Hi, first time post and in need of some help.


I have a P1457 code on a 1997 Civic EX coupe (D16Y8).


I've followed the flow diagram in the manual.


1. Disconnected vacuum hose from 3 way valve, disconnected canister shut valve. No vacuum
2. A29 to ground. Vacuum
3. Disconnected vacuum hose from canister. 3000rpm I have vacuum
4. Disconnected 2p connector from purge solenoid. 3000rpm I have vacuum.


The vacuum hoses are routed properly and the purge solenoid is good (I tested).


I have 14v+ between the 2p black/yellow and ground when running (no matter the rpms). 0.3v between 2p red/yellow and ground when running. I feel like it's a wiring issue, but the flow diagram ends with replace the purge solenoid that I know is good.


Any help is appreciated. Thanks.

 

Has gas cap been tested?

 

Gas cap has been replaced. I'm wondering why the blk/yel has voltage across all rpms? Somehow the purge solenoid must get a signal to open at higher rpms.

 

How do you know the purge solenoid is good?

Are any other codes thrown?

Aside from P1457, does the car have any problems whatsoever? Any idle problems?

 

The solenoid opens when tested with 12v. I've also tested with a spare solenoid. There are no other codes or idle issues. Only P1457.

 

Pulled vacuum with pump and vacuum did not hold?


Pulled vacuum with pump and vacuum held?

 

Correct. No vacuum with pump on #1. Vacuum on #2.

 

When ECU is reset, P1457 returns immediately or under certain conditions?

 

It doesn't return automatically. After about 35 miles and a stop/restart it reappears.

 

In first vacuum pump test, did you remove shut valve from canister?

 

Yep, the shut valve was removed in test #1.

 

When vacuum is held during a test, how long do you monitor? How much vacuum do you pull on the gauge and does it change during the test?

 

20 seconds or so. I pulled about 20 inHg with no vacuum loss.

 

20" Hg is not a deep vacuum. Perhaps you need to pull a deep vacuum (e.g., 27" Hg or more) and test whether it holds or not after 15 minutes.

You also may want to compare vacuum at the IM versus what you read at the EVAP hoses with engine at 3K rpm.

 

My mittyvac only pulls 30in on the gauge. What do you consider deep? Appreciate the help!

 

I edited my last post. Deep vacuum is generally between 27 and 30" Hg. For the pump tests, also prolong the time you monitor loss of vacuum to 15 min. It's best to assume at this point that there's a small vacuum leak.

 

How much vacuum does the engine pull at 3K rpm from the EVAP hoses?

 

I'll give that a shot tomorrow. What is IM? Intake manifold? Where do I test that?

 

IM = intake manifold

All vacuum produced by the engine comes from hoses attached to the IM. I'd be curious to compare the vacuum readings at the EVAP hoses to the reading directly at the IM, with the EVAP hose disconnected and the IM nipple blocked.

The cruise control nipple on the IM would be a good place to measure IM vacuum (with engine held at 3K rpm like the EVAP test).

 

Got it. So I still question how the purge solenoid works. Shouldn't it open at a given rpm? I have constant voltage from idle to 5000rpm at the blk/yel 2p connector. Seems backwards to me that the blk wire is hot. Shouldn't the red/yel have voltage?

 

The Blk/Yel wire supplies constant battery voltage to the solenoid via fuse 15.

The Red/Yel wire is ground for the purge solenoid and runs to the ECU. The ECU controls the solenoid by controlling ground, not voltage.

 

I need some help understanding. How does the purge solenoid open with respect to wiring and rpms?

 

 

Thanks. So the red/yel from the ECU goes to ground above 154F or with a/c on to open the solenoid? Wondering why I don't have continuity between red/yel and ground above 154F? ...I'm electrically illiterate.

 

From my understanding, the first issue appeared at this test step:



It seems that you should not have detected vacuum, but you did.

In addition, if there was a short in the solenoid ground wire, unplugging the purge solenoid connector should have eliminated vacuum in the next test, but it did not. It seems like the purge valve is stuck open.