Rewiring Throttle Body

[LowKeyLoki]

So I’ve been having issues with my throttle over the past few months, keeps throwing various potentiometer and basic setting faults randomly. I replaced the throttle and pedal months ago but issue persisted intermittently. I’ve narrowed it down to the wiring from TB to ECM, I replaced the connector to the TB and spliced new wires/terminal ends which came with the kit but not being advanced in wiring I didn’t realize that the new wires to the TB were slightly differ gauge and were all copper vs aluminum OFC factory wiring. So I’ve still been having intermittent codes for the sensor 2 potentiometer in the TB.
Question is can I snake new wires through the engine harness to the ECM easily? I was thinking of using coat hanger or fish tape to snake them through, or crimping new wires to old and snake them through that way.

Also should I buy new OEM repair wire and crimp on my own terminal ends or should I buy a entire engine harness for $140 and just take the original wires out of that and able them through the harness?
Trouble I’ve been having is finding the exact terminal end crimp from TE connectors.

Anybody have experience re routing wires or any advice as to how to figure out the correct terminal crimps?
Crimp at TB is different from crimp terminals at ECU fyi.

[Fresh.S4]

ive mixed wire types before and never had a problem, as long as they are connected properly.

i dont know about snaking wires through the loom...
have you tried a different throttle body?

[LowKeyLoki]

I used proper gauge heat shrink butt connectors, twisted wire before crimping and used a proper crimp tool. Issue went away for two weeks about but has returned throwing TB codes. From what I’ve read, since they are signals wires they have very low tolerance when it comes to resistance and wire length/gauge. I bought a used one first, and then ended up buying a new one from FCP. I’m out of town but this weekend I’ll swap the TB out with the old one see if it makes any difference, but I’m fairly certain the issue lies with the potentiometer wires for the TB.

[jessenepywoda]

Use the same exact wire in size and metal content. You want the twist to be continuous, stagger the splices, and the wires must be the same overall length when you're finished. I ordered terminals from multiple places and never found the quality of the OE ones - getting the used harness might be a good move.

[LowKeyLoki]

Thanks man yeah I went ahead and ordered the harness the other day, seems to be the cheaper and more reliable option vs dealership repair wire and searching for correct terminal ends. I also realized that the heat shrink butt connectors were probably slightly oversized, I used the red 22-18 gauge connectors when really the original wire is 24 gauge, but the harness repair kit used 22 gauge wire (DOH!). Will update once I re wire everything.

[JRYtheS4]

It isn't going to be as sensitive as you think.. get a multimeter and check the resistance end to end. It's either going to be a good connection or it isn't. The only thing with using dissimilar metals will be corrosion so stick with using copper with copper and aluminum with aluminum. Using a 22g wire in place of a 24g wire will not have any effect on the tb signal.

Sent from my SM-G991U1 using Audizine Forum mobile app

[Smac770]

The throttle body has 6 pins and houses one motor and two angle sensors:

G186 throttle plate motor
pin 3 - power/ground
pin 5 - power/ground
move the plate by applying voltage to whichever side

G187 throttle plate angle sensor 1
G188 throttle plate angle sensor 2

1 - G187 angle sensor 1 analog output voltage
2 - G187/G188 12v
4 - G188 angle sensor 2 analog output voltage
6 - G187/G188 ground

The G187 and G188 are inverted, so the two voltage measurements together should add up to the source voltage (12v). G187 should increase with angle, G188 should decrease with angle. I presume the ECM does a subtraction of the two signals to eliminate noise pickup.

Part of the question would be is your error out of range readings, or no readings at all. If the error is specific to the G188 value, then you're looking at the G188 potentiometer internally or the white/yellow wire to ECM T60 pin 13. Routes direct from the TB through the harness bundle to the ECM. Not sure how you could snake a new wire through that bundling without cutting it open and resealing it. What did a voltage drop resistance measurement yield for pin 1 to T60 pin 28 vs pin 4 to T60 pin 13? Did one or the other show excessive resistance.

You found a 8K1 971 072 CE for $150, that's really good. It's over $1500 new. The plug for the harness to the TB is 4H0 973 713. https://www.shopdap.com/4h0-973-713.html

[LowKeyLoki]

Ive gotten intermittent codes for both throttle body and SC regulator flap. For the Tb i've gotten both codes P0121 and P0221 for Throttle/Pedal position sensor switch A and B performance and usually will throw P1559 Throttle malfunction basic settings as well. When I was originally having trouble I tested the voltage and resistance from all pins at TB and SC flap back to ECM and couldnt find any with greater than 0.1 ohm.

The 5V pins were all approximately 4.3 or greater if i remember correctly, which in the manual it says approx 5V so idk, i assumed that was within spec? I had the ECU bench tested professionally just to rule it out ($80 not to bad imo). Since the codes were popping for both SC and TB I suspected the common ground terminal pin on either the TB or SC. I ended up splicing new wires (which came as a harness kit with non OEM wires) to all 6 pins at TB and just spliced the #3 pin on the SC regulator flap (again with non OEM wire from a ebay harness kit). This seemed to solve my problems for all of two weeks before I started getting TB errors for potentiometer etc.
Nothing looks out of range when looking at live data on VCDS for throttle valve potentiometer or for pedal position sensor/potentiometers. I have three TB now and all have had issues so I hope I can safely rule out that being the root cause (one original, another used, and a new one from FCP)

I have the used harness now but I am going to pin test the harness on TB and SC flap again and will report back the values.
And yes the harness was a good deal consider the outrageous cost for repair wires from Audi/VW.

[LowKeyLoki]

UPDATE: SOLVED
So after splicing the TB and SC flap wiring harnesses from a used engine harness I bought, I respliced all the wires with proper 24-26 gauge insulated butt connectors (vs the 18-22 gauge ones I had used with the non-OEM wiring harness I bought on ebay), and used proper crimping tool and kept wires as close as I could to the original length. After several days of hwy/city driving I have yet to pop and codes for TB or SC. I did not pin test everything again as I was certain 99% the issue was with the wiring. (Sorry didnt take more pics might update later)
Moral take away: always use proper OEM wires or dealer repair wire fro your repairs, and make sure to use the proper sized butt connectors.

Also, decided to go ahead and swap out my SC intercoolers, had a new Mahle pair from FCP sitting for months in a box, and BOY I am glad I did.
Both looked like shit, pics below are only from one bank but both looked the same. This one the main gasket was cracked or cracked right when I pulled it out as you can see.
I know I had a small coolant leak as I was losing very small amount overtime and was fairly certain it was one or both intercoolers, as I had just done my PCV, water pump, Tstat, etc 8 months ago.

For future people performing this DIY I'd def recommend replacing the bolts holding the Intercoolers, manual says to do so but I forgot to order them and was already into the job so meh. I did clean out the thread holes with a tap which factory manual says to do, and cleaned the bolts best I could with wire brush. Taking them out was easy, light tapping with wooden board and mallet flat against front of IC's. Install little more difficult, main thing is lube with engine oil the main IC black gasket running its length and slowly slide them in, once they dont move easy by hand I gently tapped them in with a rubber mallet making sure the separate front o-ring doesnt start rolling its lip. Once its in almost all the way you can thread a couple bolts to hold the white gasket in place.

These were the originals on an engine with only 59K miles (stage 1 for only 5k), with how bad they are I def consider them a preventive maintenance item and should prob be replaced every 50-60k mile.
After replacing both I have noticed my idle is much smoother than before, I'm sure small drops were leaking into one of the cylinders causing slight hiccups.


IMG_4731.jpgIMG_4735.jpgIMG_4775.jpg

[Fresh.S4]

soak those bricks in simple green or a very mild dawn soapy water and use a tooth brush and clean all the residue off.

now you've got yourself an emergency set of bricks!

[LowKeyLoki]

Nah man they are Toast, even if I could clean them up the main gasket isn’t a part they sell separate nor would I risk putting already leaky coolers in my engine. They are just scrap metal at this point.

[Fresh.S4]

i didnt catch the long gasket was blown out.