I have a fairly cheap OBDII scanner and was monitoring it on a test drive today. My EGR percentage reading was all over the place from 61% to 0%. I understand that the max EGR percentage should be 21% on a 2011 Prius. Are the readings just the result of a poor scanner or (more likely) a poor operator (me)? Can you tell anything about the status of the EGR system from these readings? Thanks, James
Sorry it has 165,000 miles. No real problems though I have seen a 2-3 mpg decrease in fuel efficiency the last several months. The cause of the loss of mpg is what I am trying to figure out. Thanks, James
You’re getting restricted in the egr circuit. Time for the complete egr circuit cleanse . Loss of mpg can be other things (tire pressure, weather, etc), but the egr circuit restriction I found to drop my mpg about 3-4 mpg. I could see the change over time as I keep an eye on it. Good luck and keep us posted .
Start by checking the EGR pipe, it's easiest to access and will give you some idea of the rest. See @NutzAboutBolts video on this, and the whole circuit cleaning too, at top of 3rd gen maintenance forum. There's some good threads too: just google priuschat and EGR.
The EGR pipe was pretty dirty though far from fully plugged up. I will tackle the full EGR system cleaning as soon as I get time. I need to do my mom's car also. I think I will buy a new EGR cooler and install it on one vehicle and clean the old one then install it on the second prius so there is little downtime. Thanks, James
You can check eBay for egr coolers. You may also want to do a search for them and find different junk yards that may have them.
The pipe isn't likely to be fully plugged, but if it has significant carbon then the cooler likely is.
Good point. The passageways in the cooler are very constricted. An eighth inch build-up on the pipe just constricts it a bit. The same amount of build in the cooler would be pretty bad.
My scanner is the Ancel 410 I believe. I unfortunately don't know much about scanners. I am assuming that EGR_PER is EGR percent but you know how that goes. James
Dang, i just bought a different scanner that doesn't have the EGR monitoring! I wish i had seen this post. But plugging the 410 into the tracking app, it looks like Amazon does Lightening deals on this scanner quite a bit bringing the price down to ~$32. They don't last long and usually in the middle of the night, but at least it's a heads up. edit: I just checked the scanner i purchased (the autel al319) and it also has live stream with EGR_PER. Took a quick drive around the block and it stayed at 0.0%. I'll do another test on my drive home and see if that changes.
Here are my readouts from my drive home. The % did fluctuate depending on accelerating/decelerating but never got above 68%. When the ICE shut off, the egr % instantly dropped to zero. My clean EGR has a little over 4k miles on it, so doubtful it is clogged. 65 mph 5 min after starting. 65 mph 20 min at speed 80 mph 30 min at speed
