ALH ECU pin-out

Does anyone have a pin description for the ALH ECU?

ECU number 028 906 021 GN
According to Ross-Tech, this cross-references to an ALH (8D)

http://www.ross-tech.com/vag-com/download/label-files/02-01.lbl

I would specifically like to know the glow plug relay pins, but a more complete list would be extremely helpful.

Any information such as voltages for the pins would also be greatly appreciated.

Hey e*clipse,

I might be able to help you if you can let me know exactly which pin voltages you are looking for by checking my alh in the driveway. I can't wait to see that toyota running. I'm a newbie to these forums but I can use a multimeter.

PM your email addy and I will send you it on PDF. I can point you to the pin numbers a little later tonight when I have time.

121/33 - green wire goes to T10e/8 (black connector), then to pin 7 on relay
121/42 - lilac/white wire to T6/2 (brown connector), then to pin 1 on relay

I don't have the voltage at this point, but I will on the weekend.

Hello everyone and thanks for the quick replies.

Perhaps I made a mistake here, but just to be clear, this is a 68 pin ECU.

?? I'm not sure what you mean by 121/33 or 121/43 ??

Are you referring to the newer 121 pin ECU?

According to my Bentley's, those pins would go to ground and the instrument panel respectively on the 68 pin ECU.

1999.5 ALH Mk4 Wiring:
Index:
http://pics.tdiclub.com/showphoto.php?photo=35953&cat=517

Fusebox:
http://pics.tdiclub.com/showphoto.php?photo=35952&cat=517

Instrument Cluster:
http://pics.tdiclub.com/showphoto.php?photo=35954&cat=517

Engine:
http://pics.tdiclub.com/showphoto.php?photo=35955&cat=517

ABS, Fans and A/C:
http://pics.tdiclub.com/showphoto.php?photo=35956&cat=517

Here is some more information regarding the ECU and the wiring harness:

The ECU's part numbers:

VAG: 028 906 021 GN
Bosch: 0 281 001 660
Manufacture date: 22.10.97

This is a German ECU, and it has been chipped by RocketChip.

My confusion comes from the fact that there seems to be a change in the glow plug relay right around 1997. In fact, there seem to be a LOT of changes:

http://forums.tdiclub.com/showthread.php?t=204372

My Bentley's shows a 4 pin glow plug relay for 1997, and a 7 pin glow plug relay for 1998-1999

According to Bentleys, the 4 pin glow plug relay uses 68/50 and the 7 pin relay uses 68/50 and 68/30

Because it is a European ECU, it may use the 7 pin glow plug relay rather than the older 4 pin.

e*clipse said:

Hello everyone and thanks for the quick replies.

Perhaps I made a mistake here, but just to be clear, this is a 68 pin ECU.

?? I'm not sure what you mean by 121/33 or 121/43 ??

Are you referring to the newer 121 pin ECU?

According to my Bentley's, those pins would go to ground and the instrument panel respectively on the 68 pin ECU.

Click to expand...

T68/50 drops a ground for the GP relay to enable the gp's

Thanks for the diagrams, G60ing.

T68/50 drops a ground for the GP relay to enable the gp's

Click to expand...

That makes sense, through circuit 15.

Can this ECU use T68/30 as well? (to control the new GP relay?) I have a 1998 wiring harness with the 7 pin GP relay.

If not, can pins J66/1 and J66/7 (of the 7pin GP relay) be jumpered?

Sorry, I had assumed it was the 121 pin NA ALH

No problem!

All advice is appreciated here.

G60ing: Is the harness I have from a '99.5 ALH MK4?

JSRMonster: PM sent regarding pins 68/50 and 68/30

Anyone: My Bentley's shows on the 1997 wiring harness that pin 68/30 is not used. However, it is used on the 1998-1999 wiring harness.

My ECU is dated 1997 HOWEVER, it is a Euro spec ecu, not a US ecu.

Does anyone have any definative information about whether this ECU uses these pins?

If not, does anyone have any recommendation of where I can find this information?

G60ing: The 1999.5 MK4 wiring harness shows an 80 pin connector to the ECU. My harness definitely uses a 68 pin ECU connector and a 7 pin GP relay, so the wiring harness must be from 1998 - 1999.

All other questions remain open.

Next option would be to take the cover off the ECU and trace wires.

Hey Eclipse,

I am following this thread, and am wondering if there is a bit of confussion here on north american vs euro ecu's and plugs. I don't have the answers but thought I would help try and clarify a few things and may be somebody can correct it or add to it.

North American

AHU engine code (97-99.5, MK3 Jetta) - 80 pin - one plug
ALH engine code (99.5-2003, MK4 Jetta) - 40 pin +121 pin - two plugs
BRM & BEW code (2004-2006, MK5 Jetta) - 130+ pin set-up

Europe

ALH - ? now you say you have a 68 pin connector?
ARL/ASZ - Euro PD's - 40 pin + 121 pin - two plug

G60ing's diagram shows 80 pin connector for 99.5 ALH

JSRMonster indicated 68/50 & 68/30 which would indicate a 68 pin plug, as you say you have. Is your Bently a Euro version? Does it show a 68 pin or an 80 pin. Or are you looking at a NorthAmerican AHU MK3 Jetta diagram?

TDIsynchro raised some good questions.

My confusion(s) are related to the hybrid nature of my system.

1) The ECU is a 68 pin all metal ecu with a port for the manifold pressure.
2) The wiring harness has a 68 pin connector.
3) My Bentley's covers North American 1997-1999 Jettas, Golfs etc.

I've changed a few things, including the MAF (MK4) and turbo (vnt-15). The changes necessary in the ECU have been taken care of by RocketChip.

I think what set things in the wrong direction is a the Ross-Tech cross-reference file. I apologize for the confusion.

All my ECU related hardware & documentation are for a 68 pin ECU.

My main questions boils down to if a Euro ECU from 1997 would be more equivalent to a North American 1998-1999?? (all 68 pin ECU's)

So do you actually have a wire diagram for the 68 pin ECU? Or do you just have the 80 pin wire diagram?

Differences between 1997 and 1998/1999

The wiring diagram(s) I am working from are for 68 pin ECUs.

I've picked through my Bentley's manual, looking for all the differences between the 1997 and 1998/1999 68 pin ECUs. Here is what I've found:

mystery solved

It occured to me, I had the answer to my question already.

Before Jeff @ RocketChip sent me my ECU, he tested it. He felt this was important because there were so many mods done to the ECU. For example, there were some issues with the maf due to the immobilizer defeat. I really appreciate his thoroughness in doing this job.

He emailed me the results of the test:

I was very pleased during testing yesterday, and it worked well in my boy's 98 jetta with vnt17 turbo and A4 maf, and cruise worked too. You'll need the brake and clutch switches functional for cruise control (4 switches).

Keep me posted of your progress.

Click to expand...

The verdict: (with regards to the ECU/GP question) The ECU worked with a '98 jetta, which uses a 7pin GP relay. No harm was done during the test, so my concerns have been answered. I'm still not sure if BOTH circuits of the GP relay are closed, or only one (by pin 68/50) I will do futher testing to figure this out and relay the results later.

1Z & AHU wiring diagrams. This where it gets tricky because there are 2 diffenert glow plug circuits. The early:
1996-1997 TDI Jetta
http://www.haywood-sullivan.com/vanagon/TDI/1996_Jetta_TDI_wiring_LONG4.pdf


and then the later style:
B4 Passat Wiring:
Standard Equipment:
http://pics.tdiclub.com/showphoto.php?photo=35958&cat=517

Engine:
http://pics.tdiclub.com/showphoto.php?photo=35957&cat=517

the wiring harness you have is for the newer style glowplug setup where the GP relayd does not mount on the fuse/relay panel 1st 12 relay spots but instead has an aux relay that mounts to the side of the relay panel.

I ran into a minor issue because my car's ecu, is made for the 98 and I'm using the early style wiring harness that has the relay mount on the relay panel. When I need to check wiring I use the Haywood diagram.

As I have recently learnt, some of the Euro models did not use a 7 pin "smart relay". They used a 4 pin "dumb" relay. This requires only one wire from ECU to ground the circuit for energizing GP. Are you sure you do not have this set-up? You can use any 50Amp relay for this type of GP control.

30 = battery power = the 50A fuse for the GPs.
87 = switched power to the GPs (what 30 connects to when the relay is activated).
85 = grounding control by the ECM (in your case at 68/50)
86 = fused ignition switch power

TDIsyncro said:

As I have recently learnt, some of the Euro models did not use a 7 pin "smart relay". They used a 4 pin "dumb" relay. This requires only one wire from ECU to ground the circuit for energizing GP. Are you sure you do not have this set-up? You can use any 50Amp relay for this type of GP control.

30 = battery power = the 50A fuse for the GPs.
87 = switched power to the GPs (what 30 connects to when the relay is activated).
85 = grounding control by the ECM (in your case at 68/50)
86 = fused ignition switch power

Click to expand...

yes and some of the early USA passats had this wiring. Here is the schematic:
1996-1997 TDI Jetta
http://www.haywood-sullivan.com/vanagon/TDI/1996_Jetta_TDI_wiring_LONG4.pdf

Look at the diagram around tracks 63-70 as they show the 4 wire relay, the 50amp fuse, the T68/60 ECU wire and the 4 glowplugs.

My Bentley's shows essentially both wiring diagrams.

As G60ing said, I have the "smart" 7 pin GP wiring harness (he sold it to me)

TDIsyncro:
As I have recently learnt, some of the Euro models did not use a 7 pin "smart relay". They used a 4 pin "dumb" relay.

Click to expand...

What I don't know is whether the ECU controls pin 68/30 AND 68/50 or just 68/50. Syncro - do you have any more info on this??

It appears that AT LEAST the ECU works and is not damaged if it is used on a car w/ the "smart" 7 pin GP wiring harness.

I did take the case off to see (and measure) if there are any similarities between pin 68/50 and 68/30, and so far the answer is inconclusive/negative.

As Jeff said, the pin will be pulled to ground if it is activated. I should be able to verify if the pin is pulled low by measuring voltage from 85 to ground. A large (1MOhm) resistor bridging 86 to 85 will function as a pull-up resistor. This should limit the current to protect the ECU in the event that there should NOT be any voltage/current at pin 68/30.

Also, from my chart on post #17, it looks like this should be the only concern if the rest of the harness is wired correctly.

Feedback anyone?

e*clipse said:

My Bentley's shows essentially both wiring diagrams.

As G60ing said, I have the "smart" 7 pin GP wiring harness (he sold it to me)


What I don't know is whether the ECU controls pin 68/30 AND 68/50 or just 68/50. Syncro - do you have any more info on this??

It appears that AT LEAST the ECU works and is not damaged if it is used on a car w/ the "smart" 7 pin GP wiring harness.

I did take the case off to see (and measure) if there are any similarities between pin 68/50 and 68/30, and so far the answer is inconclusive/negative.

As Jeff said, the pin will be pulled to ground if it is activated. I should be able to verify if the pin is pulled low by measuring voltage from 85 to ground. A large (1MOhm) resistor bridging 86 to 85 will function as a pull-up resistor. This should limit the current to protect the ECU in the event that there should NOT be any voltage/current at pin 68/30.

Also, from my chart on post #17, it looks like this should be the only concern if the rest of the harness is wired correctly.

Feedback anyone?

Click to expand...

If your going to insist on using the smart GP then you have to have 68/30 & 68/50 hooked up. That would be as per the wire diargam Passat 1Z posted by G60ing. If its just 68/50 thats working for you, then you will have to use a 4 pin GP.

smart GP
Pin 1- 68/50
Pin 2 - 50 Amp Fused
Pin 3 - Ground
Pin 4 - GP's
Pin 6 - GP's
Pin7 - 68/30
Pin 9 - From J317

As you mentioned, it did not get damaged at Jeff's, just hook it up and see if it will energize the relay or not. If not, then you will have to get a dumb relay and use just 68/50. I can't offer anything else as I do not se the schematics your looking at and neither one of us knows if they are the right ones or not.

Ok, you talked me into it. In fact, it looks pretty dumb to use the "smart" GP relay.

A minor mod to the plug, and I can fit a standard 50A relay. Cost: $5.00 for a good Tyco relay.

If I want overkill, I can get a 75A relay for $21.

On another topic, I was verifying voltages at the sensors ( G70 MAF, G73 AIT, G81 Fuel Temp Sensor, etc)

The positive 12V voltages are correct.
The ground is not. It appears to be floating - not connected. I don't see where it should be connected in the schematic or my harness.

Should the circuit 220 - sensor ground connection be connected to the engine or the chassis? Where is the connection <usually> found?

Thanks again for all your help

d'Oh - found it!

Thank you G60ing for the nice schematics (from haywood-sullivan.com) It's much more clear than the Bentley's schematic, though it shows the same thing.

Pin 68/33 is instrument ground. I was able to verify voltages & grounds by bridging 68/33 to 68/24 (common ground)

With all my, um, confidence I then plugged in the ECU...

For some reason, voltages at the sensors that should have read 12V measured 1.5V. Hmmmmm.

After verifying that I didn't have blown fuses, etc. I found the problem:

I used the 'Yota power supply relay. This is not a problem in itself, except Toyota wires the relays different than VW. Toyota applies 12V to the solonoid through the key-on, and grounds the other side of the solonoid at the relay box.

To verify things worked (the Toyota way) before connecting the ECU, I bridged pin 68/38 to pin 68/42. This provided 12V to the relay's solonoid and turned it on. This would energize pins 68/23 etc.

HOWEVER.... It appears that VW energizes the power supply relay (109) by pulling it to ground through the ECU.

Please take this as a warning.. I hope I didn't fry anything...

Update on relay issue:

As I described in my last post:

The Power supply relay shares the Vin with it's switched input. To activate it,the solonoid needs to be pulled low by the ECU at pin 68/42.

Everything works so far; the sensors are getting 12V as required, etc.

There are a couple more questions:

1) The 5V reference @ the MAF measures 7.19V, not 5V - how important is that?
2) When turning the system on, the MIL light turned on (expected)
3) The glow plug light first turned on solid, then started blinking at a constant rate. What does this mean??

I think you are right on on the power supply relay.

2)If it doesn't come on it means your ECU is not getting power.
3)Are you brake switches and clutch switches hooked up yet? That is probably the source of the blinking GP light.

Hi Spulen!

Since the last post, I've made some progress:

Right next to the 80A fuse in relay block 2 (of the Yota) is an open fuse space for a similar fuse. I found a 60A fuse and was able to wire the fan circuit to that fuse. Looks almost OE.

Regarding the VW ECM behavior:
After I made sure all sensors were connected, I tried the system again. Here is what the system does:

When the key is switched "on" (past ACC but not start) the MIL light and the glow plug light both light up steadily. During this time I tried to measure whether there was continuity between 68/50 and ground and 68/30 and ground. Remember I have a 7 pin GP plug.

I measured 70 Ohms between pin 1 on the GP relay (68/50) and open circuit on pin 7. 70 Ohms seems kind of high. Any ideas?

After a bit, I heard a "click coming from somewhere in the engine compartment (my ECU is in the cab) and pin 1 of the GP went open circuit.

At approximately that time, the GP light turned off. This might be good...

Still later, the GP light started blinking...

Spulen81:
3)Are you brake switches and clutch switches hooked up yet? That is probably the source of the blinking GP light.

Click to expand...

I was under the impression that the clutch and brake switches were only important for the cruise control. Am I missing something?

the glowplug light will blink if you have a bunch of errors like sensors being unplugged. I know when my Corrado's brake switch was failing it began blinking and the switch ended up having bad contacts. This is for my 1998 AHU TDI Corrado