18047/P1639 Throttle Fault - Can someone test a known good pedal for me?

srvblues00

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90 ALH 4Rrunner & 99 2500 Cummins TD
Anyone have a manual trans throttle pedal from an ALH TDI laying around? With harness disconnected, can you test the resistance between terminals 1 & 3 at idle and WOT?

I have an 18047/P1639 fault pedal sensor 1 int. signal. MVBs never show anything other than 0.0% for throttle position, but engine will rev to 1200 if pedal is depressed. Each wire to ECM has been load tested with a head light bulb. Connector pins are clean and look good. Appears to either be the pedal assembly or ECM. Neither are likely failures and both are expensive :eek: I think it's the pedal, but I want to be 100% sure.

Resistance between 1 & 3 on my pedal never changes no matter what position its in. This fault doesn't erase and exists whether the pedal is plugged in or not.

So close to getting my 4Runner on the road.. this pedal fault is one of the last major issues to sort out. Most other stuff is pretty minor. I'll post a build thread & pics soon.
 

Rockwell

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mine doesn't change either measured right at the pedal. Are you using the 8" pigtail that connects the pedal to the rest of the harness? The pigtail isn't just an extension, it also changes the wire positions. With the pigtail I get 1.15k ohms at rest, 2.01k at WOT
 
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srvblues00

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90 ALH 4Rrunner & 99 2500 Cummins TD
mine doesn't change either measured right at the pedal. Are you using the 8" pigtail that connects the pedal to the rest of the harness? The pigtail isn't just an extension, it also changes the wire positions. With the pigtail I get 1.15k ohms at rest, 2.01k at WOT
Well, now I am confused. The harness I got was just the engine harness. Nothing body related. So all those 10 pin orange/blue/green/black connectors were just connectors. I've taken the wires out of those connectors as I've needed.

So, I have the throttle pedal, the 6pin pigtail with 8" of wire, and then about 3 feet of 6 wires to the ECM. I just matched terminal 1 of the throttle pedal to the corresponding wire on the diagram. Seems so simple on the diagram - 6 wires all straight to the ECM. The indicated connectors in the harness are not there, therefore I ignored them.

Wish I had another set of eyes to look at this. I'm sure it's something simple, but I just can't see it.
 

srvblues00

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Tonight a customer brought me a 2000 TDI NB to do some work on, so I finally was able to get some test parts :) I swapped pedals.. that's not it. My pedal works in their car. I am confident in my wiring; I have checked it multiple times over several weeks in between other parts of this project.

I have the correct signal on pin 3 of the brake switch (white/yel). The only thing I'm not sure about is pin 4 (red/blk) that goes back to the ECM. It has 12v on it when the brake switch is plugged up. Kinda hard to tell from the diagram what it's supposed to since the other end of the switch connects to power as well (pin 1, I think. Diagram is not in front of me). :confused: But, that red/blk wire size is 1,0, so it's believable that it's supposed to have power on it. Also my clutch switch is connected in the non-depressed state.

In the NB test car, as expected, the throttle percentage still changes no matter the state of the brake switch. My Yota throttle sits at 0.0 no matter what.

I am out of ideas. I think it's time to find another ECM to try. At least I don't have one with the immobilizer.

Any other ideas?
 

AndyBees

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Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
I had a similar issue with my ALH in the '84 Vanagon project.

I had been driving the vehicle for quite some time... actually to the 2012 TDI Fest in Ypsilanti, MI, etc. Then, back in August of this year, without warning no pedal. The engine defaulted to about 945 RPMs at idle and that was it. Luckily, I was able to idle home (about two miles).

Anyway, all the wires showed very close to the same ohms (basically no difference). I tried three different pedals without any change.

Then, I decided to "cut out" the splices near the 6-pin connector. I had twisted and soldered them. Upon re-splicing, I just twisted them and used heat shrink tube.

Presto, it worked.

So, I'm thinking you need to re-visit your wiring!
 

srvblues00

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Jun 8, 2008
Location
Lincolnton, NC
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90 ALH 4Rrunner & 99 2500 Cummins TD
I had a similar issue with my ALH in the '84 Vanagon project.

I had been driving the vehicle for quite some time... actually to the 2012 TDI Fest in Ypsilanti, MI, etc. Then, back in August of this year, without warning no pedal. The engine defaulted to about 945 RPMs at idle and that was it. Luckily, I was able to idle home (about two miles).

Anyway, all the wires showed very close to the same ohms (basically no difference). I tried three different pedals without any change.

Then, I decided to "cut out" the splices near the 6-pin connector. I had twisted and soldered them. Upon re-splicing, I just twisted them and used heat shrink tube.

Presto, it worked.

So, I'm thinking you need to re-visit your wiring!
Yeah you might be on to something. I'm sure whatever it is will be simple.. always is. Only thing is that all my throttle wires will brightly light an H1 headlight bulb, so the circuits will carry some load. I used the 3M heatshrink butt connectors for my splices with a ratcheting crimper that creates a proper and consistent crimp every time. I'll still check it all again tomorrow. Hopefully I'll see something I missed the last few times I've looked at it.
 

AndyBees

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Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
I think maybe the ECU senses a difference in resistance, throws the code and then defaults to limp mode idle.

I worked with mine for almost a week trying to deciper the issue. I felt certain that the circuits were fine. I installed all three of the pedals on my Jetta and they worked fine.

Anyway, as I said, re-splicing those 6 wires solved my problem.
 
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jimbote

Certified Volkswagen Nut
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spiral arm, milky way (aka central NC)
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Tacoma 4x4 converted to TDI
the pedal wiring on the mkiv does some wack changes at the colored connector ... for example one particular wire color does not connect to the exact same color on the other side of the connector !!.... all I'm saying is carefully check your wiring against the diagram ;)
 

srvblues00

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90 ALH 4Rrunner & 99 2500 Cummins TD
Hmm... just noticed something that might make a difference. I realized the T6a connector is NOT the connector at the throttle pedal. T6a originally was originally behind instrument panel, left. The diagram does not specifically label the pin numbers on the throttle pedal itself, just that T6a connector further up the line.... a connector that I don't have. I'll have to go check again... I'm getting cross-eyed!

 

srvblues00

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Can someone take a picture of their throttle pedal connector? My connector must be from a newer 121 pin ALH.. the colors don't match the diagram and the pins aren't labeled in the diagram. :\ Both of my diagrams show solid color wires, but my connector has striped wires.
 

AndyBees

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Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Wire color below: Left side is at the Blue Connector as they come from the accelerator and the right side is at the ECU as they leave the blue connector. Follow the circuit/wire from left to right (accelerator is on right, sort of confusing).

Blue Connector - 10 pin, T10h
 
Pin # ....Wire Color ...............Connection ..To ..........At accelerator
 
1 >br/bl - gn/ro < ECU side ...Pass-thru ....ECU 51 ...Accelerator connector Pin #6

2 >gr/ws - ws/bl < ECU side ....Pass-thru ...ECU 63 ....Accelerator connector Pin #1

3 >ge/gr - ge/gr < ECU side ....Pass-thru ...ECU 12 ....Accelerator connector Pin #2

4 >gr/ro - gr/ro < ECU side ......Pass-thru ...ECU 50 ....Accelerator connector Pin #3

5 >ws/bl - gr/bl < ECU side .......Pass-thru ...ECU 69 ....Accelerator connector Pin #4

6 >gr/bl - gr/ws < ECU side .......Pass-thru ...ECU 70 ....Accelerator connector Pin #5

7 >No use (empty, no wire, etc.)

8 >bl/ge - bl/ge < ECU side .......Pass-thru ....ECU 18 ....Relay 109

9 >No use (empty, no wire, etc.)

10 >No use (empty, no wire, etc.)


Accelerator connector pins on left and blue connector circuits on right. The wire color is the same from the accelerator to the Blue Connector. Some circuit change color on the other side going to the ECU as seen above.

6>--- 10h/1 br/bl
1>--- 10h/2 gr/ws
2>--- 10h/3 ge/gr
3>--- 10h/4 gr/ro
4>--- 10h/5 ws/bl
5>--- 10h/6 gr/bl

I cannot remember for sure, but either the pedal receptor or the plug has the numbers on it. Magnifying glass and bright light really is useful in seeing those small numbers.

This is how my '02 ALH engine is installed in the '84 Vanagon and is based on the Bentley Manual circuit schematics.

I hope this helps!
 

srvblues00

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Thanks very much for the info, effort, and input. My engine and ECM came from a 99 Golf, so I have the older 80 pin version. I have spent a good amount of time today studying the 121 pin diagram just trying to better understand the circuit and purpose of each wire.

Earlier today I completely ignored all wire colors and made sure my 6 pin connector matched the 80 pin diagram below.

I had continuity as follows:
Throttle pin ... ECM Pin
1 .............. 24
2 .............. 11
3 .............. 23
4 .............. 12
5 .............. 8
6 .............. 25


According to the diagram in this thread, the above should work. I can't see why not. That diagram is clear, simple, and easy to read.

The confusion sets in where my diagram says T6a/5 and 6. Is T6a the actual connector on the throttle assembly itself, or as the diagram says, T6a is behind instrument panel, left? In that case, which pin on the pedal is the real 5 and 6? There are numbers on the pedal and pedal connector, which is how I wired it, but how they correspond to the diagram is confusing. That's why I was hoping to find a picture of an 80 pin version of the throttle connector. I could compare colors and at least be certain on pin orientation at the pedal. I tend to over-think things, so I'm probably thinking too deep here. :)

I have 2 versions of the 80 pin ALH diagram. Pins agree between both of them. Setting the circuit up as shown below resulted in a 18047 fault as soon as the pedal was pushed past the idle switch.

To add to the confusion, the 3rd bit for the brake switch in MVB 6 G 3 always stays at 1, so it thinks F is actuated. It's a very simple circuit for F. You have power into the brake switch, and when the pedal is depressed the contacts disconnect, & power is no longer sent to the ECM via pin 20 on a 1,0 red/blk wire. At that time the 3rd bit should change back to a 0. Well, that wire coming out of pin 20 has power on it any time the key is on! So, it appears that my ECM is shorted to power internally on at least pin 20. The other half of the brake switch that is indicated by the middle bit in MVB6G3 works as it should. Hard to say if this is part of my throttle issues. Even if it would limit the fuel, MVB 2 should show a throttle angle percentage. Luckily I can find replacement ECMs for $100ish on ebay. I just don't want to wait a week to see if that fixes any problems.

It's just 6 wires - should not be this hard. All electrical work I've done on this project for the past year has worked 100% the first time I powered up said circuits... until I get to the last piece of the puzzle before a test drive. This is driving me crazy.


 

srvblues00

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90 ALH 4Rrunner & 99 2500 Cummins TD
A 2nd ECM made zero difference. Now I have a spare to send off to get soldered.. meanwhile vehicle will still be operational on 1st ECM.

More digging found that my pedal is part # 1J1 721 503 H which my Google Fu suggests is for an AHF engine. ECS Tuning says I should have 6Q1 721 503 L. Wonder if all this mess is because I need a different pedal? Anyone know for a fact if the ALH and AHF pedals are identical?
 

jimbote

Certified Volkswagen Nut
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spiral arm, milky way (aka central NC)
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Tacoma 4x4 converted to TDI
ok I'm thinking the T6a connector is indeed the connector on the pedal and the solid color wires indicated in the diagram are vestigial from the older A3/B4 wiring as they do have a pigtail with solid wires coming off the TPS and to a 6 pin connector ... hope this helps
 

srvblues00

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90 ALH 4Rrunner & 99 2500 Cummins TD
is your pin 25 ecm brown/blue also grounded ? EDIT:....this will be brown/blue pin 1 of the tps connector
Yes, I have ground on pin 25 at ECM, pin 6 at TPS, and the MAP sensor also shares this ground. One observation that might be over thinking it here == I believe that pin 25 ground is supposed to be a sensor ground plane. My meter readings are the same if I put the ground lead on ping 25 or 6 or a chassis ground. Not sure if that matters - I don't have a working factory TDI car at my disposal right now to test.

jimbote said:
ok I'm thinking the T6a connector is indeed the connector on the pedal and the solid color wires indicated in the diagram are vestigial from the older A3/B4 wiring as they do have a pigtail with solid wires coming off the TPS and to a 6 pin connector ... hope this helps
Yes, I think you are right. After working with this for several more days, I am convinced T6a is in fact the TPS connector. What adds to the confusion is my pigtail was from a 121 pin harness, so the colors are all over the place. I no longer look at wire color - that is irrelevant! I just check what pin on T6a is supposed to connect to what pin on T80 ECM connector. Much easier that way.

I took some voltage readings on my pedal at varying conditions. I'll post that separately.
 

srvblues00

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Here's my voltage readings at the throttle pedal. For all tests the meter negative lead was on pin 6, but readings were the same if negative lead was on a known good chassis ground.

Condition: pedal not plugged into T6a, open connector
Pin 1 - 0.08v
Pin 2 - 4.96v
Pin 3 - 0.01v
Pin 4 - 2.75v
Pin 5 - 8.17v
Pin 6 - neg lead

Condition: pedal plugged in; at idle position
Pin 1 - 0.08v
Pin 2 - 4.94v
Pin 3 - 0.01v
Pin 4 - 0.501v
Pin 5 - 0.15v
Pin 6 - neg lead

Condition: pedal plugged in; at WOT position
Pin 1 - 0.01v
Pin 2 - 0.00v
Pin 3 - 0.01v
Pin 4 - 4.38v
Pin 5 - 8.30v
Pin 6 - neg lead

My pedal is wired as follows:
T6a/1 to ECM 24
T6a/2 to ECM 11
T6a/3 to ECM 23
T6a/4 to ECM 12
T6a/5 to ECM 8
T6a/6 to ECM 25

Even though each wire brightly lights an H1 headlight bulb, I suppose there could possibly be a small resistance issue. Seems unlikely, but I guess anything is possible. Maybe next before buying a pedal with the right part number I should load up each wire again with the H1 bulb and check the voltage drop.
 

srvblues00

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90 ALH 4Rrunner & 99 2500 Cummins TD
I got my hands on a pedal with the correct part number for a 99 manual Golf. Still no throttle angle. Whiskey Tango Foxtrot. I wonder if some other componets would cause this? I will not be using EGR, the anti-shudder flap, and currently do not have the wiring in place for the coolant GPs. There are shared connections in the harness, what about shared connections inside the ECM? I know, hard to say for sure.
 

AndyBees

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Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
None of the things you mentioned should affect the accelerator circuits.

Check all splices relating to the circuits.
 

srvblues00

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Fixed it this afternoon.

A friend and Mercedes tech I went to school with at NTI came over to put a fresh set of eyes on the situation. He was coming up with exactly the same readings, conclusions, etc, that I posted above. He didn't see anything obvious. My wiring matched the VW diagram perfectly. The voltages we had on the pins at the pedal did not make sense according to the pedal diagram on the wiring diagram.

We then removed the circuit board from the older of my 2 pedal assemblies and figured out what each wire was supposed to do. We had 3 of the 6 wires in the correct location based on voltages read and the All Data test plan. After a few tries of switching the other 3 wires around, we found the correct combination. Pedal potentiometer now reads properly and there are no faults. Engine revs like it should and it's a beautiful sound!

The wiring diagram is wrong/highly misleading. Don't analyze the electrical schematics in the pedal assembly on the "from 98" ALH diagrams. In my case, they were wrong. Some ting wong.
 

Rockwell

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That's good news. Can you post your findings?
 

srvblues00

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That's good news. Can you post your findings?
Sure. It'll be a day or two before I have time to get back to work on it, but I'll post info soon. I was already planning on documenting the changes so in the years to come I'll know what we changed vs the factory diagram.
 

AndyBees

Top Post Dawg
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Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
For what it's worth, I have an early 1960s Official VW Repair Manual for the 40 hp air-cool engine. My college geology professor gave it to me over 40 years ago.

Anyway, over in the book, he has a correction marked in the wiring diagram of the four spark-plug wires. They would have you to cross-wire two of the cylinders according to their diagram!

Yep! It can happen!

Glad you found the problem(s) ..... always a good uplifting feeling to whip an electrical gremlin!
 

srvblues00

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Corrected pedal wiring is as follows for the "from 1998" 80 pin ALH engine:

T6a/1 to ECM 8
T6a/2 to ECM 11
T6a/3 to ECM 23
T6a/4 to ECM 24
T6a/5 to ECM 12
T6a/6 to ECM 25
 

jimbote

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spiral arm, milky way (aka central NC)
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just to clarify (or add confusion)....here's the wire colors for the above pinout correction posted by srvblues00....

T6A1 white/blue --- ECM8 grey/white
T6A2 yellow /green-- ECM11 yellow/green
T6A3 grey/red ---- ECM23 grey/red
T6A4 grey/blue----- ECM24 white/blue
T6A5 grey/white----- ECM12 grey/blue
T6A6 brown/blue -------- ECM25 brown/blue ....

the 121 pin ecm does similar color "swapping" at the plenum chamber connector although there are some color differences ...of course if you retain the plenum connector there is no need to worry ;)
 
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Syncrogreg

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Feb 22, 2010
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Hello,

Anybody knows the pinout for that pedal. I'm talking about the +5. Signal and GND. We are using it for a stand alone application
 
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