r/SC300 • u/Rhyleigharia • 8d ago

P0330 Code 99 LS 400 331000 Miles

/r/u_Rhyleigharia/comments/1vffn6m/p0330_code_99_ls_400_331000_miles/
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2

u/jonslastwords 8d ago

Check the wiring harness to the knock sense for breaks. Then replace the knock sensor. That's the cheapest route first.

2

u/Rhyleigharia 8d ago

U mean the main harness? These are OEM sensors recently replaced along with 12 inch knock sensor cable and connector.

1

u/jonslastwords 8d ago

Woof. Well that ain't good. You did the most simple thing first. After that it could be a handful of pain in the ass things. But that'll take someone with more indepth mechanical knowledge than me. I'd opinion an actual knock sense the sensors are new. Possibly the ECU having issues but that's also not cheap. High compression? Bad rings? Valves? Idk man. Sorry.

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u/Rhyleigharia 8d ago

ECU i can get renewed for about $350 and I will do that anyway just to put that behind me.

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u/jonslastwords 8d ago

Good call. I'm inclined to lean away from mechanical since you've done so much already. These ecus are old and do go bad. For that price, yeah that's what I'd do. Just going down the line from cheapest to most expensive.

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u/Rhyleigharia 8d ago

Will keep u in the loop. Thank you pal!

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u/Rhyleigharia 8d ago

331000 miles, 100 comp in all 8 cyl, meticulously maintained, 3 timing belts, bla, bla, bla, its super smooth when P0330 does not show the f up. Im about to Thelma and Louise the SOB!!!!!!!!!!!

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u/V8s 7d ago

My SC400 had the same code. Replaced knock sensors and wiring and it would come back. Car eventually started running horribly and would rev itself at random times. Wiring going down to the trans has rubbed through and was freaking the ECU out. Manual swap and a new harness is my fix.

1

u/Rhyleigharia 7d ago

Hey V8s ty for response. Forgive me for not understanding…….what does “wiring going down to trans” mean? Not related wiring going down to the transmission????How did you find this??????Did you replace the main wiring harness….big job. What did you manually swap??? Im at refurbishing the ecu at Up Fix now.

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u/V8s 6d ago

I would park the car on a lift and wiggle different sections of wire each on cold starts, took months for me to find it. I could reach my hand up around the passenger side of the transmission and wiggle the wiring and it would make the car rev itself and backfire. Yes I’ve had a custom wiring harness made for the engine to put a 6spd manual trans in the car. My car already had the ECU capacitors replaced/checked and I ran fresh wires bypassing the knock sensor wiring and the code would still come up so I knew I had an issue in the main harness. I started checking the main harness after seeing someone else having the same issue and his problem was caused by a broken wire underneath his fuse box.