EVAP Cannister & Knock Sensor

[cwbrock]

I am really at a loss about what to do and desperate to find some help.

I own a 1996 Nissan Maxima, and recently failed my emissions test because of the following codes: P0325 and P0446. I am not too worried about the P0325 code(Knock Sensor), since that should be an easy fix. However, the P0446 code (EVAP Cannister Control Valve) is troublesome, even when I attempt to reset the code, it shows up instantly.
Under normal conditions, when the car is turned on, the ECM activates the EVAP Canister Control Valve. Currently, this does not happen. I followed the diagnostic procedure and removed the valve and tested it, it appears to work just fine when it is connected directly to the 12 volts battery. I checked all the connections and such and everything checks out OK. When installed, it will not activate when the car is turned on. I traced the wires to the ECM and get a 12 volt reading from the return wire (Pin # 70), which is what I would expect. When I ground pin #70, the valve will activate.

This led me to believe that the ECM was faulty, so I replaced it (with a rebuilt one). When I installed the new ECM, the problem did NOT go away. I checked all of the grounds into the ECM to make sure one of them was not open, and they all tested OK.

So, I am left with only the following conclusions:

1) The new ECM is faulty, exactly the same way as the previous one.

2) The new ECM was good, however, because of some other electrical problem, simply plugging in the new ECM, damaged the new ECM exactly like the old ECM.

3) There is another problem with some other component that also generates the P0446 code.

Any suggestions? ideas?

I can not afford to continue and purchase new ECM's when I not sure that it is even the ECM. The only other information to know was the code began to appear immediately after I got the car back from the collision repair shop, because it had almost $4000 in rear end damage from a collision. Before I got home, I drove the car home and the light appeared before I got home (15 miles). I took it back several times, and we fixed a warranty recall issue, they took it to the dealer and the dealer told me that they traced it back to the ECM, which led me to diagnose the problem myself to determine that it possibly was an ECM issue.

[jmd102]

Hey there CWBrock, if you like I can see if I can get you a wiring diagram from work tomorrow and possibly a flow chart to diagnose the P0446. Do you have a fax number?? If so I could shoot you a buch of info. Lemme know and I'll see what I can do. I have a crap scanner so emailing the documents would be difficult.
Mark

[cwbrock]

I have the wiring schematic for what I believe the code is, from alldata.com. It just shows the circuit for the evap canister control valve, nothing else.

I just read a Tech Bulletin regarding the possibility of an evap breather valve. It is not on the circuit, but supposedly, it will activate the same code. If there is more to it, I will give you my fax, but I don't want to post it here.


Chris

[jmd102]

If you like you can send me a mail to: [email protected]
I can use the company's fax machine no problem.
Possibly any extra info I can send you can be helpful.
We use Mitchell On Demand, although I wish we had Alldata sometimes. See what I can find for you!
Mark