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sc400 EGR DELETE --still throwing CEL code 71

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Old 08-30-10, 11:59 PM   #1
1UZFE_SC95
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Default sc400 EGR DELETE --still throwing CEL code 71

After installing S&S headers on the 1995 sc400 an EGR deletion was needed.

bought the kit from the guy at Lextreme and installed it with the resistor that came with it.

Now, I've read all the EGR forums (for sc400s) on this site and they all instruct to install the 10 ohm 1/2 watt resistor in the EGR probe, or egr temp switch.

well I did that, but guess what... she still reads code 71 (egr malfunction)

spent an hour trouble shooting it, clearing the code, starting it, changing the setup of the resistor...... tested the resistor.. appears to be good..

has anyone else had the same problem when doing the EGR delete??
The EGR valve solenoid also has a 6-pin power connector. I currently have it completely disconnected. does this need some kind of resistance also??

im kinda out of guesses at this point but Im gonna try a couple things soon like replacing the resistor....plugging in the egr valve


any advise would help.. thanks
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Old 08-31-10, 10:11 AM   #2
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If I remember correctly, I used a 10 ohm rheostat to get the cel off and it worked on my supra, make sure you connected all your vsv hoses right for the egr. I don't know if you deleted all your vsv's I think there are 2 or 3 of them, also do you have your o2 sensors plugged in and functioning properly?


Quote:
Originally Posted by 1UZFE_SC95 View Post
After installing S&S headers on the 1995 sc400 an EGR deletion was needed.

bought the kit from the guy at Lextreme and installed it with the resistor that came with it.

Now, I've read all the EGR forums (for sc400s) on this site and they all instruct to install the 10 ohm 1/2 watt resistor in the EGR probe, or egr temp switch.

well I did that, but guess what... she still reads code 71 (egr malfunction)

spent an hour trouble shooting it, clearing the code, starting it, changing the setup of the resistor...... tested the resistor.. appears to be good..

has anyone else had the same problem when doing the EGR delete??
The EGR valve solenoid also has a 6-pin power connector. I currently have it completely disconnected. does this need some kind of resistance also??

im kinda out of guesses at this point but Im gonna try a couple things soon like replacing the resistor....plugging in the egr valve


any advise would help.. thanks
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Old 10-11-10, 11:21 PM   #3
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Okay... well after plugging the EGR back in... guess what no code...

unplug it and boom.. CEL.

that probe resistor really doesnt do anything at all. with or without the resistor for the egr temp sensor doesnt matter. Its the 6-pin EGR valve that seems to need resistance to clear the code. Ive plugged the EGR back in now but i need to figure out which wires in the 6-pin connects need resistance..

help anyone??
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Old 07-02-14, 11:05 PM   #4
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Quote:
Originally Posted by 1UZFE_SC95 View Post
that probe resistor really doesnt do anything at all. with or without the resistor for the egr temp sensor doesnt matter. Its the 6-pin EGR valve that seems to need resistance to clear the code. Ive plugged the EGR back in now but i need to figure out which wires in the 6-pin connects need resistance..
Been doing some EGR research and ran across this thread while looking at what people did for deleting the system and getting around CEL codes. The above is particularly interesting, because I was going through the FSM's diagnostic tests on my '94 SC400's EGR pieces and was stumped by the step that calls for inspecting the EGR valve itself (EC-22).

The manual says to disconnect the 6-pin EGR valve connector and run resistance checks across various terminals. However, I have no such connector! It's the first thing I've run across in the manual that just plain doesn't match up. I don't remember what link I downloaded it from and whether that was year-specific... I'm guessing it applies to multiple years and that 6-pin connector is a significant element as far as why the EGR Delete works for some and not others, CEL-wise.

The OP has a '95. Did the EGR system change between '94 and '95 to include that 6-pin connector?
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Old 07-02-14, 11:45 PM   #5
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Here's an unanswered post showing the same no-connector setup as mine, this one on a '92 SC400:

http://www.clublexus.com/forums/perf...992-sc400.html

Also, I found an EGR thread saying that the EGR temperature sensor is located on (or connected to?) the EGR pipe. I'll take a look at that in the morning.
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Old 07-03-14, 01:47 PM   #6
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Just take the motor off the valve, plug it in and stash it under the intake. Problem solved!
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Old 07-03-14, 03:07 PM   #7
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Originally Posted by KC95SC400 View Post
Just take the motor off the valve, plug it in and stash it under the intake. Problem solved!
Was that for me? I can't figure out what you're responding to... And what motor, the VSV?
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Performance: Alternative BFI (BeeFI?), A/T Solenoid Bypass, M2/Manzo axleback exhaust (awaiting mid-pipe resonator delete), 2-Tone Driver's Seat ("performance" as measured by the butt test).
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Old 07-03-14, 04:08 PM   #8
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Quote:
Originally Posted by t2d2 View Post
Was that for me? I can't figure out what you're responding to... And what motor, the VSV?
To the other guy I guess but....

I'm pretty sure up to 94 uses a vsv operated EGR valve. In theory the only way the ECU knows the system is working is by reading the temp sensor.

95 and up uses an electronic valve. It uses the temp sensor and a position sensor in the valve motor. If you take the screws out of the motor and plug it in AND put a resistor on the temp sensor, the ECU shouldn't throw EGR codes.

I think in 96 and up, just to be complicated, the ECU reads the temp sensor to make sure that the valve is both opening and closing so it will throw a code regardless. Stuck closed or stuck open codes or maybe excessive / insufficient flow codes.
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Old 07-05-14, 11:33 PM   #9
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Gotcha. Thanks for the additional info. That's the one big thing I wish people would be more careful with here, specifying what model and year they're referring to. You pretty much have to assume people are talking about SC300s unless they specify otherwise, and I've been tripped up several times trying to find something on my car that was stated as applying to all years.

Anyway, I finished up my blanking plates today for the EGR valve and the EGR pipe into the manifold. The latter was a bear to get loose! I ended up rounding off one of the 12mm bolts pretty good, so I need to replace that before tightening it down or I'll never get it off again. I didn't bother trying to remove the bottom half of the EGR pipe, as that sounds pretty much impossible without a lift. I also left the EGR valve in place, since I haven't drained the coolant yet to disconnect those lines and bypass it. The modulator valve and VSV are removed, with the connector to the VSV just sitting there. I capped off the unused vacuum ports.

With all that done, I drove it around this evening, in town and on the highway, and didn't receive the dreaded Code 71. And no knock sensor (pinging) trips. Yippee. It sounds like you're right that the '94 only looks at the temp sensor. I finally figured out yesterday that the temp sensor is the little 2-wire probe up into the bottom of the EGR valve's mount. It sits on one of the valve's bolts. As long as that is left plugged in, the rest of the system appears to be content.

I'll be curious to see if there's any noticeable swing in mpg...

'95+ with the position sensor must be the mysterious 6-pin connector that shows up in the manual and various DIY guides.
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Performance: Alternative BFI (BeeFI?), A/T Solenoid Bypass, M2/Manzo axleback exhaust (awaiting mid-pipe resonator delete), 2-Tone Driver's Seat ("performance" as measured by the butt test).
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Old 08-10-14, 09:27 AM   #10
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Quote:
Originally Posted by KC95SC400 View Post
I'm pretty sure up to 94 uses a vsv operated EGR valve. In theory the only way the ECU knows the system is working is by reading the temp sensor.
I've had the EGR system deleted on my '94 for about 5 weeks now. Twice, I've gotten the Code 71 (EGR) engine light. The first time was 20 days after taking it out and came on in conjunction with a knock sensor (Code 55) trip which I've hopefully finally eliminated with ECU repairs that affected that terminal. The second time was two weeks later and I think came on just as I turned on the A/C, but I'm not positive.

I still have some troubleshooting to do with the A/C system. It works fine at speed, but when idling in Drive makes for some pretty rough RPM fluctuations. In Park or Neutral, the RPMs rise enough that it doesn't happen. I'm not sure if it's IAC or compressor (or something else), but that A/C rough patch often coincided with tripping the knock sensor in the past, so I assume it's all somehow connected.

Anyway, the pattern seems to be that the OBDI system only detects the missing EGR when something else comes to its attention. Has anyone else seem similar behavior? I'm not quite sure how to go about diagnosing (and more importantly, overriding) that, being such a sporadic incident.

Unfortunately, Code 71 won't clear on its own after a few minutes like Code 55, so it requires pulling the EFI fuse when it happens. At least it doesn't affect driveability like the knock sensor and its retarded timing, but I hate not checking right away to make sure there's not another code lurking.
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Performance: Alternative BFI (BeeFI?), A/T Solenoid Bypass, M2/Manzo axleback exhaust (awaiting mid-pipe resonator delete), 2-Tone Driver's Seat ("performance" as measured by the butt test).
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Old 09-08-14, 06:49 PM   #11
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I've gotten the Code 71 three or four times now and did some more research. Apparently, it gets tripped through a variety of conditions that are related to what the temperature sensor detects, but I'm not clear on why that only happens with the EGR system deleted unless doing so changes temperatures at the probe (by eliminating exhaust gases)?

http://www.clublexus.com/forums/perf...f-off-diy.html

Quote:
I had 71 code error . It is set when ECU do not see that EGR is working at some conditions (engine hot light throttle operations)
http://www.3si.org/forum/f1/resistor...h-pics-382054/

Quote:
Mitsubishi thread: the ECUs in these cars look for a single variable: the right temp. sensor voltage at the right time. Here are the conditions:

Coolant temperature above 180 degrees
RPM between 1800-2200
Constant load for 30 seconds.

The ONLY way to get code XX once you've deleted your EGR is to drive like this. If you never drive this low in the revs, or if you don't drive on the highway much, the ECU will never check the temp sensor voltage and you'll NEVER get the check engine light for EGR. This is why people argue about it and insist that their cars are quirky exceptions.
So, I went ahead and unplugged my temperature probe and added a 10 ohm 1/2 watt resistor to the harness side of the plug, pushing one leg into each pin housing. We'll see if that permanently disables the Code 71 CEL...
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Performance: Alternative BFI (BeeFI?), A/T Solenoid Bypass, M2/Manzo axleback exhaust (awaiting mid-pipe resonator delete), 2-Tone Driver's Seat ("performance" as measured by the butt test).
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Old 09-10-14, 12:02 PM   #12
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Quote:
Originally Posted by t2d2 View Post
I've gotten the Code 71 three or four times now and did some more research. Apparently, it gets tripped through a variety of conditions that are related to what the temperature sensor detects, but I'm not clear on why that only happens with the EGR system deleted unless doing so changes temperatures at the probe (by eliminating exhaust gases)?

http://www.clublexus.com/forums/perf...f-off-diy.html



http://www.3si.org/forum/f1/resistor...h-pics-382054/



So, I went ahead and unplugged my temperature probe and added a 10 ohm 1/2 watt resistor to the harness side of the plug, pushing one leg into each pin housing. We'll see if that permanently disables the Code 71 CEL...
Hi, I'm new here and new 1991 lexus LS400 owner , i'm having the same issue with code 71...Any news? did the code 71 got disabled for good? i know on my 1991 lexus LS400 the code 71 comes up after 21 miles of driving on the high way that is, i drive on the highway a lot to work, i've cleaned out the EGR valve reset CEL and still got the code 71... yesterday i cleaned out the vacuum modulator at work with carb clean and also replace the vacuum modulator filter since the old one was flat like a pancake, real dirty and crispy as hell and then i reset the CEL now i have to wait to see if it(code 71) comes back, if it does come back i will have to fab some plates at work and delete the EGR system completely... i'm heading to radio shack later in the day and buying a resistor so that i'm ready just in case the code 71 comes back around...
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Old 09-10-14, 01:25 PM   #13
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Quote:
Originally Posted by Cronik1UZ View Post
Hi, I'm new here and new 1991 lexus LS400 owner , i'm having the same issue with code 71...Any news? did the code 71 got disabled for good?
No CELs so far, but it's only been two days and I was only getting it once every couple weeks before adding the resistor, so it's way too early to say anything definitively.
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Old 09-14-14, 09:44 AM   #14
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Id like to delete as many things as possible to have a cleaner engine bay. As long as it produces positive results. Please keep us updated.
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Old 09-14-14, 09:59 AM   #15
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Still no CEL after close to a week and a mix of city and highway driving.
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Old 09-14-14, 09:59 AM
 
 
 
 
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