MK4 polo failed to connect/communicate with ECU

[mk4polotwist]

Hello all forum members,

I have just joined this forum but have read several threads related to this topic.

I have EPC light come on and after a short period of time (usually within a day), the automatic transmission locks-up (cannot shift from Park).

Hooking-up generic cheap scanners to a bit more accomplished scanners claiming to be made for VW and Audi vehicles have failed to communicate with the ECU.

Having read various threads on this forum, i have checked the OBD2 port pins:
Pin 16 has battery voltage ~12.6V (scanner powers up)
Pins 4 and 5 have good ground. Voltage at pin16 measured against these grounds.
Pin 7: K line has 0.10V.
Pin 6 and 14 : CAN LO & HI has no voltage. However with ignition on, there is a resistance of ~67 ohms. With ignition off these pins show they have no connectivity. I understand, that in this scenario it should read 60 ohms +/- 2 ohms.

I have removed all fuses and continuity-checked with multimeter. They are all good. I have even tried removing the fuse for the radio ( which appears to be factory fitted) in the hope it might rule out any K-line signal interference issue due to after market radio (if it happens to be one).

I am looking for help to sort issues with lack of voltage on CAN Hi and LO pins and ultimately resolve connectivity issue. Which hopefully would help identify the cause of EPC light.

Many thanks in advance.

[littlepolo]

what engine is that and what is the odometer reading?

not sure if it might be worth a try to disconnect the battery and reset the ECU?

[mk4polotwist]

Hi Liitlepolo

Thank you for your reply.

Engine: 1.4 75 Type: 9n

Odometer: ~42.6k

I have been resetting rhe ECU by disconnecting the battery to get rid of the EPC light.

Dont want to carry on using the car this way as i do not really what damage it might be causing.

Can really do with the OBD2 port ECU comm working.

Thanks

[littlepolo]

can you confirm which scanners exactly you have used and are they known to be good (i.e. work on another VAG vehicle)? only time I had a problem was a cheap product with a cable issue. are you sure the shift lock is working/releasing correctly (is there a click when on the brake pedal)?

[iichel]

i'd recommend to find a wiring diagram and see to what the can diag lo/hi connect. might be connected to comfort module or cecm or gateway.