Mini MPI - K line fault

Hi! Not sure whether I've got good or bad news :hgf: :lol:

The voltage is 12.70 V on the battery and 5.14 V between pin 18 of the black connector and the ground, so I guess we cannot conclude that the ECU is not working. The Pscan was not connected.

Should I measure the voltage on pin 18 while Pscan is connected? Would this tell us something?

Many thanks!

David106 wrote: Hi! Not sure whether I've got good or bad news :hgf: :lol:

The voltage is 12.70 V on the battery and 5.14 V between pin 18 of the black connector and the ground, so I guess we cannot conclude that the ECU is not working. The Pscan was not connected.

Should I measure the voltage on pin 18 while Pscan is connected? Would this tell us something?

Many thanks!

No it won't make any difference.

Hello David

Did you make any progress with your MEMS2J ?

Hi Philip, all,

First of all, apologies for the long time with no news from my side. So, as a well deserved update, I'm afraid I never managed to find another MEMS2J to borrow, so I decided to buy one. After quite some time, I found one in the UK and had it sent to Spain - it comes with the airbag module and the FOB.

So I've got the pscan tool, the old MEMS2J, the new MEMS2J, and a big question, what should I do first?

I guess I shouldn't throw the new MEMS2J at the car straight away, as it could get damaged if whatever is wrong was in the car. Maybe a wise thing to do would be to run the bench tests to check that the new MEMS2J works properly, right?

Any suggestion is more than welcome!

Thanks!

PS. Yes, the car has been sitting in the garage during all this time :bang:
PPS. It's great to be back

pscan.uk wrote:

David106 wrote: Message Init fail - Is this the expected behaviour?

This is consistent with three scenarios.
1. MEMS2J ECU not powered and so not communicating.
2. MEMS2J ECU powered but damaged, so not communicating.
3. pscan damaged. However this is not likely. pscan has sent a pulse onto the K line and detected the pulse (if it did not, then it would say K line fault). Also pscan working on the Golf. Therefore pscan is not damaged.

I've made some good progress today.I tested the old MEMS2J ECU - just to get familiar with the whole thing again - and the expected "Init fail" message was displayed.I then tested the new one and it worked perfectly, it connected successfully at the first attempt! :woo2:


So, from the three possible scenarios above, it seems clear that the old MEMS2J is dead.

My concern now is that there might be something in the car that damaged the ECU, which would damage the new one as well if I just plugged it in.

For context, the car was running perfectly when we decided to strip it down to paint it and change some rusty parts. After assembling it back it never ever turned on again. Might it be that there is some cable wrongly connected that would have damaged the old ECU? Any advice as to where to start looking? or would you just install the new ECU and try?

Any advice is more than welcome

Thanks!

I think that you will have to get a wiring diagram for your car and go through every pin on the ECU connector to make sure that the voltages that you see are consistent with what what the pin is supposed to do.
If a pin on the ECU connector goes to a connector at the other end (for a sensor or something) then disconnect the other end and check that the wire isn't shorted to chassis or 12V.
When there's nothing left to check then it's always possible that your old ECU died from a age. Vibration, heat, dry solder joints etc can cause these things. Nothing lasts forever.

Thanks Philip!

I decided to start with one particular set of pins in the ECU connector, as something strange is happening.

Right after connecting the battery, with the ignition off, the temp gauge goes all the way up. Switching the ignition on doesn't make any difference. This is a short video I uploaded to YouTube for reference.

My observations and assumptions are:

- This only happens when the black connector of the ECU is connected to the old ECU (haven't tried with the new one). If that is not the case, the temp gauge doesn't move.
- There seems to be two pins involved, number 31 for Coolant temperature gauge and number 25 for the Ignition coil.





- Having the temp gauge showing high temp would mean that the resistance of the temp sensor is very low. I checked the sensor resistance at room temperature - roughly 10ºC - and it showed 2.8 kOhm, which seems consistent with the expected value.

- Might the ECU itself short the sensor wiring to ground, therefore making the temp gauge show high temperature? Is there any way to check for this?

Any ideas?

Thanks!