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Engine codes 52 and 71?

Tiny
LR_SC300
  • MEMBER
  • 1995 LEXUS SC 300
  • 3.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 163,000 MILES
I’ve recently purchased a 1995 sc300 and was retrieving the codes 52 and 71 from the ECU. I’m not very familiar with this car yet so I was hoping to get some advice on what to check or replace as a result of those codes.
Wednesday, May 3rd, 2023 AT 4:04 PM

6 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,192 POSTS
Hi,

Code 52 is related to the engine knock sensor and the 71 is tied to the EGR system.

So, I need to know how the vehicle is running. If it idles smoothly, I would suggest starting with the 52 code. If the vehicle has a rough idle, then start with the 71.

Let me know. If you want, I have attached the diagnostics for both below for you. Take a look through them and let me know if you are comfortable performing them.

Take care,

Joe

See pics below.
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Wednesday, May 3rd, 2023 AT 7:48 PM
Tiny
LR_SC300
  • MEMBER
  • 4 POSTS
Oh, okay, great thanks! Yeah, it doesn’t run rough at all, but the idle speed is messed up. From the moment you turn the key its idle speed will continue to rise and won’t come down until I put it in gear. Once in gear it stays somewhat normal.
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Thursday, May 4th, 2023 AT 5:06 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,192 POSTS
Hi,

Thanks for the info. Based on a high idle, I suspect the problem is related to the EGR. Are you comfortable performing the diagnostics I attached above?

Also, take a look at this link and let me know if anything helps:

https://www.2carpros.com/articles/engine-idles-too-high

Let me know.

Joe

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Thursday, May 4th, 2023 AT 6:51 PM
Tiny
LR_SC300
  • MEMBER
  • 4 POSTS
Hey thanks Joe, and I should be able to preform those diagnostics above. I will definitely let you know if anything changes.
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Friday, May 5th, 2023 AT 9:33 AM
Tiny
LR_SC300
  • MEMBER
  • 4 POSTS
Hello,

I replaces the EGR as it was bad, and the light went away. Although, the idle problem still exists. It will fast idle at about 3-4k rpm and remain that way even after the engine reaches operating temperature.
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Wednesday, May 17th, 2023 AT 4:55 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,192 POSTS
Hi,

Have you been able to check for engine vacuum leaks?

Let me know.

Joe
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Wednesday, May 17th, 2023 AT 9:08 PM

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