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I have 2000 ls 400, I've been having my check engine light on for a while. The car has also been experiencing limp mode, slow acceleration, bad fuel economy, speedometer coming on and off, the VSC staying on. I decided to go get a diagnostic to see what was wrong with it. Before i had it tested i wanted to use my own ob2 scanner to see what the dtc codes were, P1354 p1351(I tried switching out the solenoid, didn't do anything, and my timing belt was good). p0763. After i did my diagnostics, i got totally new codes, which were (P1125,P1755,P1765,P1656,P0763), i need help in what i should do with my car. i think i might have a ecu problem but i can't tell.
That list of codes is the throttle, multiple parts of the transmission and the oil control valve and have virtually no relation to each other and are SUPER random\rare to happen on this car.
When you add limp mode, speedometer, etc, you're just going down the ECU failure symptom checklist with everything you list.
I never had any symptoms of low battery while my 98 was dying a few years ago. Nothing like OP has. It was fine until it died enough and the amps dropped low enough that the starter motor solenoid tripped and it all started clicking, failing to turn the engine. That's when it threw a VSC code for me. Lights were kinda dim on the dashboard. But nothing else. Never once did it ever throw a code or check engine light or any of the other weird things. And my battery was kaput, one of the cells failed so it had like 10.something volts.
You guys are right though. Battery\power system is the far far far easier & cheaper solution, so best to start there & make sure that's good.
Agree with Battery/charger check. My 1998 did strange things throwing Check VSC etc when I had a weak battery for a while.
Problem Gone with new battery. Actually 70Ah AGM battery with enough cold crank amps.
These cost more but are longlived ,more rugged and better in most ways.
it's not those things, both of those check out to be fine the real thing is ecu, i just had guy put in a used ecu and he flash it but it wont turn the car over.
You have a 2000 LS400. That means the ECU has an immobilizer. Did you address that?
For cars with immobilizers (it varies depending on the region you're in whether it's fitted or not), you are far better off repairing the original ECU rather than replacing it because you do not have to deal with this system.
It is not as simple as swapping the ECU over between cars, immobilizer pinouts can be different, even within the same model year of car IIRC. You must have ECU's with matching numbers. Even finding an appropriate ECU can be challenging.
Generally the wisdom is to repair the later ECU's, unless there is physical damage to the board from the failed capacitors in which case you don't really have a choice.
Your current no-start on the new ECU, I'm guessing, is because of incorrect ECU serial, or, immobilizer. But I'm going to hedge my bets here, I would check the electrical system again. While not unheard of, 98+ ECU failures are much less common than the earlier cars. Maybe there is a bad ground. Or mice got into a wiring loom. Or maybe your testing process for the electricals was flawed. Testing is free, repair costs money. I'd make sure before repairing the old ECU.
If the electrical system is healthy, as far as I'm aware the ECU is the next most likely item. You've got throttle errors, oil errors, transmission errors. Bad speedo. Limp mode. And all of it is intermittent. Sounds like classic ECU to me.
It is not as simple as swapping the ECU over between cars, immobilizer pinouts can be different, even within the same model year of car IIRC. You must have ECU's with matching numbers. Even finding an appropriate ECU can be challenging.
Generally the wisdom is to repair the later ECU's, unless there is physical damage to the board from the failed capacitors in which case you don't really have a choice.
Your current no-start on the new ECU, I'm guessing, is because of incorrect ECU serial, or, immobilizer. But I'm going to hedge my bets here, I would check the electrical system again. While not unheard of, 98+ ECU failures are much less common than the earlier cars. Maybe there is a bad ground. Or mice got into a wiring loom. Or maybe your testing process for the electricals was flawed. Testing is free, repair costs money. I'd make sure before repairing the old ECU.
If the electrical system is healthy, as far as I'm aware the ECU is the next most likely item. You've got throttle errors, oil errors, transmission errors. Bad speedo. Limp mode. And all of it is intermittent. Sounds like classic ECU to me.
,
my electrical side is good, I do think why it won’t turn over is because I don’t have the immobilizer to match the new used ecu I got. But do you know a good place to send In my ecu for it to be fixed
I don't think it's an ECU issue.
If I were you, at first, using an oscilloscope, I'd check cam timings both advanced and non advanced. What I mean to say is that I check the relationship between the crank shaft rotation and the cam shaft rotations viewing signals from those rotation sensors. I wouldn't do any others without doing this.
I don't think it's an ECU issue.
If I were you, at first, using an oscilloscope, I'd check cam timings both advanced and non advanced. What I mean to say is that I check the relationship between the crank shaft rotation and the cam shaft rotations viewing signals from those rotation sensors. I wouldn't do any others without doing this.
Connect proves to each sensors and observe signals and check switching phases as well as the amplitude.
Sorry that this is for those who can handle an oscilloscope and not for everyone. Electronics controlled cars often need an oscilloscope to troubleshoot. Without it, troubleshooter will be throwing parts next to next and spend extra time and money for what are not needed and still can't find the root cause of the problem.
01-28-23, 03:33 AM
I need helppp with ls 400
