Topic

Dgriff wrote:

OK, I have received the hardware and connected to the car. I am now able to progress further into the program which is encouraging. Selecting "Petrol" and "MEMS 3" gets me to a window that is telling me, checking "Checking K Line" and then "K line fault". Seems unusual as I used to have a diagnostic tool that would read the ECU info on this particular car. In anycase I will check the K line continuity/power/connection between ECU and 16 pin plug. Begs the question as I cant find a definitive answer....which pin connections am I checking and for what?...earth, continuity, power? With Thanks DG

PS - I did see the post for..." Mini MPI - K" line fault with an identical problem but not sure if the MEMS 2J would be the same.

Which vehicle are you connecting to please?

MEMS 3 MGF SARRDWBGB2D534623

Normally K line fault means that the diagnostic wire is shorted to ground or +12V or that the tool is damaged.
When you connect to MEMS3 this will be pin 7 on the diagnostic socket.
Try an ECU that's on a different line, such a EC5RC5 airbag ECU.

Well, did some wiring checks...I wish I could say there was some logic to the erratic readings I got. High resistance short (3.5K ohms), open circuit to earth and then continuity returned, seemed to stabilise on 75ohms...?. Noticed I had continuity on a number of pins at the ECU. I need to chase a wiring diagram that I have buried somewhere to make some sense of it, mainly colour codes, but the scan tool is up and running. The culprit is a suspect K Line wire as it runs under the MEMS 3 ECU support plate NS passenger lip of engine bay. Continuity readings jumping around wildly while pushing and pulling on wiring in this area. Released trapped wiring and uncovered wrapping expecting to find damaged insulation etc on a number of wires. Cant say I found any external damage so I guess there is something amiss internally. With all the prodding and twisting it seems to have sorted my K line fault issues completely and I can interrogate all relevant areas of the ECU. I'm not saying its sorted but it does prove the working potential of a Monterey 12.1 MacBook Pro with Pscan installed. I will persevere and keep the thread updated as I go. Cheers to Pscan UK.

Please be careful.
The one thing that I suspect will destroy a pscan is if a K line is shorted to +12V.
If it's shorted to earth it won't matter.
Normally with the MEMS3 the K line is internally pulled high inside the ECU through a pull up resistor.
If you check the K line with a voltmeter you should normally get something near to +12V.
If you short the K line to earth through an ammeter the ammeter should show a few milliamps (like 10-20 mA or so).
The problem I have as a tool developer is how to tell if a K-line is shorted to battery/ignition or not.
According to the ISO standard the K line should be pulled up by the diagnostic tool and not the ECU. Therefore if I poll the K line voltage it should be low, and then when I apply a pullup it should be high. This would be a "good" result which means that it's safe to try communicating on that line.
The problem is that MG Rover didn't follow the standard and just connect the K line through a pullup inside the ECU, so, if I poll the line I will always get 12V; this could mean that everything is normal, or, it could mean that the K line is attached to battery and talking to it will destroy my driver chip. There's no way to know. Thanks MG Rover

Just digesting your last reply....So I gather by your message, there is a realistic real world chance of uncontrolled 12V finding its way onto that circuit? Out of curiosity are we talking an internal ECU situation or external? Can you not incorporate a test button with associated stop/go LED (or a globe needing more than 20-30mA to fire up) to interrogate the K line before attaching scanner to computer and from a wiring point of view, before the driver chip?

Anything is possible, but it all adds to complexity and cost. The sixteen pin connector has three pins allocated to earth and +12V, and of the remaining thirteen, MG rover used about eight of them for different purposes. Having check circuitry for all eight would be expensive.

The probability of this actually happening on an unmodified car is very low, however there are certain non MG Rovers where this presents a risk, for example 1980s Peugeot used to connect one of the diagnostic lines straight to the radiator fan positive feed.

If it worries you then you can make a cable connecting the line that you want to test to a 5W side light bulb. If there is enough power on a line to light a bulb then something is wrong.