CEL help - MAF voltage 16486 - REWARD FOR PROPER DIAGNOSIS

[lookaught]

Dear AZ,

My brother's car (2000 S4) has had the following code for the past few years. It only gets driven about 4,000 miles per year and an indie mechanic had no luck sorting it out (he got to the max dollar amount to exempt the car from emissions). It's driving me insane and I need to fix this.

Anyone who can figure out how to solve this will get a free set of OEM Audi Sport winter S4 mats from my of B5 S4. They are pretty dirty from salt, etc, but shit, they're free! I'll even ship them for free within the continental US. This is just an incentive to get some ideas going and not "STFA" comments.

This is the only code:

Address 01: Engine Labels: 078-907-551-AZA.LBL
Part No: 8D0 907 551 A
Component: 2.7l V6/5VT G 0003
Coding: 06611
Shop #: WSC 01160

1 Fault Found:
16486 - Mass Air Flow Sensor (G70): Signal too Low
P0102 - 35-00 - -
Readiness: 0010 0101


Vacuum leak? We've pressure tested the car several times and found nothing. A new MAF did nothing. Its causing the car to run rich which fouls the plugs every 5,000 miles or so.

Ok guys, I need some ideas, direction, etc. Clearly Im going to try the cheap solutions first before buying parts. I've been out of the S4 game for a few years now but know my way around the car from memory and two turbo swaps in the garage. Thanks for the help!

[mholme]

Sounds like you may have a wiring issue since you swapped MAFS and pressure tested already. Pull the ECU and do a continuity check on the wiring for the sensor. It's in the Bentley I believe.

[A62TURBO]

Did you install a reman. MAF? I wouldn't doubt it being faulty.

[Blue AWD]

Check the connections in the plug that connects to the MAF itself. I had a broken wire in there. Cut open the shrink wrapping and tug on each of the wires individually. MAFs usually fail with signal too high so Im thinking its a wiring issue.

[lookaught]

Sounds like you may have a wiring issue since you swapped MAFS and pressure tested already. Pull the ECU and do a continuity check on the wiring for the sensor. It's in the Bentley I believe.

Do you mean there is a procedure to check the wiring outlined in the Bentley? I need to see if I can even get that Bentley to work anymore, I haven't used it in years. Is it possible for someone to post this?

I honestly don't remember if the MAF was a reman or new. I think it was about $150... it was a few years ago. Im fairly certain that its not the MAF though because I seem to remember swapping the MAF ffrom my old S4 before I sold it and the code still came back.

[2001S4OWNER]

on the 2000 and early 2001 there is a stud on the firewall that rubbs through the wiring harness. there was a technical service bulletin way back. it would cause voltage faults due to short to power or ground. It may not be noticable at first. it was behind the passanger side head. really check to see if the harness is rubbing the stud...break in harness will cause your concern.
I hope that helps

[mholme]

Do you mean there is a procedure to check the wiring outlined in the Bentley?

Yes, it's in the Bentley.

[A4 Meets 27t]

Check this procedure out I hope it helps:

Mass Air Flow Sensor, Checking

NoteUse only gold-plated terminals when servicing terminals in harness connector of Mass Air Flow (MAF) Sensor -G70-.
Special tools and workshop equipment required
- Multimeter.
- Wiring diagram.
- Scan tool

Test requirements

- The Mass Air Flow (MAF) Sensor -G70- fuse OK.
- Battery voltage at least 12.5 volts.
- All electrical consumers such as, lights and rear window defroster, switched off.
- Vehicles with automatic transmission, shift selector lever into position “P” or “N”.
- A/C switched off.
- Ground (GND) connections between engine/transmission/chassis OK.
- Coolant Temperature at least 80° C.
- Ignition switched off.

Function test
– Connect the scan tool.
– Start engine and let it run at idle.
– Using the scan tool, Check the air flow quantity of the Mass Air Flow (MAF) Sensor -G70- at idle:

Diagnostic text Specified value
Air flow quantity at Mass Air Flow (MAF) sensor
l Engine running at idle
2.00 to 5.00 g/sec

– End diagnosis and switch ignition off.

If specified value is obtained, but DTC memory has a DTC concerning Mass Air Flow (MAF) Sensor -G70-:
– Check voltage supply of Mass Air Flow (MAF) Sensor -G70- → Anchor.

If specified value was not obtained:
– Check the Mass Air Flow (MAF) Sensor -G70- electrical circuit → Anchor.

Checking voltage supply

– Disconnect the Mass Air Flow (MAF) Sensor -G70- electrical harness connector -1-.
– Start the engine and let it run at idle.
– Using a multimeter, check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminal 2 to engine Ground (GND).

Specified value: battery voltage.
– Switch the ignition off.

If specified value was not obtained:
– Check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminal 2 to theFuel Pump Relay -J17- terminal 2 for an open circuit.
Specified value: 1.5 Ω max.

If no malfunction is detected in the wiring and if the voltage supply was OK:
Checking electrical circuit

If the manufacturers test box is being used. Perform the following step.
– Install the test box. Refer to

→ Fuel Injection and Ignition; Rep. Gr. 24; Fuel Injection System, Servicing.

If the manufacturers test box is not being used. Perform the following step.
– Remove the Motronic Engine Control Module (ECM) -J220-. Refer to → Chapter.

– Using a multimeter, check the Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminals to the Motronic Engine Control Module (ECM) -J220- electrical harness connector terminals for an open circuit.

Mass Air Flow (MAF) Sensor -G70- electrical harness connector terminals Motronic
1
3
4

Engine Control Module (ECM) -J220- electrical connect or test box socket
1= 53
3= 27
4= 29

Specified value: 1.5 Ω max.

If the specification is not obtained:
– Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).
– Check the electrical harness connector for damage, corrosion, lose or broken terminals.

– If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring and if the voltage supply was OK:
– Replace Mass Air Flow (MAF) Sensor -G70-

→ Fuel Injection and Ignition; Rep. Gr.24; Fuel Injection System, Servicing.

If no malfunction is detected in the wiring and if the voltage supply was not OK:
– Replace the Motronic Engine Control Module (ECM) -J220-. Refer to → Chapter.

Final procedures
After the repair work, the following work steps must be performed in the following sequence:
1 - Check the DTC memory. Refer to → Chapter.
2 - If necessary, erase the DTC memory. Refer to → Chapter.
3 - If the DTC memory was erased, generate readiness code. Refer to → Chapter.
– End of diagnosis.

[Boris]

oh fak, everyone beat me to it.

Well, I would say the same thing, except maybe a little bit more simple.

Since you are 2000, that means someone actually soldered your new maf in, just like I did, and I got the same code at one point.


Check the actual solders to your maf, I think everything before them is probably fine, that harness does not move enough for a problem further down the line to rub open etc.

SO check the actual solders to the new MAF sensor... I bet one of them is real thin or partly broken apart.. THat would cause a low signal., or where the wires plug into the actual socket maybe one is loose, but I bet your problem is right there.

[lookaught]

Great advice so far everyone, I'll get to working on these this weekend.

My memory tells me that the mecahnic said it was a problem with the 5V Pin 4 having intermittent signal or voltage... I'll see if I can get my Bentley running and check all of these wires and harnesses.

[AudiHolicS4]

i know this sounds dumb but i would check the fuse as well i had the same code before and thats what it was from

[mholme]

i know this sounds dumb but i would check the fuse as well i had the same code before and thats what it was from

That's not a bad idea and not dumb at all. Cheap and free if it fixes it.

[ladedruck]

I have fixed two 2.7ts with this code from the main wiring harness coming loose behind the coolant tank and getting melted by the exhaust/turbo. The harness looked ok on the outside but had fused two or three wires together inside.

[MacDaddy]

accordian hose leak

[AudiHolicS4]

That's not a bad idea and not dumb at all. Cheap and free if it fixes it.

yea my car was throwing 16 codes and one of them was that code...i fixed the fuse(fuse 34 BTW) and down to 4 which are from having aftermarket exhaust so the rear o2s always have that code at least until i fix it but thanks for the compliment

[lookaught]

Check the connections in the plug that connects to the MAF itself. I had a broken wire in there. Cut open the shrink wrapping and tug on each of the wires individually. MAFs usually fail with signal too high so Im thinking its a wiring issue.

We have a winner! The wire going to pin #4 was broken at the crimp. My brother and I managed to get the plug apart without completely destroying it and soldered in a 2" wire extension, then soldered the broken wire to it and it works!

It looked fine, but one little tug and the wire came out. First time in three years without a CEL... its amazing! Finally having a MAF input makes the car run immensely better (duh) and damn is Stage 3 fast!

PM me about the mats. I only ask that you don't resell them, so if you dont' need them (ie already have a set) then I'll go down the list until I find someone who does need a set.

Thanks AZ! *high five!*

[mholme]

Glad you fixed it but I really wanted the mats

[Blue AWD]

PM sent! Thanks again and glad I could help.

[lookaught]

PM sent! Thanks again and glad I could help.

PM'd you back. Mats are gone everybody! Thanks to all for the help!

[Blue AWD]

Hey, got the mats from lookaught awhile back. They were in better shape than he had described and was great to work with, thanks again.

[RAyala2.7T]

I'm working on the same exact problem. I narrowed it down to pin #4 and checked voltage. Its only putting out .03v at idle. I rev it and the highest it will go is .06v. I don't have access to a vag com right now so I have to resort to the multimeter.

Question: On the signal wire(the one with the extra shielding), there are two wires inside, green and black. They do stay together when I connect it back to the wiring that leads to the connector, right? S4 wiki states that the signal wire is only a green wire so that throws me off a little bit. All other wires check out and I've narrowed it down to the signal wire. Any help is appreciated guys!

[HIERLEVELZ]

Anyone know where to get the specialty tool to remove the pins from the MAF plug?