Got a code 71 from this 1993 Ls400 i recently purchased. Read through this forum-> https://www.clublexus.com/forums/gs-1st-gen-1993-1997/283263-code-71-egr-problems-read-this.html. But I am quite confused as I cannot find my egr vaccum modulator. I’ll attach an image of my engine where the vaccum modulator supposed to be, can anyone explain why I don’t have one there? Maybe I’m missing something but I just can’t find anything on the internet about this, Just trying to clear this code lol

 

Well, the problem is the thread you read was for the GS, which has a different engine and EGR system

Your 93 LS uses an updated VSV actuated EGR. The actuator is the round object with a plug you see beside the intake. The earlier 1990-1992 LS used the more analog vacuum operated system, similar to the thread you saw

An EGR diagram should be on the back side of your hood, near the grille. Look through this forum for a 93-94 egr thread

 

There don't seem to be a ton of threads of folks diagnosing 93-94 LS 400s with this problem... There are more for 90-92

I would start here:
https://charm.li/Lexus/1993/LS%20400...n/EGR%20Valve/

Keep in mind that removing the valve will affect the gasket and the coolant... You may want to go through a few other multimeter tests before you do that.

Have a look through and expand all the sections -> look for EGR with ctrl+F:
https://charm.li/Lexus/1993/LS%20400...d%20Diagnosis/

Also check and make sure you have no vacuum leaks. I see the clamp for the idle up valve hose going to the front of your intake is not holding the hose at the intake

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Code 71

EGR System Malfunction

(1) Open or short in EGR step motor circuit for 1 sec. or more
(2) EGR gas temperature is 75 degrees (C) / 167 degrees (F) or below for 1~4 minutes under conditions (a) and (b). (2-trip detection logic)

(a) Engine coolant temp: 65 degrees (C) / 149 degrees (F) or more
(b) EGR operation possible (EX. A/T in 3rd speed, A/C ON, 60 mph, Flat road).

 

Ok so I got back home and turned the car on and it had a rough idle. I check for codes and it gave me codes 71 and 41, i suspected the ECU could be the problem so I took it out and opened it up and at least half of the caps had leaked all over the board. I was just wondering could a leaky cap ECU cause a code 71 and 41 to happen and if I replace the ECU will it fix the CEL?

 

Sorry for your trouble but at first you need to repair the ECU and you will know those 2 codes are related or not. Judging from the age of your car, I worry that traces around capacitors are already damaged by the leaking QAS.

 

Bought a rebuilt ECU and it cleared all my codes and runs perfect now. If anyone else has these problems CHECK YOUR ECU!!

 

Thanks for the update. So the ECU fixed your problems. Anyway congratulations on your success.