Hey Everyone, Long time lurker, first time poster.

I have a 2002 Discovery 2 that is new to me, I don't know the history. I knew it needed head gaskets when I bought it, so I just finished those up. There were also a couple EVAP codes that keep coming back on me: P1451 and P0447. I started with the "throw parts at it" approach, so I've replaced the purge valve, the leak detection pump, the charcoal canister, and the gas cap.
Now that those didn't work, I am trying to be more nuanced in my approach
The RAVE manual says P1451 is Lead Detection pump, open circuit. So- electrical issue?
I have good power to the pump when the ignition is on. When it is off, I have just 1.2v, not sure if that is what it should be.

Here is where I am confused. The manual says
"The pump is operated at the end of a drive cycle when the vehicle is stationary and the ignition is switched off."

BUT, it doesn't have much power when the ignition is off. Its powered by fuse 2 in the engine compartment, which is controlled by the main relay.

My questions are:
Do you think I am barking up the wrong tree? Maybe I got a bad DMTL pump and just need to try that (again)?
If not, how should I be testing this? The code says open circuit- I know it doesn't have power after the drive cycle, so I agree that its going to look like an open circuit.

Any ideas are appreciated.




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To add to my own confusion, the RAVE manual lists P0447 as the canister vent solenoid. I have the evap system that doesn’t have one of those- just the leak detection pump. I was hopeful that by fixing the P1451 maybe the other one would go away, but I’m no so sure. Could this be an ecu issue? They fact that I don’t get voltage after the drive cycle and a code for a component that doesn’t exist in my car makes me wonder.

 

Excellent job on posting the screenshots from the Rave to help us troubleshoot. So first thing to know is that 99-02 is different than 03-04, so lets make sure you are using the right manual for your truck.

Did you try bench testing the solenoid valve and pump? Of course you can ohm out the wiring to the pump and solenoid. Then the other thing to do is to jumper the wires at the ECU to see if you can make it run.

 

Thanks for the reply. The manual I have says "Discovery Series II WORKSHOP MANUAL - 1999MY ON" The wiring diagram is from 2003, I couldn't find any others, but the colors seem to match up other than the fact my Lead Detection Pump has 4 terminals instead of 3 (12v, pump, solenoid, heater). I did bench test the pump and heard the pump come on. Great idea on connecting right to the ECU. That will be my next test!

 

I thought I would report back what I figured out, hopefully it’s useful to someone sometime.

After a few more dead ends, I decided to check the wiring from the leak detection pump all the way to the ECU. Previously I’d only checked it for the pump to the wiring connector next to the fuse box.

Low and behold, the two wires I needed were not there. It appears that at some point, the wiring harness that goes through the firewall had been replaced, and they used the version made for use with the vacuum evap system rather than the positive pressure design I have. I finished the run of those two wires, and it works! No codes.

One note: I was getting the code P0447, which as I previously mentioned is listed as the Canister Vent Solenoid (CVS) in the manual. If you have the positive pressure system with the leak detection pump, you don’t have the CVS in the engine bay. I’ve learned that in that case, that code relates to the solenoid in the leak detection pump. It’s logical, but I was sure confused about that bit for a while.

I didn’t know much about LR Evap systems before, but now I feel like an expert. That’s why we drive these, right?

 

seriously nice work figuring that out!

 

And thanks for letting us all know.

 

Guess I'm a little late to the game on this one bit I'm having this same exact issue on mine right now. Which pins on the ecu and which ecu are the wires supposed to be tied into?

 

Someone very knowledgeable may know how to advise you on this.... but the RAVE would be your friend here. One of the frequent contributors keeps the link to the RAVE in his signature below his posts....

 

I may need a better version of the rave; I have a version on my phone and my laptop. I've been going through it and dug into my Disco today to see the ecu may have been changed by one of the previous owners. I just can't find where it says the spot the wire is supposed to land on the ecu for the vapor canister vent valve which is most likely the cause of the trouble code.