I was driving home last weekend and suddenly, the CEL came on. Pulled code from ECU and got 71. Been searching through the forum here but was mainly able to find info regarding the LS400. I was also able to find some info for 97+ SC's but many have resorted to the EGR delete. I would love to delete this but I live in California and we all know what that means. Back to the LS400, I found this tutorial which essentially shows how to check and clean the EGR Vacuum Modulator in hopes to restore EGR valve functionality. However, looking at the engine bay photo of the LS400 and my '92 SC400, there are some things that are in the LS400 that are not in the SC400 (see photos below). My SC400 doesn't have this EGR vacuum modulator and VCV (not sure what that is). I do see that my car has the VSV which I think is the EGR valve solenoid (green arrow), and obviously the EGR valve itself (red arrow). Realizing that the tutorial that I found is pretty much useless, I went digging for more info and found another one. However, this one is for the GS. After reading the troubleshooting steps that the OP took, it seems that the LS and GS have similar EGR systems, they both have this EGR vacuum modulator that is absent from the SC. Steps 1 - 4 goes into details how to check the EGR vacuum modulator and touches on how to test the EGR temp sensor. Since my SC doesn't have these components, I am skipping these steps which brings me to step 5 - checking the VSV. Then the following steps will cover the EGR valve itself.

Before I dive into this, I would like to hear from other SC400 owners what they've done to clear code 71. In my past experience with this, the main culprit is the EGR valve solenoid. Either both lines coming into and from it are clogged, and/or the valve itself is faulty. I would like to try the simple stuff first before diving into the more complicated and most likely difficult steps to try and resolve this problem. Any suggestions would be greatly appreciated.


LS400 engine bay:



SC400 engine bay:

 

Dude,


On the engine hood of your car there should be a vacuum hose diagram decal. That should indicate what EGR components are supposed to be on the engine. For what it's worth, the EGR system does not take away any power from the engine. Removing it does not add any horsepower. It is strictly a smog-control device while you are at cruising speed.



- good luck

 

Thanks, I will check on that. I just want to clear the code so I can pass the upcoming smog test since this condition will definitely fail my car. I cleared the code yesterday by disconnecting the battery but the code came back today.