sub96

The engine is an EJ25, that's the 2.5 DOHC. I thought I was clear that the problem didn't seem to be with the EGR itself, which seems to function well. But with whatever else might activate the check engine code 0400. The system doesn't seem to know it's working at times, especially at higher elevations.

No responses? Looks like I'm on my own here.

96 Subaru, 125,000miles. I'm getting a EGR code 0400 once in awhlie. I've been clearing the code and forgetting about it. Seems to happen more often at elevations of 4,000 to 6,000 feet. I've checked the EGR valve for soot and cleaned what was there. After I warm the car up I can manually open the valve and engine goes into a stall at idle. When I rev the engine I can see the valve operate normally. What else could be causing the code?

I know this is an OLD topic, but I found it and had to relate my experience. If your going to change the rear differential fluid and you have already found the plug frozen this is my best advice. 1) Get the Metric set from Harbor Frieght with the 13mm socket. I got one for $8 with their coupon. The 1/2 inch driver will work, but I don't recommend it. 2) Many years of breaking hard bolts has taught me patience. Clean the area, treat with penetrating oil, tap gently and heat with propane. This can take awhile, overnight, multiple treatments. Be patient. It's most likely to move when hot and the joint has expanded. 3) Take the top/filler out first, just in case the bottom doesn't move. 4) Best option is an inpact hammer, but a jack and breaker bar can work. 5) The bottom plug has a magnet on it, clean it well. 6) When your ready to fill, heat your oil up in a bucket of HOT water. Get a piece of vinyl tubing, heat the end and force it onto the bottles nipple. The tube allows you to hold the bottle at different angles to almost drain it, 25 ounces will do it. Remember, your under the gas tank, don't go crazy with the propane. Just get it hot, spray with oil while hot and tap, tap, tap. My plugs hadn't been moved in 18 years and it took about three goes at it. Good luck.