This code identification is "EVAP canister purge control valve solenoid valve or circuit fault,"

I back probe the EVAP solenoid terminal while the engine was running and got 12V. I removed the solenoid and followed the service manual procedure to check the solenoid which checked out good. I disconnected the ECM terminal and check the ground side of the solenoid wire for continuity and leakage to ground and it check out good. So I replaced the ECM with a used one and the code returned again. Could the solenoid trigger the code even if the solenoid checks out good?

 

Do you mean P0443? That code applies to both the EVAP canister purge control valve and the purge control solenoid valve. Those are two separate parts. If the solenoid valve tested good, you have to also check the purge control valve, which is the part that looks like a black cylinder with a hat on it. See page EC-233 in the FSM.

 

Yes, the code should be P0443. I also tested the black plastic EVAP canister purge control valve according to the procedure in the FSM and it tested good. But, I replaced this valve because the old valve opened at a vacuum value below the 100mm Hg as specified in the FSM. Word to others, the new valve opened at an even lower vacuum. Therefore, if you test the valve and it opens at less than 150 mm Hg, don't change out the valve. Also, according to the recommendation in the technical bulletin, I also replaced the EVAP pressure sensor at the left rear of the car. Now that I replaced good parts, I would like to pin point the faulty part before I change out any more.

In the FSM for this DTC, in the table listing possible malfunctions: "malfunction is detected when...." column, Improper voltage signal is sent to ECM through EVAP canister control solenoid valve. Do you know how this voltage can be check?

This problem has been with me for a couple of months and I tested more than I would like, any suggestions are appreciated.

Thanks,

 

By backprobing the wire where it enters the ECM connector, on the back of the ECM. But I don't know what "improper" means in this case, because I don't know what it's expecting to see. It might be looking for a pulse indicating that the solenoid has opened and closed when commanded. A CONSULT system might also be able to display it.

I would like to be able to say "I'll measure it on my car and see what I get" but getting to a particular wire on that big connector is so hard, I can't promise anything.

 

I don't know what the improper voltage is for this and not knowing when the ECM runs the EVAP diagnostic, backing probing at the ECM may not be very helpful. I agree that you may be able to get reliable information with a consult but I don't have one. So, without a consult, do you think replacing the solenoid is reasonable choice?

 

I just measured the voltage drop across the EVAP solenoid by backprobing the two wires entering the solenoid's connector. With key on engine off, there's battery voltage on both wires. Same when the car is at idle (well, charging system voltage on both wires). Revving the engine up above 2,000 rpm and keeping it there for a minute or so, the ECM grounds the circuit and the solenoid opens (or closes, I don't know which) to actuate the EVAP purge control valve and draw vapor from the EVAP canister. The voltage drop across the solenoid then approaches the charging system voltage, and the voltage on the wire to the ECM should be close to zero. When the engine rpm drops below 2,000 rpm, the ECM will break the circuit and the voltage on the wire to the ECM will go back up to charging system voltage.

If you don't see this, the solenoid coil could be open (zero voltage on the wire to the ECM all the time), shorted (presumably the fuse would blow and you'd have no voltage on the red wire to the solenoid), or there could be high resistance in the circuit between the battery and the solenoid (you'd then measure less than full voltage on the red wire at > 2,000 rpm) or between the solenoid and the ECM (you'd measure more than 0.2 or 0.3 V on the wire to the ECM, at > 2,000 rpm). Or you could have high resistance between the ECM ground and the negative post of the battery.

 

The ECM actuates the EVAP solenoid when engine rpm is above 2,000 and steady. It might also do it when the rpm is lower than 2,000 but the car is moving. I don't think the EVAP monitor running or not has anything to do with the voltages you measure across the solenoid or at pin 114 of the ECM - the EVAP solenoid is opening and closing regardless of whether the EVAP monitor is running. Anyway it's probably the continuous component monitor that detects the wrong voltage on pin 114 of the ECM. The EVAP monitor runs only once per trip, and might not run at all once the DTC is set.

I would measure the voltage across the solenoid with the engine warmed up and idling above 2,000 rpm, and then watch what happens as you rev it up and down across 2,000 rpm. That should give you a clue as to what's going on.

 

I will check out the voltages this weekend and keep you posted.

Again, Thanks

 

I checked the voltage on the ground wire at the solenoid, and it's 315 mV when the engine is warmed up and idling above 2,000 rpm. Below 2,000 rpm, it will be close to the charging system voltage. Apparently there's about a 300 mV drop across the ECM connector and the transistor inside the ECM that's switching the circuit to ground.

 

I got the same results as you did:
I back probed the purge control solenoid terminal and hooked up two volt meters. Both of the meter’s common probes were clipped to the battery's negative terminal. One meter's positive probe was clipped to the Red w/yellow stripe wire and the other meter's probe to the Blue w/yellow stripe. At idle both meter read 13.69V. After warming up the engine and revving the engine to at least 1,500 RPM the red side voltage dropped slightly but otherwise remain constant at 13.69V but the voltage at on the blue side dropped and stayed steady at 0.25V. Cycling the engines rpm up over the 1,500 RPM resulted in the same readings each time.
The next thing I did was hook up a vacuum gage to the purge line between the canister and purge control valve (black hat looking vacuum valve). I revved the engine to 1,500 rpm and held the rpm constant. Temporary (less than a second) vacuum was observed and ceased almost immediately. This would occur every time the engine was revved to and held above 1,500 rpm.
I removed the vacuum gage and hooked it up to the signal vacuum line from the solenoid. I followed the same process above and the vacuum would hold constant while the engine speed was held at 1,500rpm or above. I don’t know why the vacuum was not constant in the above test. My guess is the purge volume control vale could be stuck in a loosely closed position which leaves very little vacuum available to purge the canister. If this is the case I should get DTC 1008 or P1445. The only thing I can think of is the pressure sensor sees not vacuum after energizing the purge solenoid and the ECM is code to return DTC 0807 or P0443. I tested the volume control valve according to the FSM for DTC1008 or P1445 because the only thing between the purge control valve and the intake manifold is the volume control valve. All check out “OK”.
I spent more time searching the web and found out that the 0807 or P0443 code has lead many people to replace many good components. I think this is a general code and not specific to the EVAP solenoid and its circuit. Here is a list of components that I believe could trigger this code: Gas cap, canister, ECM, and pressure sensor. This is one of the most reliable link I found during my searches is http://zilvia.net/f/engine-tech/2560...e-intense.html. If the post is not available and you would like to read it, I can send you a copy. There is also a technical bulletin that recommends replacing the pressure sensor for this code which I already replaced.

 

It looks to me like the EVAP solenoid is confirmed good by your diagnostics. But it seems like the purge control valve (the black hat valve) might be failing. Did you test that valve off the car? Maybe it fails intermittently. P0443 covers it as well as the solenoid valve, along with the pressure sensor you replaced.

 

I tested my "OLD" purge control valve (Black Hat) and the valve opened at -50 mmHG. But according to the FSM, it should open between -100 to -150 mmHg so I replaced it with a new one which opens at less than -20 mmHG. Both valves open and close with no vacuum loss when tested outside of the car. Do you think the code 0807 is limited to the purge control circuit, solenoid, and valve?

Today, I checked and blew out the vacuum line between the purge valve and the canister hoping to find some charcoal debris but the line was clean. I also applied presure (about 6 PIS) and vacuum (10" Hg) to the line and did not detect any leakage (held for at least 30 seconds).

 

When you clear the code, does it get set again immediately? Does the freeze frame data always look the same? Wondering if the fault is intermittent or constant.

When all else fails, check grounds. The solenoid driver circuit's ground is one of the ECM grounds. I don't know where it is, though.The monitor is looking at the voltage on the ECM pin relative to the ECM ground. That voltage could be different than the voltage measured relative to battery negative, if there's corrosion or wire breakage on the ECM ground. But it seems like you would've measured a higher-than-normal voltage instead of what you got.

 

The code never appeared on the first trip (after reset). After resetting the code, the code reappears between the second and the four trips. The code mostly after the second trip. I’m not sure what you mean by “freeze frame data” please enlighten me.
Would resistance between ECM chassis ground to battery terminal give me an idea of how good the ECM ground is?

 

The ECM stores a handful of parameters when it sets a DTC. Engine load, vehicle speed, fuel trims, and a few other things I can't remember. You can retrieve the freeze frame data with a scan tool, but not with a code reader. If the freeze frame data looks the same every time the DTC gets set, the fault isn't likely to be intermittent. If it looks different, well that doesn't really say it is intermittent.

Measuring the resistance is not the best way to determine if a circuit has high resistance, on a car anyway. The best way is to measure the voltage drop when the circuit is loaded. You can measure it when the ECM has grounded the solenoid. Anything above 200 mV between the ECM ground pin and the chassis ground is an indication of high resistance. But whether that would trigger the code is hard to say. It won't if it's not there, for sure.

There's a little book by Daniel Sullivan called Fundamental Electrical Troubleshooting that explains how to do voltage drop tests. Somewhere in there he says "when stumped, check grounds." There's also a good video on YouTube by ScannerDanner, a vocational school teacher, that explains solenoid driver circuits in some detail. I don't recall the title but I think it had EVAP solenoid in it. All his videos are great. He sells a "book" which is really a big PowerPoint presentation, that's also really good. End of sales pitch.

 

Come to think of it I don't think there's anything wrong with the ground, since you measured a low voltage out of the solenoid. Anyway I looked at the FSM and the ECM is grounded through the engine grounds in front of the intake manifold. I thought the ECM ground was somewhere in the vicinity of the dash, but it isn't.

 

I will check out the ground points. Yesterday, I started to check each and every component according to the FSM for the second time since encountering code DTC 0807 problem. In addition to checking them on the car, I also check them off the car. For the lines and canister, I applied both vacuum (-200mm - minimum and pressure (up to 0.5pis). I applied only pressure to the tank as I don’t have a vacuum pump to apply vacuum. These are the ones I checked so far: 1. Pressure sensor, canister vent valve, canister, vacuum cut valve, vacuum cut valve bypass valve, purge volume control valve and gas tank. They all checked out good. I also cleaned and blew out each component. As you can see I am determined to figure this problem out….hopefully soon. I will keep you posted.

 

Finally, I solved the problem but I am not 100% sure what was the issue. I think this 0807 DTC is a code that can be recorded not only by faults in the purge control solenoid valve or purge control valve circuit but by faults elsewhere.
I concluded that based on the observation (see above posts) during the test of the purge control solenoid valve and purge control valve system that the very short presence of vacuum was caused by a semi-blocked purge volume control valve. Although the valve tested “good” following the FSM test procedure, you should also test the valve for proper air flow.
After resetting the ECM and not DTC, I ran the purge control test procedure shown on the above post; I get vacuum in the line following grounding of the purge control solenoid which convinces me that the purge volume control valve was blocked. Thanks, ATTappman for all your help!!

 

That's good to know. I guess this particular way of failing wasn't anticipated by the developers of the ECM code, so it got somewhat misidentified.

I wanted to do the same vacuum test you described, but the hoses on my purge control valve look like they'll disintegrate if I try to take them off.

What brand of vacuum gauge did you use, and what fittings do you have? I've got a parts store Innova, but it doesn't come with enough fittings to make it useful. I wish I knew of a vacuum gauge set with a whole bunch of different good quality brass fittings.

 

I bought a cheap vacuum pump from Harbor Freight and a cheap pressure/vacuum gage on line and calibrated them by creating vacuum with a column of water. I only calibrate them at the low end to about 5” Hg or about 5 feet H2O with a column of water. To my surprise, for a cheap pump, it was accurate enough for the EVAP testing. Unfortunately, good brass fitting that allows for various size tubing is hard to come by. I used the plastic ones from Autozone and it is not the best but does the trick.

 

Never thought of looking for the fittings at Autozone. Over by where they have fuel and vacuum hoses I guess. Thanks for the tip.

 

You may want to try a plumbing supply house which has brass barbed fitting.

Good Luck

 

I had this fault a fewmonths back, checked out a few components acording to the FSM but only found my gas cap wasn't creating a complete seal (aftermarket cap from autozone because my factory cap failed emissions). Thought for sure that was what was setting the code but it came back pretty quick. My purge volume control valve was working OK but I took it off and opened it and found the inside to be extremely dirty. Replaced it with one at the junkyard that was clean and worked and haven't had the code since.