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ls400 98 fault codes p0171 p0430

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Old 10-11-16, 12:23 AM
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rapikon
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Default ls400 98 fault codes p0171 p0430

Good day CL!

I need some help with my car, I have a 98 ls400 and i have been struggling with some codes. I had a P0171 code and changed my vacumm lines then it was solved. Now I have another code of P0430, i have an obd2 bluetooth dongle connected to my phone and i tried erasing my code, then after some miles of driving after I turn the car off it will have another code, the p0171. So I tried checking it a couple of times that it might be just a coincidence. But its been a week since I have both codes (p0171,p0430). And everytime I erase one other one will pop when I use the car the next trip i make. Is it a possibility of an ecu problem?

Just a heads up, I just changed my coolant temp sensor OEM, thermostat and rubber gasket (OEM), I also just did new sparkplugs.

thanks in advance!
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Old 10-11-16, 06:28 AM
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Originally Posted by rapikon View Post
Good day CL!

I need some help with my car, I have a 98 ls400 and i have been struggling with some codes. I had a P0171 code and changed my vacumm lines then it was solved. Now I have another code of P0430, i have an obd2 bluetooth dongle connected to my phone and i tried erasing my code, then after some miles of driving after I turn the car off it will have another code, the p0171. So I tried checking it a couple of times that it might be just a coincidence. But its been a week since I have both codes (p0171,p0430). And everytime I erase one other one will pop when I use the car the next trip i make. Is it a possibility of an ecu problem?

Just a heads up, I just changed my coolant temp sensor OEM, thermostat and rubber gasket (OEM), I also just did new sparkplugs.

thanks in advance!
I had those codes on my 1996 LS400 shortly after I bought it. It turned out to be leaking exhaust around the flange of one of the upper catalytic converters(on my car it was the flange just past the catalytic converter). If you put your car up on jack stands and crawl underneath, you should be able to hear the leaks. You can buy a can of muffler stop leak to patch the leaks(if that's what it is).
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Old 10-11-16, 09:25 AM
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rapikon
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jaaa. thanks man. i have a patching compound that i can use for exhaust leaks. ill try it tonight hope itll fix it. does your car respond better in mpg after fixing it? im doing 20 to 21mpg combined now. i hope to have mine back to 29mog highway and 24mph city.
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Old 10-11-16, 10:00 AM
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Originally Posted by rapikon View Post
jaaa. thanks man. i have a patching compound that i can use for exhaust leaks. ill try it tonight hope itll fix it. does your car respond better in mpg after fixing it? im doing 20 to 21mpg combined now. i hope to have mine back to 29mog highway and 24mph city.
No change in mileage, just fixed the CEL light. BTW, mine was a 420 code which is the driver's side cat. Yours is a 430 so it should be on the passenger cat side.
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Old 10-13-16, 09:32 AM
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just to follow up the thread, i did fix the codes now thanks to you jaaa, i saw that one of the flanges has a small carbon buildup so i assumed thats where the leak comes from, i have a spare exhaust paste to cover it up, now i dont have any error codes for 2 days. ill check once in a while abd see if it resolved the problem permanently. thanks again sir!!
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Old 10-13-16, 09:59 AM
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Originally Posted by rapikon View Post
just to follow up the thread, i did fix the codes now thanks to you jaaa, i saw that one of the flanges has a small carbon buildup so i assumed thats where the leak comes from, i have a spare exhaust paste to cover it up, now i dont have any error codes for 2 days. ill check once in a while abd see if it resolved the problem permanently. thanks again sir!!
I had to redo mine about three times, as I got to feel progressively smaller leaks. Some were just pin hole size. If you check while it is running, you can hear and feel the breeze caused by these leaks. In any case, the fix is quite cheap. Many times the shops will blame a cat on this. They make a lot more money changing out a cat than patching a leak.
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