigtail and made new wiring and crimped it all the same way, fired the Car up and still no MAF signal. Traction light is on. Checked fuses and they're fine minus the cig lighter (front electrical poet) popped the ECU open and inspected for burn marks or melted solder and all looks fine. Anyone have any idea what is going on? Anything else I should check ? Need to button this up asap and finish tuning so the car can go off to the body shop. Thanks!!