Check engine light came on after about 10 minutes. Had error code 46 on the diagnostics. Changed out the charge relief valve and the solenoid ($228) per the FSM instructions, and guess what...I still have error code 46. INT WTF!!!! Solenoid is getting power, according to FSM procedure the solenoid/valve is defective, but I just replaced them. FSM doesn't have any other info on this. Anyone seen this before?

 

did you reset the ecu??

 

Yes. Same code came back.

 

I've had to do the procedure two or three times (bad IAT) before the ECU would finally reset and the CEL go out. Not sure why.

 

Check the wiring continuity for the solenoid plug (on the harness side).

 

Followed the FSM, side a of the solenoid plug has +12v with the key on. Side B of the solenoid plug has continuity to 4S on the ECU plug. The coil on the solenoid measures good (it's brand new). Possible the ECU is bad?

 

how did you reset the ecu?

take of negative term. on battery, depress foot on brake for 30 seconds? hook negative term back to battery start car?

 

Yes I did.

Sgtblue above mentioned he had to do this several times, so I tried that too. He also mentione a "bad IAT". WHat is that?

 

I just noticed something on twisted7's reply. He says hold the brake for 30 seconds....I don't think the procedure I have says to hold the brake, just to apply it. ANyone know more about this?

 

I've heard 20 sec myself. As after as I can tell, discharging the system happens quite quickly (thus why just applying it may be good enough) but people hold it for a while just to be sure.

 

IAT = Intake Air Thermosensor, it's under the UIM (FSM page F-183). I'm assuming that was just the code he was trying to clear.

 

Correct.

 

So a bad IAT will also cause a code 46?

 

I don't think so: Sgtblue was just saying that he had to reset the ECU several times to clear his IAT code.

 

OH, I got ya. I was going to say, the FSM say an IAT is code 10 or 11 and I don't have either of those. I'll try the 30 sec brake thing and see if that does it.

 

Correct. IAT is code 11. I didn't mean to confuse. I was just explaining why I had to clear the CEL.
Like you, I was pretty certain the the connection was good and in my case the IAT sensor was new. So when it didn't clear the first time, I repeated the procedure. On the second or third attempt, it finally cleared properly. I don't know why, but that was about two years ago and everything has been OK since.

 

Need a little more clarification on this. Did you drive the car between trying to clear the codes or did you just repeat the process without driving the car?

 

Just repeated the procedure listed at the top of the page F-66 in the FSM: Unhooked neg. battery for 20 sec., pressed brake pedal, started car. Waited a moment and CEL was still on. Unhook neg. battery for 20 more sec.....press brake. Hook battery, start car, obsevered CEL and IIRC, repeated once more.
Have you double checked the plug/connection for the solenoid as Mahjik suggested?

 

I did. I checked for voltage at the solenoid connector, checked continuity between the connector and the ecu, checked for voltage at the ecu with the solenoid installed - everything indicates the solenoid is good. I applied vacuum to the relief valve and it is definitely activating. I just realized though, I never checked vacuum at the relief valve with the engine running. Gonna go try that now.

 

And the saga continues......

Good vacuum at the relief valve.

I got the code 46 to clear, but when I did I got a code 40 that would not clear. Then I drove the car and when I got back code 46 had returned. Is it possible that I have a bad purge control solenoid and that is somehow causing the charge relief to malfunction? I don't know how these 2 relate to each other yet, but I'm sure I'll learn.

 

Many solenoids share grounds. I haven't looked at the wiring diagram, but its possible that those two share the same ground. How old is your wiring harness?

 

[QUOTE= How old is your wiring harness?[/QUOTE]


It's a 93 FD, guess the harness is 14 years old.

I don't understand the statement you made concerning the solenoids sharing a ground. All solenoids are supplied +12v from the main relay with the ignition switch ON and are actuated by ground signals supplied by the ECU when appropriate conditions are met.

Code 40 pertains to the purge control valve. The purge control solenoid gets a control signal (ground) via pin 3H on the ECU. This pin should decrease to 4-10 vdc between 1500-3300 rpm

Code 46 pertains to the charge relief valve. The charge relief solenoid gets a control signal (ground) via pin 4S on the ECU. This pin should go low (<1v dc) when engine RPM is between 4000-5500 for more than 8 sec or above 5500 for 4 sec.

I don't think these 2 codes are related, but I don't know.

Hey guys, I really appreciate all the help on this.

 

Maybe ground is not the correct term (I'm not an electrician nor do I pretend to be). If you look at the wiring diagram, each solenoids has two wires running to it. One is unique, the one you mentioned at the ECU side, and one is shared.

In looking at the diagram, I'm not sure that there could be a problem with the other wire without causing a few more codes than what you are seeing. I would still suspect something with the wiring harness might be causing your issues if the codes are intermittent (and you have verified the harness connector continuity and the sensors' continuity).

 

I've checked the wiring, don't find any problems

 

There is obviously something wrong with the circuit or else you wouldn't be getting the codes. The ECU triggers that code when it doesn't have the proper resistance in the line.

It's possible that you have a damaged wire that maybe losses continuity once driving and moves a little. Either way, since you don't have more codes, I would suggest its something with the unique wire from the ECU to the solenoid. Whether it's the ECU, connectors (ECU or solenoid side), wiring or solenoid (doubtful since you just replaced it, but its still part of the equation) is something you'll have to track down.