Non Starter, 17925 - Power Supply Relay for ECU

Yes the MIL will be on Key On Engine Running ( if it were connected) as the ECU will think the coil pack, injectors and so on are not powered with the lack of feedback or current draw on pin T121/23

MIL connection described in the last column but not required as you say.

 

So, Swapped the pin on the T14a and i think the injectors are firing now. I can smell it but they are not soaking, Should they be? The fuel pump is working on cranking as i can hear it sticking my head under the car.

Im only left with no spark now. I have pulled a plug out and put it near something metal and get no spark on cranking.
I have 12V to T2/1, This drops slightly when cranking to 9-10v. I have this connection going to G1/10.

Obviously i still have the error, But why is it not firing. Could the error be the problem?

 

Ok, Spent a few hours looking at the diagrams tonight.

Im sure i have it connected up correctly, But becuase this fault is logged, Would it stop the rest from working?

The pink T121/23 wire is not to earth, Its just taped up in the loom but i can get to it. Would there be an easy way to clear the fault with doing something with this wire but not adding another relay?
With welding the MK4 pedal in and the rollcage, it is pretty tight behind the fusebox!

 

could you not tap in to the wire some where else in the loom thats easy to get to . might mean unwrap
some of it.

 

ECU PN is: 022 906 032 BG
ME7.1.1, Engine is a BDE

 

It is the 24v BDE diagram that was used to understand and config to an older MK2 using VAG current paths for 1989-1990 MK2 8v GL and GTI.
I would also suggest any tappings to KL30 be fused!
ECUs do stay awake for a few secs after "Key Off"

The 24v ECU has logic , linked to calibrated fault paths, so you would require a certain current, within a window to flow through the T121/23 to "heal" the fault.
I looked at this very late at night and could not see an accessable path to the Digifant relay control earth from the diagrams I have here. The diagrams I have suggests the Digifant relay (Pos3) is connected to the internal fusebox rail (31) and switched on by KL15. Based on this diagram and the understanding of what goes on (logic states) in the 24v PCM I did not recommend using G1/7. I am not in front of my diagrams as I am at work so your suggestion of using the 021**256' VR6 PCM relay maybe an alternative to the my suggestion of using a standalone relay circuit to clear the fault providing the relay control at KL85 is not shared with any permanent earth. I do not have my MK3 stuff with me so we will have to take your word on this.

The ECU is working as you have diagnositcs. However you can inhibit outputs such as spark control when there are issues such as immobliser ( which is not a pending, present or imtermitant fault)
With these newer Ecus you have to "think inside the box"!

Lets work with each other on this one matey.

 

I just had a thought as I am not in front of any diagrams.

Orginally as COPs, VVT and Injectors and supplied +12v by the same source (J271) what tells the J220 to set T121/23 low i.e. what wakes up the ECU to suggest the car is being cranked, KL15 or CAN?
If we do know this then are we getting pin T121/23 to be true i.e. pulled low?

(supplying 12 Volts to outputs is just bypassing ECU control by not logic)

 

Wow, Im getting lost here

Trying to find the trigger wire but cant find the end, I know its taped in the loom somewhere.
I have power to the coil's but its like the ECU is not sending the signal to spark

 

John, The VR6 PCM is not a CAN based PCM and does not stay awake or wake up with the Key Off.
You may not be worried but the Electrical Team of Engineers at Bosch/VAG were concerned to add a 20 amp fuse in the current path.

The diagrams you have from the ETOS are the same I have at home. However as this was a MK2 (albeit with a VR6 conversion) I did not look at MK3 stuff at that late hour. Can check it out later though when I am home and include in the table that was created.

Which suggests the ECU is powered as I can do on a bench tester. In later cars you can access the ECU via CAN which will wake it up if the key is off.
What happens on ECU powerup sequence regarding outputs (Pin 23) needs to be further investigated.

Some of us go a bit beyond solder and wirings...

What you say is logical....for older stuff and leads to a finite path of troubleshooting. The logic in this ECU is providing the current path for the fuel output and we found a supply from an source other than where we should (J271). An alternative method to J271 +12v supply was done for coil packs and vvt solenoids.
However my question remains what gives the instruction to wake up the ECU. When this happens would pin 23 be pulled low)
I am of the belief is if this goes low via CAN/KEYON then the logic for that enables the VVT solenoid and COPs will be switched on and the engine will run. The fuel injector logic is seems separated from these.

 

The issue was shorted listed to the diagram and table that I modified and put up earlier mate.
I would suggest attempting to understand how does T121/23 go low and how the ECU awakes up when the vehicle key is "ON".

I mean KEY ON/or CAN msg that KEY is true -> T121/23 goes true -> IGA/VVT internal path active-> KL87/ Pin 4 (J271) +12v -> IGA/INJ/VVT live.
As said there is logic going on behind the ECU connector.

 

I just thought I give a little input on this from the controls side.
But I am busy again so will check back later to see how you all get on.

HTH

 

Ok, My connections are this:

G1/8 - Blue/Yellow - Lambda probes
G1/8 - Yellow/Black - T141A/6 - Fuel Pump Feed
G1/10 - Black/Purple - T121/3 & T6/1 - Switched ECU Live

G2/4 - Black/Purple - T141A/2 & T141A/8 - Injectors & Speedo Sender
G2/8 - Red/Purple - T141A/5 - (I now see this is not needed)
G2/9 - Red/Green - T121/62 - Constant ECU Live

T141A/7 - Earth. This is just a chassis earth. Should it be in the fusebox?

Obviously i have all the other senders and stuff connected but i cant see them stopping it running.

The one im missing is T121/23 (ECU trigger we are still not sure about) but when i turn the ignition on i can hear the relay click on and the TB moves etc, Also im able to diag it.

To me it seems something simple is missing, What bext to check next? Thanks for your help both

 

Surely your T121/23 will need to see 12v, as the wiring diagram shows the ECU would make make the wire go from open circuit to earth to trigger the J271 relay.

Why not jus wire up up as per the diagrams?

 

If its as simple as putting 12V to T121/23 then it will be great, But i need some info on that first.
I was trying to simplify the loom, Its nearly there just this problem.

 

Cheers Jonny.
You made one for benthejettaman too and he also has a BDE engine, His works[:^(]

T14a i mean sorry, Yes
Any harm in putting 12v to T121/23?