rocketman4321

I'm getting an occasional-but-increasingly frequent CEL with a sole P1426 code. I pulled the N80 valve and tested it--clicks and flows as expected on 12 volts. Banged the inlet port on the bench and got no crud. So it seems OK.

All the CELs have occurred on a warm restart. Tonight it was about an hour after I'd driven home (10 miles/20 min). Last one happened after an hour or two, and on a damp night. I have noticed that my voltmeter comes up a little slowly sometimes when I start the car, and of course that's worse if I flick the lights on immediately (which I didn't do tonight, but did the time before). Could that be related? On a warm engine, does the ECM try to run a canister purge immediately, and maybe there's just not quite enough voltage to snap the valve open?

rocketman4321

At the risk of bumping a dead post, I did get a little more data tonight. Very hot day, again drove home, restarted 45 min later and drove about a mile with no CEL. Parked for an hour and a half. When I restarted it then, it was getting dark and I thought I had full voltage. The A/C came on with a lot of blower, and when I turned on the headlights I got the CEL (same P1426) and the voltmeter was just over 12 V. It rose to 14 shortly after that.

So could this be an alternator with sticky brushes or harness drop under load, leaving too little voltage to open the N80 valve properly? Anybody know how the canister purge works? Or does the code mean that the computer has actually read an open circuit in the valve coil?

Thanks!

4Driver4

At the risk of asking a stupid question...

How new is the temp sensor? I think that test is only supposed to run under light load when engine is cool (not sure, don't quote me). But a bad sensor will tell the ecu that the engine is cold when it is warm or vice versa, so it may get a result it doesn't expect.

rocketman4321

The coolant sensor is at least several years old. Good point on it confusing the ECU, but the first warm start was fine. For the N80 valve itself, I bench-tested it with a small 12V battery, so the ECT sensor and the car's wiring wasn't in the loop. I'd pulled the valve when the car was cold, so it's also possible that the N80 solenoid is shorting when hot.

Is the P1426 code derived from an electrical measurement (like current when the ECM drives the coil) or from airflow and mixture readings at the MAF and O2 sensors?

georgeb944

If you have VCDS, you can test everything that operates the N80 valve with one of the output tests.

Not only is the valve a possibility, but also the wiring to/from the ECU and the Fuel pump relay...

With a generic OBDII tester, chances are that you cannot.

rocketman4321

Resolved at last. The N80 valve coil fails open-circuit when hot, and only after enough time to heat soak with the car hot but stopped.

Last night, I went out after dinner (car home maybe an hour or so) and I couldn't clear the N80 valve code (P1426). Despite it being fine when this all started, I retested the valve and it read open, and the 070 test won't run with a code. This morning the valve read normal resistance. Tonight, I successfully ran the 070 valve test when I pulled in the driveway--car certainly up to temperature after a 20-min drive. Now, 90 min later, the valve reads open again.

But I haven't had the code on longer drives. It may be that the airflow when driving or through the hose is just enough to cool the coil? And then when it sits, the heat on top of the engine just soaks in? Anyway, I need an N80 valve, and the lesson is to test the valve under all conditions.

tester123

I am on my 4th one and I stopped checking/counting, just replace. Speaking of which, I have to do this tomorrow.