2007 4.2L FSI w/ rough idle P0102 P010C Low MAF

OK so we ordered the driver's side fuel pump (N402). We didnt get an original part, but a Hitachi. It comes with a 1 YR warranty, and for $260 from a reputable place. If it works for 1 YR I will be satisfied lol.

ANyways, so I was able to use a dremel tool to grind a slot into each of the last two safety screws on the clamp over the ecu & ecu connectors locking them together. I got the connector off, and found a diagram that shows which pin is what on the ecu. The wire that is brown with a black stripe leading off the two-pin connector on the N402 does in fact lead to pin 35 on the T60 connector. Here is the diagram I used. Keep in mind the diagram is showing which pin is what ON THE ECU. So you need to mirror it to find the correct pin ON THE CONNECTOR. Just a note for those who may read this and not know.



I used my multimeter to test the continuity and got a nice (beep) to confirm the is at least some continuity.

Then, I tested the resistance, and got numbers varying from 0.1-1.0 Ohm..I have to go to work right now, so after work I will have torun the test again to verify those numbers are correct. I used a resistance calculator and it said even with 15 feet of 15 gauge wire the resistance should only be about 0.06 Ohm. Is that right? Isnt 0.1-1.0 Ohm too much?

If the numbers are the same I will just have to de-pin pin 35 on t60, and the matching pin on the N402 chassis side connector, and run an overlay. I need to get this thing on the road.

I ordered a 21 piece set of tools used for de-pinning connectors. Hopefully what I need is in there.

I still need to test the other wires that relate to sensors/codes thrown after I figured out that fuse S13 was blown. There could be a chaffed wire or cut wire or something. I will start with the G62 engine coolant temperature sensor that was throwing a code indicating a short to positive. I suppose that would explain some things.

Anyways, just wanted to update that

OK so I got some free time to do a little bit of testing and follow me: Here is the diagram of the stuff I tested:



From N402 to T60/35 (brown w/ black stripe) = 0.6Ω
From N80 to T94/9 (lilac w/ yellow stripe) = 0.7Ω
From N290 to T60/60 (brown w/ blue stripe) = 1.4Ω

I wanted to test the N320 & N112 but my time is limited and I have to go to work already.

Those numbers seems high to me, and I wonder what could cause this? cut wiring harness where they all meet somewhere?

Bad ground inside the ecu?

I need to check that G62 ECT sensor and see what the resistance is on that. (The one that threw a code saying short to positive)

Okay today before work I was able to locate the diagram showing G62 engine coolant temperature sensor and do a little bit of testing.



The wire going from G62 to T60/10 has a resistance of 0.1 to 0.4 ohm

The wire from G62 to T60/14 had a resistance of 0.1 to 0.2 ohm

Neither of these showed any continuity to ground or positive.

It is noteworthy that I am becoming of the opinion that any resistance that I am saying is mainly due to the probes and the paperclip Etc that I'm using to get into the pins of the connectors since my probes do not fit..they are too large

I need to get a new set of probes with tips that actually fit down into the connectors!

Also, I retested the wire coming from N402 to T60/35 being more careful with how good of contact my probes were making and the highest resistance reading I got was 0.1 ohm

I need to be more accurate and take that variable out of the equation! Although..it could be moving the wires of the harness contributed. Next time i will flex some wires while checking the resistance.

On a side note...the new N402 High Pressure Fuel Pump comes in vis UPS today! Along with a new o-ring for it and a set of connector terminal tools to de-pin the connectors!

Also, ordered my Hex-Net V2 Enthusiast last night and had it shipped via 2 Day FedEx!

I am pretty excited!

stone4779 said:

It is noteworthy that I am becoming of the opinion that any resistance that I am saying is mainly due to the probes and the paperclip Etc that I'm using to get into the pins of the connectors since my probes do not fit..they are too large

Click to expand...

Any measurement under 1 ohm is subject to substantial error unless you're using a 4-wire "milliohm meter", but those are expensive.

A good alternative is to load-test the wire.

-Uwe-

Uwe said:

Any measurement under 1 ohm is subject to substantial error unless you're using a 4-wire "milliohm meter", but those are expensive.

A good alternative is to load-test the wire.

-Uwe-

Click to expand...

Okay thanks for that tidbit. That's what I was thinking since I was getting pretty consistently at least some resistance measurements in the Tenths of an ohm.

I did purchase two test lights..one for 6/12 volt systems and another one for 24 / 36/48 volt systems. Not sure what the wattage is but I think I might just go to the auto parts store and buy a 55w headlight bulb to load test the circuit with.

At 12 volts and 55w is that too much for that 16 gauge wire going to N402?

As always, thank you for your reply UWE

stone4779 said:

Okay thanks for that tidbit. That's what I was thinking since I was getting pretty consistently at least some resistance measurements in the Tenths of an ohm.

I did purchase two test lights..one for 6/12 volt systems and another one for 24 / 36/48 volt systems. Not sure what the wattage is but I think I might just go to the auto parts store and buy a 55w headlight bulb to load test the circuit with.

At 12 volts and 55w is that too much for that 16 gauge wire going to N402?

As always, thank you for your reply UWE

Click to expand...

55W @12 V = ~4.5A, which should be fine for a 16 gauge wire.

I would buy a smaller bulb for smaller wires though. Something like 10-12W would be ideal to draw around 1A. And bare bulbs are a PITA, so get bulbs with sockets.

-Uwe-

Diagram shows a 1.5 mm conductor, a chart I found showing maximum power load recommended is around 5 amps and for "chassis wiring" (whatever that means?) it is higher..more like 28 amps

Just posting some math for those that may read later

Uwe said:

55W @12 V = ~4.5A, which should be fine for a 16 gauge wire.

I would buy a smaller bulb for smaller wires though. Something like 10-12W would be ideal to draw around 1A. And bare bulbs are a PITA, so get bulbs with sockets.

-Uwe-

Click to expand...

Awesome! Glad to hear it! I did pick up a 55W 9006 bulb with connector.

The new pump has 1.6 ohm resistance across the two pins

For anyone curious...

Well good news fellas!





The brown/black wire from T60/35 to the N402 can carry enough current to light that 55w 9006 bulb.

I am not sure how to check the other (positive) side of the N402? It shows it goes to D116 Connection 14...I need to do some digging in the diagrams.

For now I can at least check the ground wires from the T60 & T94 ECU connectors to things like N80, N290, N320 & N112 (shown in the same diagram as N402 and using thr same power supply circuit)

The new fuel pump looks aweful nice

I also inspected the fuel pump cam roller follower...rolls smooth and normal wear.

And so far....the engine and trans run MUCH better! It doesnt fall on it's face at medium throttle to wide open throttle.

The terrible shake at idle is no longer present...

We took it out to run errands in it for about 2 hours, and it *almost drives perfect now. I think the transmission still could use the SK09D Trans Go shift kit that we should receive next week. Sometimes after a quick decel it seems as if there is a delay on downshifts. I still need to drive it more, and Monday when my Hex-net v2 comes in..do a full scan to see what it tells me.

But overall, id say the car is about 99% engine wise..and about 90% of the way there on the transmission. I have a brand new fluid transfer pump I can use to fill the trans properly after installing the shift kit etc.

Now that I have gotten to give the 4.2L some heavy right foot action, I am very happy with the performance. I cant wait to mod it a little, and to learn more about VCDS.

FYI...all the electric gremlins were ultimately because a short to ground inside the ECU.

Cloned the ECU onto a donor..and...

(Copy from another forum)

"Good news fellas!

I was able to back up the donor tune, then back up the original ECM's tune, then copy over the origin tune onto the donor ECU.

No more DTCs for short to ground, and the two MAFs appear to be actually working for the first time since we got the car in 2020(?) 2019(?)..

It also seems to have resolved various other issues like the rear trunk not automatically closing and fully latching, trans harsh downshifts, jerky throttle response, erratic idle, popping fuse S13 instantly upon starting(main issue), trans shift indicator not working, hard starts, and probably more stuff I haven't checked yet.

I'm super happy right now "