My 99 Integra is giving me a 1456 code. There are no leaks and all valves actuate and hold vacuum. By monitoring my FTP, I have determined that the bypass solenoid is not opening while driving (unless I ground the wire on the ECM to make it open, then the FTP voltage changes. A bad ECM is the only reason I can think of that this thing is not opening. Is there a way to test the ECM?

I should include, that I just replaced the bypass solenoid due to it leaking vacuum when I first tested it. I have heard that these can fry the ECM when they go. Mine only leaked though. I could still hear it click when I activated it (so it wasn't burnt up).

 

Can you borrow a known working ECU/ECM to test in your car?

My guess is it is the ECU/ECM is bad.

What is FTP?94

 

I don't know of any way to borrow an ECM. By FTP, I am referring to the Fuel Tank Pressure Sensor. There must be some way to check if this thing is working. Half the trouble is that I am not 100% sure of the conditions where the bypass valve would open.

My hunch is that if the purge is opening (which it is), the bypass should open at the same time so the engine can pull vacuum on the tank.

 

OIC, FTPS, should have known.

How is your gas tank cap, is it in good working order? 94

 

The system holds vacuum (the voltage remains constant on the FTPS). So, I would say the cap is good.

 

Well, I went ahead and just ordered a used ECM. I was hoping that someone on here would know how to diagnose these kinds of problems.

 

AFAIK the only way to test an ECU is to see if the signals going in are correct and the ECU is not responding correctly. It's kind of an "everything else failed" sort of thing. Small comfort: if you don't wind up needing the ECU you just bought you'll hopefully be able to sell it for what you paid for it.

 

Over the years I have seen more bastard problems caused by poor grounds than any other single cause. My default starting point has become checking grounds first. Look for white crud, rust, frayed wires, etc. You might even do a continuity check with an ohm meter between battery ground and ECM ground. After all, this solenoid is activated by pulsing a ground.

Mike

 

I don't think I have any corroded grounds, but I will check the resistance like you suggested to be sure. Wouldn't a bad ECM ground be causing other more serious problems?

 

I live in a serious rust belt, so I see bad grounds all the time just from the salt they put on the roads. At least up here, I've never seen anything external CAUSING a bad ground.

Mike

 

It was the ECM. Problem solved.