I just picked up a 1996 Discovery with 144K on it. It was not supposed to have any issues but when I got it home the Check Engine light came on so now I am vehicle less as I cant register it until I pass an emissions test. I am getting P0446 and P1447 codes. I can connect a meter across the connector on the valve and get 12V I dont think the ground is actually actuating in the ECU, I think the meter is sensing a ghost ground so I read 12V but the valve does not open. I powered the valve and it works fine. The guy that had it replaced the ECU sometime in the past. I saw a thread here posted by Disco Mike in regards to what ECU/ECMs are swappable but now I can’t find it. I have a MKC104620 in it now and the Disco runs. I also have a ERR7377 module that the previous owner bought as a backup, which does run the Disco. Are these two modules swappable? I can remove the tank line from the charcoal canister and the gas tank will stay pressurized, is this normal? I can pull a steady vacuum or apply pressure to the tank line at the canister and I do seem to have flow, just very confused about the tank staying pressurized. Is there a check valve in the vent line? I did have a bad gas cap but that was swapped out first thing. So do I have two problems, vent lines at the tank and ECU trigger of the ground for the purge valve? Waiting for shop manuals to arrive to help trouble shoot but any help would be greatly appreciated. I am on my knees praying to the mechanical gods for deliverance.

 

So I am not getting ground from ECU, does anyone now what what triggers the ECU to switch ground to purge valve?
Are there any grounds I should be aware of that could cause this. Rover manual is very week on troubleshooting DTCs

 

You can download the manuals free look in tech section, wish I could be more help but my truck is ael

 

So, as an update. I have determined that the ECU is not the correct one for a non-Evap disco. So I ordered the correct part number. Still not sure how the Non-Evap systems trigger the purge valve but I guess I will have to wait for the new ECU to continue troubleshooting.+

 

Is your caniste round or square? Mine is square which is ael which has a pressure switch in the fuel sender to work that purge valve, also uses a different fuel cap

 

Round evap. Keep getting same codes. New gas cap and valves. What triggers the ecu to triger ground to Purge valve. Do you think i have a bad sip valve.

 

Sorry idk on non Abel, I am sure sOmething simple

 

Advance Evaporative Loss equipped engines (which both your ECU's are for) have a pressure sensor on the tank mounted fuel pump, yours being Pre AEL does not. The missing ECU internal ground latch....... Being that you have a 96 you should never have received this MIL in the first place.

Sounds like you'll have it sorted out if you ordered the correct ECU. Pre AEL have a simpler purge routine.