Diagnostic Scanner Codes...

[JW in Ohio]

My "service engine soon" has been on in my 98 ZX2. Took it into Auto Zone and it came back with two codes.
1. P0171 which is described as "Bank 1 system too lean" The guys there said it could be the O2 sensor, but you can't tell more without further testing equipment.
2. P1451 which is "Evap Emission Control System Vent Control Valve curcuit" (Sounds expensive!). They weren't sure what this, but my web reading indicates it is something about a sensor on the charcoal canister for the gas vapors.

Does anyone have experience with either of these faults? Anyone know enough to make a good guess? The car runs fine now that I replaced the CCRM (thanks paul78zephyr), but the service light keeps reminding me something is not right.

Jim

[Markb873]

Possibly your canister vent valve is stuck open leaning out the fuel mixture. P1451 trips when the signal moves outside the minimum or maximum allowable calibrated parameters for a specified canister vent duty cycle by PCM command. So a bad solenoid or bad wiring. P0171 trips when the MAF Sensor is dirty or faulty or if there is a vacuum leak downstream of the MAF sensor.

Most likely the MAF is fine and the solenoid is your real problem because the canister vents into the intake downstream of the MAF which would lean it out if it's stuck open.

If the solenoid is getting 12v and the valve is open it's a bad solenoid.

Hope this Helps!

[AltecZX2]

never heared of canister vents

[Markb873]

Originally Posted by AltecZX2

never heared of canister vents

Vapor Trapped in the gas tank is vented through two valves in the top of the tank. The vapor is routed through vapor tubes to the carbon canister. The canister holds fuel vapor. The Vent is the hole the vapor goes through, controlled by the Evaporative Emissions(EVAP) Canister Vent Solenoid(CANVNT). The canister is purged when the engine is at operating temp and off idle. It's Component C442 on the Ford Wiring diagram. Behind the left rear tire under the bumper cover. I've never seen it but I trust Ford that it's there. While were on the subject of canister vents, the context i used it in stated "canister" as a noun and "vents" as a verb.

[JW in Ohio]

Thanks for the info Markb. I have examined the canister and what I think is the solenoid. How do you tell if the valve is open? And when checking for 12v at the solenoid, it sounds like I need to be at higher than idle engine speed? Anyone have more info?

Thanks,
JW

[Markb873]

I apologise. I noticed an dyslexia because of my error! The solonoid should open the valve not close it. Otherwise you'd have a dead battery quickly! Checking for 12v verifys the circuit integrity and yes it does have to be off Idle. You also can simply check for continuity. If the circuit is intact then you can assume the solinoid, or the PCM. So theoredically there should be no voltage with the ingition on, engine off.

The OBDII website says this:
A code P1451 may mean that one or more of the following has happened:

VPWR circuit open
Damaged canister vent solenoid
Canister vent solenoid circuit open or shorted to ground, power, etc.
Damaged Powertrain Control Module (PCM)

The only thing that seems to make sense is the purge valve is stuck open because the solenoid is stuck . That would be the only way to get the p0171 unless it's a unrelated leak in the intake line after the MAF. I would say find out whats wrong with that solinoid before you try to fix the other code. And hopefully your mixture won't be so lean.

Hope this gets you one step closer!

[JW in Ohio]

A quick follow-up and a public thanks to Markb873. I replaced the solenoid with a new one from the Ford dealer for around $50 and we are good as new. Service light is no longer on, and car runs great--much smoother at idle. Thanks again.

[catlettdale]

i am having a few issues myslef , I bought the car a few days ago , its a 2001 zx2, well after I bought the car later that night a code popped up ( engine light ) so I go to get it checked also , i dont remeber the exact number but it was the system is to lean also- per bank 1 , so we ended up testing it further and it said there was a vaccum leak - by the way the only reason I even messed with the light was it was dying at stop ights and it also dies when i slow down.. only when i slow though, rpms could be at 3500 and then when I slow it just bottoms out and the thing is dead.. anyway so i changed the vacum theat goes to the pcv valve and leads around to the intake ... well when I came home the car dies like 4 different times when coming to a stop... i think a normal idle is what like a little over 1000 and mine doesnt idle there , i mean sometimes it does but most of the time not , so theres other issues also, wehn hitting high rpms this thing has a damn battery light that comes on and goes off several times in succesion ... so i changed the terminals where there was corriosion and guess what it still does it , changed that vacuum i mention , still dies , hmmm i also changed the plugs in it and pcv valve ... could this be that it needs an aternator , im sure it does even though it test fine , and could the dying be its a idle control module or maf sensor .. im sure it prolly a sensor issue but which one of the damn thigs lol ... i would appreciate if someone had any insite to this , also you can email me at catlettdale@yahoo i check that more often .. thanks

[JW in Ohio]

Catlettdale:

It sounds like you have several things at once, as I did. As stated in my earlier post, I had 2 scanner codes show up. One was for the charcoal emission canister solinoid. I changed that and that code disappeared. The other one was for a lean intake. Could have been several things, so instead of changing parts at random I paid $70 or $80 to a dealer for a detailed analysis. They said it was the MAF (mass airflow sensor) and wanted $250 for a new one. I declined and got a remanufactured one from a parts store for $80, but a few days later the service light came back on. Back to the dealer, they replaced the PCV valve and that finally fixed it, but they still said it was good to replace the MAF. Yeah, right! Runs like a champ ever since. My advice is: if the basics don't fix it, it is worth taking to a dealer for a detailed computer scan. I hate to pay a dealer for stuff, but I was beyond my abilities and didn't have any better options. Good luck.