Xmanz

Started doing work on my 1999 sc300 a while ago because I was getting p0125 p0120 p0121 codes so I replaced the thermostat which was stuck open, I took out the throttle body and replaced the apps and tps but while I was still waiting for the parts to come in my battery (which i put in a few months ago) kept dying and after jumping it a few times determined it was the alternator. After fighting a rounded bolt for a week or so I finally got the alternator out and replaced before putting everything back since I had already takin out the throttle body I figured I should check the spark plugs and when I did there was oil in all the spark plug ports so I replaced the gasket in both valve covers. After everything was put back in the car and I jumped the battery again to start the car the engine would turn on and then immediately off when I let go of the key. I’m hoping the issue is with the wiring of the alternator because the wire connector broke and I lost the orientation of the wires but looked online and found it but I’m not 100% sure it’s correct. The codes I’m getting now are p1656 and p1300 did I do anything wrong or do I need to started looking at the ignition controls? Please help

Supra Dr

iTrader: (14)

I took out the throttle body and replaced the apps and tps
This where your problem began.

Xmanz

so ur saying the problem was replacing those sensors?

RudysSC

Those sensors typically have to be carefully calibrated (there are various threads on the topic), so replacing them is only part of the battle. Did you manage to find OEM parts? Aftermarket ones for those sensors tend to not work very well.

Xmanz

yes I did find the oem parts and I did get the car to engine to turn back on but a mechanic I’m conversing with about the issue advised that I should change the gaskets on the throttle and intake converter even though they looked fine because it sounds like there is a small vaccum leak

Xmanz

but honestly can those sensors not being calibrated stop the engine from starting or cause issues with starting?

RXRodger

iTrader: (2)

Those gaskets are pretty hardy, I have had mine apart multiple times on all of my cars and never had an issue with leaks and don't think I have ever replaced those gaskets. One common mistake is to miss the two nuts under the throttle body as you can just put the nuts on the bracket that holds the tb to the head. If the car were running you could spray a little brake cleaner around the sealing surfaces and if the engine reacts you have a leak. Not running will make that a little more difficult. But typically none of that will prevent the car from running, just runs rough. I suspect something else. I don't have an OBII car, so the drive by wire (sort of anyway) throttle control sensor you replaced may have caused this as others have said.

Xmanz

oh really? Thank you I think I’ll just make sure to put a gasket sealants around it just to be safe but I wasn’t thinking that was leaking either that’s just what the mechanic suggested because one of the vaccum hoses that connects to the valve cover ripped but that must just be it but im still waiting on the part to come in.

RXRodger

iTrader: (2)

There is no need for sealant if the gaskets are ok. It will just make it harder to clean up the next time they come apart, which they have to do to replace plugs, wires, etc.

Xmanz

I’m trying to upload a video of what the engine sounds like but it’s too big

Xmanz

alright thanks

Xmanz

but I did get the engine to turn on I have a video of what it sounds like but after it was running I noticed I think the starter electrical harness was disconnected