No check engine light 90 Legacy

[GregS]

I posted a problem a couple weeks ago with a 90 Legecy. It was dying after 30 minutes of running and will than restart after 45 minutes consistantly. I had a code 22 and 35. Replaced both related sensors and everything seemed fine. 400 miles later, it happened again. This time, I tried to check codes on the ECU, but the check engine light was not working. with the key in the ON position, the light will flicker on very lightly for a couple seconds, and I can hear a clicking behind the dash like a relay coming in and out as the CEL goes off and on. I know there are a few relays back in that area, but are any related to the ignition system? Or is there something in the ECU that could click? I had the same reaction when I plugged the connecter up to pull the codes. After the 45 minute wait time, when the car would fire up again, the check engine light work as it should, and there are no codes. Does it sound like a possible bad ECU?

[subeman90]

for the light to flicker and the fans to cycle on and off there is a test connector that is still hooked up that is normally unhooked. Look under the drives side dash for a green conncetor and a black one (I believe they are single wire connectors) and if you find them together unhook them.

[GregS]

for the light to flicker and the fans to cycle on and off there is a test connector that is still hooked up that is normally unhooked. Look under the drives side dash for a green conncetor and a black one (I believe they are single wire connectors) and if you find them together unhook them.

 

Just checked, they aren't hooked up

[tunered]

my haines manual says the only thing that makes the cel flash is what the above post says,now it goes on to say if they are unhooked and have the flash hook them back up,one way or the other should make it right.

[GregS]

my haines manual says the only thing that makes the cel flash is what the above post says,now it goes on to say if they are unhooked and have the flash hook them back up,one way or the other should make it right.

 

My original post might not be explained right. The cel should come on with all the idiot lights when you turn the key to the on position before you go to start position. (without the code connectors plugged in). Mine isn't coming on, or when it does it is just a very dim flicker while the car is in it's "failed mode". After the 45 minutes of waiting when the car will start again, the cel is on and steady like normal in the on position and then it goes away after I start the engine.

[kevinC]

The black connectors when hooked together will flash your codes. If no codes are logged there will be a steady flash. If the light goes dim it sounds like power is being limited to the ecm. The ecm has its own power supply inside. (think 12 to 5). the ecm pulls apart fairly easy. you might look for cracked or melted solder joints on the ecm. The ecm is under the dash by the connectors. gold box 4x6 . also ground to the ecm. Also do you have a good 14volts while the car is running. check all body grounds also. Good luck ((1990 legacy 228,000))

[Legacy777]

It's possible the bulb is not in tightly, something is screwy with the combination meter, or the ECU is going.

[Log1call]

That will be the main relay, it is controlled by the ECU and also turns on the main power to the ECU. It's high up in the kick panel, right above the fuel pump relay. They are both on a bracket which you can unbolt and pull down to get at them. The fuel pump is a round relay and above it is a square brown relay which is the, "main relay".