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TDI Conversions Discussions on converting non TDIs into TDIS. More general items can be answered better in other sections. This is ideal for issues that don't have an overlap and are very special to swaping engines.

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Old September 2nd, 2017, 04:36   #1
Tacoma_TDI
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Default ALH Wiring Harness - Necessary Hardware

I'm looking to start a discussion to compile a definitive list of what is needed to create/modify the ALH harness to create a "standalone" setup for those doing TDI swaps, as well as have some questions answered that I'm sure others will come across in the future. The only definitive list of sensors/plugs I've been able to find to date is from Fast Forward Automotive, but I'm wanting to confirm this with other members. So, here we go (slight variation from FFA):

1. ECU
2. +12V Battery
3. Glow Plug Relays
- High Heat Output Relay
- Low Heat Output Relay
4. MAP Sensor
5. MAF Sensor (can delete with tune)
6. N75 Turbo Valve
7. N239 Anti-Shudder Valve (can delete with tune)
8. N18 EGR Valve (can delete with tune)
9. Alternator Plug
10. Glow Plug Rail
11. Coolant Glow Plugs (not necessary, suggested for cooler temps)
12. Oil Pressure Sensor
13. Water Temp Sensor
14. Injector Pump Plug
15. Crank Position Sensor
16. Needle Lift Sensor
17. Dash Lights
- Glow Plug
- Check Engine Light
- Tachometer (unsure how to interface with Tacoma cluster...)
- Speedometer (unless using non-TDI vehicle's original cluster)
- Oil Pressure Warning
18. OBD Port
19. Accelerator Pedal

Is there anything here that I'm missing or needs changing? Also, I have a few questions I've come across while tearing the stock harness apart that I was hoping someone could answer me, so bear with me lol.

First, in my OBD port I have (had) a wire going into Pin 1 that came from the cooling fan module plug, which has since been removed. Is this pin necessary?

Second, I've noticed in the Haynes manuals that the brake and the clutch have wires going into the ECU. Can these be removed or must they be interfaced with the vehicle they're going into?

Third, is the "Voltage Supply Relay" necessary? What relays, aside from the glow plug relays, are necessary?

Lastly, would anyone happen to know what "AC/ALT Dash Con" would signify?When I removed the electric fan module I noticed that two wires coming from the alternator went into the plug going to the fan control module, yet the Haynes manual shows the wires (4) going into either the ECU (2) or power/ground.

Thanks in advance for any insight people can offer. Looking to make this a super helpful thread for people doing these swaps in the future. Cheers!

Last edited by Tacoma_TDI; September 2nd, 2017 at 04:42.
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Old September 3rd, 2017, 09:30   #2
Bad_Vision
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Glow plug relays are not required at all. You can delete them with the tune and run a simple push button relay set up. This gets rid of the giant VW relay boxes as well as a small relay will fit better for swaps.
Dash lights are also application specific and wouldn't be considered a stand alone as they are not need to run.

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Old September 3rd, 2017, 09:35   #3
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A true stand alone would be considered not using any VW parts other then what is needed to run the engine.

Literally 6 12v fused wires and 1 30amp fused constant wire is all that is needed for the engine to run.
You will need the VW accelerator pedal and ecu. But nothing else.

If your application is desired to have cruise control you will need the brake pedal switch or convert to a similar switch.

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Old September 3rd, 2017, 13:33   #4
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Quote:
Originally Posted by Bad_Vision View Post
Glow plug relays are not required at all. You can delete them with the tune and run a simple push button relay set up. This gets rid of the giant VW relay boxes as well as a small relay will fit better for swaps.
Dash lights are also application specific and wouldn't be considered a stand alone as they are not need to run.

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Thanks for your reply. In my application I've decided to leave the glow plugs attached to the ECU because I'm paranoid of leaving them on for too long (the ECU shuts the coolant plugs off off once the engine has reached a certain operating temp, and the regular glow plugs off after starting the engine, correct?)
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Old September 3rd, 2017, 14:12   #5
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A GP relay and wiring from a Mk1/Mk2 1.6L diesel will also shut off the plugs when the coolant reaches a set temp via a thermo switch. I used one of these setups on my ALH mTDI install.
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Old September 4th, 2017, 05:47   #6
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Some guys have gotten away without hooking up the clutch and brake switches, they are both used for cruise control and anti-shutter when decelerating. Ice seen where some guys were having issues caused by the brake switches not being hooked up. I'm hooking them up just to be on the safe side and in case I want cruise at some point. Brake switches is just a simple circuit with a DPDT relay triggered by the Toyota brake light. I also used the ALH glow plug and coolant glow plug relays because I had them and were able to bundle them up nicely, same with the other relays and fuses. I only ended up using 2 fuses, merged a couple of the circuits to clean up the harness.
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Old September 4th, 2017, 16:47   #7
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The two swaps I have done had been both tuned by Malone and both did not need the brake switch at all but we did not run cruise on ether trucks.

The glow plugs shut off is nice but like I said a momentary switch with a relay is just as effective, the plugs only heat when you press the momentary switch so as long as you don't hold it for more then 30 seconds at a time your fine. And I have not had to use my glow plugs yet in Michigan, this will be my first winter so I'll update that as well.



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Old September 15th, 2017, 16:49   #8
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There are two brake signals that are sent to the ECU on two different switches found on the brake pedal.
One is for the cruise cancel which I believe operates opposite the brake light switch, meaning it opens the circuit when the pedal is depressed.
I just discovered that the brake light switch signal for my 99.5 Jetta controls something called 'left foot braking.' It pulls back power one time after an engine start, if you hit the brake and the throttle at the same time. If you don't hook up the brake light signal to the computer, then it always thinks the brake is on due to not being grounded, which cancels power the first time you try and accelerate after starting the car. Pretty annoying, especially when pulling out of parallel parking into moving traffic. I remember seeing on one tuning and flashing service website, you can send in your ECU to flash this away. Don't know what year cars this 'feature' came on.

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Old September 18th, 2017, 11:59   #9
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Does the ECU require the oil pressure and water temp sensors or are they only for the gauges/dummy lights?
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Old September 18th, 2017, 12:52   #10
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Quote:
Originally Posted by ca180 View Post
Does the ECU require the oil pressure and water temp sensors or are they only for the gauges/dummy lights?
Oil pressure is indicator only I believe.
Water temp controls the glow plugs.
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Old September 18th, 2017, 13:32   #11
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MAF, EGR, ASV, glow plugs, coolant controls, cluster, N75 can all be deleted and/or run on separate switches, however you will still need to plug the N75 valve in and tuck it away somewhere so that the ECU sees that it's there.

I'd recommend keeping the MAF and N75 for road use since they're superior to speed density control and MBCs. If this is a trail rig I'd remove the MAF to avoid getting it dirty. Running glow plugs/cooalant system independently would be a waste of time as well and likely not as clean of an install.
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Old September 19th, 2017, 07:18   #12
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Quote:
Originally Posted by jackfolstam View Post
Oil pressure is indicator only I believe.
Water temp controls the glow plugs.
Does the water temp control the engine glow plugs or the coolant glow plug? When I took a look at the fast forward ALH harness it looks like the sensor wires are just out there to wire in, but it's really hard to see if it goes to the ECU.

Quote:
Originally Posted by Owain@malonetuning View Post
MAF, EGR, ASV, glow plugs, coolant controls, cluster, N75 can all be deleted and/or run on separate switches, however you will still need to plug the N75 valve in and tuck it away somewhere so that the ECU sees that it's there.

I'd recommend keeping the MAF and N75 for road use since they're superior to speed density control and MBCs. If this is a trail rig I'd remove the MAF to avoid getting it dirty. Running glow plugs/cooalant system independently would be a waste of time as well and likely not as clean of an install.
Don't you have to de-tune the ECU if you remove the MAF, EGR, and ASV?

Here's the image of the "FastForward" harness in case anyone hasn't seen it. It has a full delete of the items listed above except for the glow plugs and N75.


https://www.fastforward.ca/graphics/...%20Harness.jpg

Last edited by ca180; September 20th, 2017 at 05:09.
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Old September 19th, 2017, 07:22   #13
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Damn, sorry that's so big
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Old September 19th, 2017, 13:07   #14
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Please use a link or decrease resolution so the thread is legible. I'm not sure what you mean by de-tuned, but assume the answer is no. Speed density can make just as much power. Yes glow plugs are coolant temp dependent.
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Old September 20th, 2017, 05:10   #15
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Quote:
Originally Posted by Owain@malonetuning View Post
Please use a link or decrease resolution so the thread is legible. I'm not sure what you mean by de-tuned, but assume the answer is no. Speed density can make just as much power. Yes glow plugs are coolant temp dependent.
I don't mean a reduction in power, I'm talking about tuning the computer not to rely on those sensors/solenoids/etc...
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