justinsbg

Honda has a service bulletin out explaining an issue with the Evap By-Pass Solenoid and the PCM. Here it is:

TECH TIPS
Honda — MIL on, DTC P1457 Logged in PCM Memory

Some 1998-2003 Honda models (complete list below) may turn on the MIL and log DTC P1457 in PCM memory. One likely cause for the evap code, reports Honda, is a shorted evap bypass solenoid valve. The short circuit is most likely due to salty water finding its way into the solenoid’s internal windings. The problem occurs almost exclusively in snowbelt areas of the country, says the carmaker, and in severe cases can take out the PCM, as well.

Start your diagnosis by hooking up a scanner to the DLC. If P1457 is the only code stored, put your hand on the solenoid valve and command it on and off with the bidirectional controls on the scan tool. If you don’t hear a click or feel a pulse from the valve when it’s exercised, the solenoid is shorted. Replace it with a better sealed unit, Part No. 17012-S01-A00.

Next, clear the code and command the new solenoid valve on and off with the scanner once again. If you still don’t hear a click or feel a pulse from the valve when it’s commanded with the tool, the old solenoid’s windings were probably corroded, taking out the PCM in the process. Replacing the module with Part No. 37820-P2P-A12 is the only remedy.

Vehicles that are prone to the evap trouble and can benefit from the improved solenoid valve are 1998-2000 Civics, 1998-2001 CR-V SUVs, 1998-2002 Accords, 1999-2003 Odyssey minivans, 2000-02 Insights, 2000-03 S2000 sports cars and 2003 Pilots.


If you are dealing with this issue and your PCM has been compromised, let me know. You don't need a new PCM!! I've also seen these items fail due to overfilling the tank and the valve getting saturated with gas causing the windings to short and the PCM to fail. I can give you another way to check these parts if you don't have access to a scan tool with bi-directional controls.

BuddyGuy

I think my 99 Civic has fallen victim to this...

Troubleshooting so far:

P1457 MIL thrown....
Tested Vent Shut Valve, doesn't hold vacuum when ignition on, and does when A4 connected to body ground. Looks good there.

Next, checked vacuum on the Purge Control Solenoid Valve with engine cold and idling, no vacuum.

Checked vacuum on the Purge Control Solenoid Valve with engine hot, in gear, with engine at 3,000rpm, no vacuum.

Checked for voltage around the 2P connector that plugs into the Purge Control Solenoid Valve, and I have VOLTAGE THERE ALL THE TIME WHEN THE IGNITION IS ON.

Replaced Purge Control Solenoid Valve (since I should have vacuum when doing the hot test).

MIL cleared, but comes back. Battery voltage still on 2P connector, however no vacuum (and the Purge Control Solenoid Valve is not opening), which is weird.

I have a feeling my ECM is screwed but I haven't checked the Bypass Solenoid Valve yet since I think I need to drop the fuel tank.

Do you think Honda would goodwill this? Especially a 99 with 241,000 km?

Any advice appreciated.

justinsbg

Alright, let me get you straight. All of the Evap solenoids are ground controlled, meaning that they all SHOULD have battery voltage until the PCM "activates" them by supplying a ground. That said, you won't see any vaccum on the purge valve until the PCM grounds it. Hook your meter up to the red/yellow wire on the purge valve (the ground side) with the engine running and whenever you see battery voltage switched to ground that means the purge is operating. The PCM duty cycles the ground so it will be switching on and off. You most likely have a failed by-pass solenoid/two-way valve assembly. Most of the time it's the two-way valve that failes but the by-pass solenoid usually has fuel in it and should be replaced to prevent future problems if it does in deed have fuel in it. Do you need instructions on how you can test the By-pass solenoid and two-way valve?

phootbag

Isn't it ironic that most of the failures of EVAP systems are with the government mandated devices used to determine if there is a malfunction/leak? What a joke.

BuddyGuy

According the official service manual, there are two wires in the Purge Solenoid connector, IG1 (blk/yel) and PCS (red/yel). IG1 appears to be wired into the main relay (which means that there will be 12V on that wire relative to body ground when the ignition is on), and PCS (red/yel) which is what the PCM latches to ground. I read 12V across IG1 (red probe) and PCS (black probe) with just the ignition on (both no engine running AND engine at a cold idle). To me, that means that the PCM is providing a ground, otherwise I would read a 0. Unless I've misunderstood how it works, either way I thought with 12V across the connector, the solenoid would open (either the old or new one), unless they are somehow blown by a screwy PCM.

If you have those instructions handy, it would be appreciated (I hope it doesn't involve dropping the tank for the test)...

justinsbg

The battery voltage you see on the red/yellow wire with the switch on means the PCM has not grounded the PCS. When the PCM grounds the PCS you will see near 0 volts on the red/yellow wire. You should always see battery voltage on the black/yellow wire (except when the switch is off). Take one meter lead and fix it to body ground and the other lead to the Red/Yellow wire. You should have battery voltage there until the PCM grounds it, at that point you'll see near 0 volts. I don't think you need to drop the tank. The two-way & by-pass are located on the left rear underside of the vehicle. If you're standing under the car facing the front they will be to the left of the gas tank towards the top. The two-way valve will have 3 vacuum hoses on it, 1 for the purge, 1 for the tank, and 1 for the FTP sensor. The by-pass solenoid is attached to it. Let me know if you find them and we can go from there.

BuddyGuy

I'll give it a go when I get home...

But I don't believe I'm seeing battery voltage on the PCS line... I measured voltage between IG1 and PCS (not IG1 and body and PCS and body, I stuck one probe into one pin of the connector, the other probe into the other pin of the connector)... and I got 12V... if I had 12V on PCS (measured against body ground) and 12V on IG1 (measued against body ground), wouldn't the voltage between IG1 relative to PCS be 0V? If there is 12V across the connector (relative to both pins on the connector), wouldn't that mean IG1 is 12V and PCS is ground?

I apologize in advance if I'm misunderstanding, but I'm just trying to wrap my head around auto electrical.

Thanks for the help again.

justinsbg

No that is not what that means. You're testing the potential across the connector terminals which at this point is battery voltage. Don't test across the connector. With the connector plugged up to the PCS, back probe the Red/Yellow wire and test that way. You should have battery voltage until the PCM grounds it.

BuddyGuy

Hmmm ok... I'll give that a go.

The reason why I went down the other route, is because according to the service manual (the actual Honda one), after I had tested the vacuum on the purge control solenoid when hot (and got no vacuum), the troubleshooting chart asks you to measure the potential across the connector. They imply that if there is no vacuum when the engine is hot (and in gear), and there is battery voltage across the connector, that the valve should be open (which its not)... the chart also implies that battery voltage should only be there when the engine is hot, and in gear... why else would they ask you to put the vehicle into gear and have it warm if there is 12V potential across the connector always even when its cold / engine not started

Here's the exerpt:

phootbag

The drawback to not using a factory scantool is that you must trust that the ECM is actually attempting to activate the solenoid. Other than seeing a ground path you have no way of knowing. Sure, the book may be able to tell you when the solenoid SHOULD be activated but without the scantool to activate the solenoid manually through the ECM you have no way of knowing if the ECM is actually providing that ground.

So, the question becomes, is the ground circuit within the ECM faulty? Or, is the wire between the ECM ground and the PCS open? Or, is the ECM even trying to ground the solenoid at all?

justinsbg

We are a Honda specialty shop so we literally have at least a hundred manuals, I personally rarely ever use a troubleshooting tree provided by Honda. There are much better, more efficient ways of diagnosing most systems. I'm trying to simplify things for you. I've spent many hours diagnosing and teaching diagnosis of this particular system. Trust me when I tell you that there will always be battery voltage on the solenoid until it is grounded by the PCM. The PCM should provide ground for the solenoid after the engine coolant temp is above 154 degrees and the vehicle speed is above 0 mph. You won't have vaccum on the purge hose until the Purge solenoid is grounded. With the front end raised and the vehicle in gear with the other criterea met, you should see the battery voltage pull to ground. When that happens the Purge should start duty cycling and you should have vaccum on the hose that runs from the purge solenoid to the canister. Forget the trouble tree for a bit. I've never seen failed PCM evap circuit in this particular model, but anything is possible.
If you don't have a scan tool to operate the solenoid via bi-directional control, I can explain how to use your multimeter as a bi-directional control. Doing that you will be able to open & close the solenoid, and at the same time see the amperage the solenoid is drawing. If you would like for me to explain this method to you I would be happy to do it. I would start with the easier component to test and work your way back towards the two-way valve & by-pass solenoid.

BuddyGuy

That is a good point, and I thought perhaps there is a ground short in the PCS line (for example, the PCS wire is touching the body somewhere along the way to the PCM), but I unplugged the A harness from the PCM, and checked for continuity between the PCS line (at the connector) and body ground and found none (aka infinite resistance).

BuddyGuy

I'll have to pick up a back probe set (since my meter didn't come with one), but I see where you are going with this..

With the connector hoooked up to the solenoid, I should see the battery voltage from IG1 on the PCS side (after it goes through the solenoid), and it'll pull to ground once the conditions are met. Measuring each terminal against body ground (with the connector unplugged) doesn't mean anything... I apologize for being a tool, but I think I've figured it out.

I'm interested in the bi-directional control though, and using the meter to do it. Do I need to hoist up the car to get to the 2-way/bypass solenoid, or will a regular jack + stands be enough?

justinsbg

Exactly, you got it. If you don't have a back probe set you can use a paper clip or someting of the sort. I don't think you have to drop the tank, but I was looking in the factory manual for the location of the valve and it says you need to remove the fuel tank to test it. I personally have never done any evap work on this vehicle. You'll just have to look under the car and see if you can locate it. Look around the gas tank and hopefully you can get to it without too much trouble. I've worked on a lot of evap systems on many different Honda cars and I've never had to drop the tank, that's rediculous. Hopefully the Purge Solenoid is the problem and you won't have to drop the tank. Now, for the Bi-directonal test. You must be careful in placement of your leads as well as how you have your meter set or you'll blow a fuse or worse...your meter!! Here it is:

The ignition switch should be on and the connector plugged up

1). Set your meter to the HIGH amp scale. For example I have a Fluke meter and I put my meter positve lead into the 10amp port. Keep your ground meter lead in the normal spot.

2). Back probe the red/yellow wire with your positive lead, and momentarily ground the negative lead. The solenoid should activate. You should also see the amp draw on your meter. What you're basically doing is taking the place of the PCM. You're duty cycling the solenoid with your meter. Don't keep it grounded for more than 5 or 10 seconds. A good working solenoid will draw around 0.350-0.400 amps. I would ground it about 10 or 15 times in a row and note the amp draw, if it increases/decreases substantially it may need replacement.

What I would also do is get the engine hot and jack the front end up. Put it in gear and pull the hose off the purge that runs to the canister. Back probe the red/yellow wire with one meter lead and ground the other to body somewhere. Check for vaccum on that hose when you see the solenoid pull to ground by the PCM. I'm starting to see quite a few purge solenoids fail, so hopefully that's the problem. Let me know how it goes.

justinsbg

I definitely get your point, but I always like to use the "most likely" method of diagnosis. A lot of times experience is the best teacher, especially in this business. If you work on Hondas often then you can ask yourself "how often do I see wiring problems on this model?". It's not likely that there is a wiring problem, but anything is posible. I always like to start with diagnosing the most likely cause of a problem then work my way out. It's very convienent to have a factory scan tool to aid in diagnosis, but in this case it's not necessary. The Purge should be working when the criterea are met, if not then we would figure out why.

BuddyGuy

Sounds good... should I do the bidirectional test with the meter on the purge solenoid first (I really hope it isn't broken, since I've just replaced it with a brand new Honda OEM part) before doing the hot engine/jack front end up test?

When I tested the original Purge Solenoid, I ran a hose from the purge solenoid into the vehicle, and hooked a vacuum gauge to that, and even with the engine hot, and in gear and driving around, I didn't get any reading on the vacuum gauge, that's why I had replaced it.

Also, with the meter test, it won't harm the PCM right? I mean, since the PCS line is still hooked into A3 of the PCM...

justinsbg

Forgive me, I forgot you already replaced the solenoid. I wouldn't think your brand new part is bad. I would do the test you did initially, the only difference is have your meter back probing the red/yellow wire. Make sure that the PCM is grounding the solenoid before you check for vaccum on the hose. With the engine warm, the front end raised, and in gear raise the rpm's a little so the vehicle speed will increase. See if you can manipulate the PCM into grounding the Purge. You can use the Bi-directional test on the by-pass solenoid and CVS valve if you end up having to go there.

BuddyGuy

Update: I did the bi-directional test on the Purge solenoid, and I got 0.334A, with a click in the solenoid when I grounded the other lead (didn't test to see if the valve opened)... I also hooked up the old solenoid (which didn't read any vacuum during the initial road test), and it also gave me a similar current reading with a similar click... I'll probably do the "in-gear"/running test tomorrow. I also did a similar test a while ago with the CVSV (canister vent shut valve), by grounding the A6 pin at the PCM, and I also got a click, and it held vacuum, so I don't believe its the CVS.

I have a feeling something is screwy with the ECM, or perhaps the by-pass solenoid is internally shorted, and is causing problems downstream.

justinsbg

Good deal, looks like we're narrowing it down. When you do the "in-gear" test we'll know a little more, and probably determine where you need to go next.

BuddyGuy

I just did the "in-gear" test, with it in 2nd gear, running to about 4k rpm / 60kph, and my back-probed PCS line stayed more or less within 12V +/- 1.5V. I repeated the test 3 times just to make sure, but I didn't at any time see it drop below 10V.

The rad fan did cycle a few times, just to note.

BuddyGuy

Could it be a shorted bypass valve (as per the above TSB) causing problems in the PCM's ground circuit (which would explain why the PCS is not opening)? Or am I SOL with this PCM?

justinsbg

Usually the failed By-pass solenoid burns it's ground circuit in the PCM, so I don't think the PCS would be affected by it. I don't think the criteria is being met for the PCM to duty cycle the PCS. Just because the book tells you the certain criteria it needs to run, doesn't mean that it will run under those conditions. I would take some an extended test lead, hook up to the red/yellow wire and run them inside the car, hook my meter up inside the car and drive it around for a day or 2. Watch the meter and determine if it ever gets grounded by the PCM. Do you have any other stored codes in the PCM besides the p1457?

BuddyGuy

Hmmm, I'll have to buy a set of extended test leads..

Nope.. only P1457.

rlim59

i sent this as a private message but figure id put on here as well

i dont drive a honda anymore but this is for my eldery moms car. she has a 2001 honda accord ex 4 cyl and this is what happened.

the CEL came on and pulled the code at autozone. the gas cap is tight. the CEL was on when she drove to church. 3 hours later when she tried to start the engine there was no CEL but no sound. the car wouldnt start. then she heard a noise like a tape was moving or some sort of motor sound. click click. she tried to start again and it was fine with no cel.

the car currently has no cel light on. what is this issue?

thanks ahead of time!

TucsonJDMAccord

i have been having this p1457 problem as well. i tightened the gas cap drove for 50 miles, still the cel is on and it is still throwing the same code.