cassidy123

Hello all! i'm trying to figure out my egr system for my Lexus. I've been scouring the internet/forums, and I've only found info on different types of lexus cars (like the ls400). My car is throwing a code 71 - the CEL comes on and off periodically. I need to get my car smogged in about a month and I live in California so I need to check engine light to be off. It hasn't turned off like it usually does. The EGR valve that's on my car seems to be different (electric?) from others, and as far as I can tell it doesn't have a vacuum modulator. Most threads I've seen say to test the EGR valve using a vacuum but the directions are for EGR valves that look different from mine. I don't know how to fix this and I'd rather try and do this myself before going to a mechanic. Please be patient with me, I'm trying to learn more about my car and the engine. I don't know much, but I'm trying. I'm going to attach some photos of what my EGR valve looks like. In the photos it's disconnected. Please let me know any additional info/photos you might need. Thank you in advance for your help!!! I'm not sure if it's the temp sensor, or what and I have no idea how to test it.

KahnBB6

iTrader: (5)

Hello Cassidy. I am not familiar with how the 1992-1997 SC400's EGR system differs from the SC300's system but your issue could be related to a component failure, carbon buildup clog in the EGR passages or both.

If that is the SC400's EGR valve it looks to me like you have a fairly easy way to remove it from the intake manifold and then also remove the actuator section (the black part with the plug end on it) from the main valve. Generally to clean these parts, (while also being careful not to spray anything onto any sensitive electronic sections!), you will need to use a small scraping tool and CRC Carb & Choke cleaner. Do wear an N95 rated mask (fairly cheap) and protective goggles and 5mm nitrile gloves (Harbor Freight) while spraying any of that.

The EGR VSV should also be given a +12V test with cheap alligator clip leads on the correct terminals for positive and negative along with a simple vacuum pump test to see if it holds and releases pressure correctly. These procedures for testing the VSV are listed in the SC300/400 TSRM.

I am having trouble finding the link buried somewhere in CL where the full SC400 TSRM in PDF format is hosted for downloading. I have this manual but no way to link it to you (too big to post) unless something like Google Drive were to be used.

There is also giving yourself a couple of days subscription to the Toyota TIS (Total Information System) to look at any and every technical manual on the SC400 and download them there but if the PDF link can be located or some sharing service arranged many of us here do have the factory service manual in PDF form (as well as all the wiring diagrams).

The other thing is that the EGR passages themselves inside the intake manifold, any EGR pipes & hoses and the EGR exhaust port on one of the cylinder heads may need some cleaning to remove carbon buildup.

The EGR valves themselves rarely go bad but you never know with the cars being so old now. Still, they're extremely well built parts. The EGR VSVs can eventually fail but even long after the cars were produced a lot of those VSVs are still working fine. I don't know if the SC400 has an EGR vacuum modulator like the SC300 but as long lasting as that OEM Toyota part is they too, eventually, can suffer a stressed and failed internal diaphragm with extreme age.

Generally though all of these parts tend to have very long service life so long as the EGR passages are clean.

It is not directly relatable due to the designs being very different but when I had to sort out my 1993 SC300's EGR Code 71 issue methodically and step by step I found that the main cause of my issue was actually a clogged EGR passage in my intake manifold. That had to be either cleaned out or I had to replace the whole intake manifold section with a new one (I chose the latter option at the time but cleaning it FULLY would have solved the issue just the same). It also turned out that my EGR VSV also needed to be replaced as well as the EGR valve but my car had a lot of miles on it (240k or so by that time).

Even after replacing those parts and verifying proper function of the rest of the EGR system it finally did come down to dealing with cleaning the intake manifold's clogged EGR passage to finally make the CEL Code 71 go away for good. Just FYI, every time you perform a battery reset you may make the Code 71 go away for a while but you have no good confirmation unless that code does not come back after a bit more than 100 miles of driving around (use your Trip Odometer to measure mileage after every battery reset).