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EDIT: The car was fixed! If your car is throwing codes P0100 and P0101, read this!!! Somehow, my 10 amp EFI NO. 2 fuse was completely obliterated, as Yamae mentioned is a critical part of our cars' operations. I switched over a 10A from my horn to replace the blown fuse, left the battery disconnected for a few minutes to reset the computer, and all is good once again! Attached are some photos of the fuse box in my 99. My finger is pointing at the 10 amp fuse you need to check. Took me 15 seconds, and saved me a ton of money! Now I can return my expensive MAF sensor as that was never bad to begin with.
1999 LS400, just recently replaced my leaky ps pump and shot alternator, dead starter, lower intake manifold gaskets, throttle body gasket, and coolant temp sensor. The car would not run right upon reassembly so I replaced spark plugs and upstream o2 sensors. This helped a lot, but the car still seemed unsteady and threw a CEL and VSC. So I got the codes read (P0100 and P0101-MAF flow circuit and MAF flow circuit range/performance).
Replaced the MAF sensor with a known working one, reset codes, and still threw the same codes.
Symptoms now: car starts up and idles okay cold, but after a bit the car starts vibrating a little. The car will drive *fine* if I take it easy on the gas, but if the motor is under load/I floor it the car sometimes sputters and loses power. There is a rev limiter at 3k, and no matter what it feels like the car has about 100 hp. I'm 99% sure this is the ls400's limp mode. I am not getting any misfire codes. Sometimes the car will idle extremely low (100 rpm) and sometimes it will idle just fine (500-600 rpm) and then dip idle. No weird smells or sounds. I'm leaning towards the MAF harness side having a break in the wire somewhere, but the wiring looks quite daunting as the harness becomes part of the coil pack/injector harness. I found a wiring diagram for the pigtail for a 95-97, but am not sure if it's the same for a 98-00. If anybody has any suggestions or advice that would be greatly appreciated. Thank you in advance.
1999 LS400, just recently replaced my leaky ps pump and shot alternator, dead starter, lower intake manifold gaskets, throttle body gasket, and coolant temp sensor. The car would not run right upon reassembly so I replaced spark plugs and upstream o2 sensors. This helped a lot, but the car still seemed unsteady and threw a CEL and VSC. So I got the codes read (P0100 and P0101-MAF flow circuit and MAF flow circuit range/performance).
Replaced the MAF sensor with a known working one, reset codes, and still threw the same codes.
Symptoms now: car starts up and idles okay cold, but after a bit the car starts vibrating a little. The car will drive *fine* if I take it easy on the gas, but if the motor is under load/I floor it the car sometimes sputters and loses power. There is a rev limiter at 3k, and no matter what it feels like the car has about 100 hp. I'm 99% sure this is the ls400's limp mode. I am not getting any misfire codes. Sometimes the car will idle extremely low (100 rpm) and sometimes it will idle just fine (500-600 rpm) and then dip idle. No weird smells or sounds. I'm leaning towards the MAF harness side having a break in the wire somewhere, but the wiring looks quite daunting as the harness becomes part of the coil pack/injector harness. I found a wiring diagram for the pigtail for a 95-97, but am not sure if it's the same for a 98-00. If anybody has any suggestions or advice that would be greatly appreciated. Thank you in advance.
So the 3k rpm limit is the 2nd limp home mode which is not as serious as the 1st one the 2k rpm limit. The 3k rpm one happens when the ECU is partially disabled due to the internal failure or the no power supply to the part of the ECU. The ECU needs 3 different power supply sources. It is a bit complicated to explain everything and to make a long story short, you need to check power supply lines related to ECU first. The highest possibility is the EFI-2 fuse line. The line is probably open or grounded while the jobs were done.
The pigtail for a 95-97 is not compatible, Simply check EFI-2 fuse and the related line.
1999 LS400, just recently replaced my leaky ps pump and shot alternator, dead starter, lower intake manifold gaskets, throttle body gasket, and coolant temp sensor. The car would not run right upon reassembly so I replaced spark plugs and upstream o2 sensors. This helped a lot, but the car still seemed unsteady and threw a CEL and VSC. So I got the codes read (P0100 and P0101-MAF flow circuit and MAF flow circuit range/performance).
Replaced the MAF sensor with a known working one, reset codes, and still threw the same codes.
Symptoms now: car starts up and idles okay cold, but after a bit the car starts vibrating a little. The car will drive *fine* if I take it easy on the gas, but if the motor is under load/I floor it the car sometimes sputters and loses power. There is a rev limiter at 3k, and no matter what it feels like the car has about 100 hp. I'm 99% sure this is the ls400's limp mode. I am not getting any misfire codes. Sometimes the car will idle extremely low (100 rpm) and sometimes it will idle just fine (500-600 rpm) and then dip idle. No weird smells or sounds. I'm leaning towards the MAF harness side having a break in the wire somewhere, but the wiring looks quite daunting as the harness becomes part of the coil pack/injector harness. I found a wiring diagram for the pigtail for a 95-97, but am not sure if it's the same for a 98-00. If anybody has any suggestions or advice that would be greatly appreciated. Thank you in advance.
Check your battery terminals and negative grounds.
So the 3k rpm limit is the 2nd limp home mode which is not as serious as the 1st one the 2k rpm limit. The 3k rpm one happens when the ECU is partially disabled due to the internal failure or the no power supply to the part of the ECU. The ECU needs 3 different power supply sources. It is a bit complicated to explain everything and to make a long story short, you need to check power supply lines related to ECU first. The highest possibility is the EFI-2 fuse line. The line is probably open or grounded while the jobs were done.
The pigtail for a 95-97 is not compatible, Simply check EFI-2 fuse and the related line.
To check the related line would I open up the fuse box and see what leads to the EFI fuse spot? Also, are there any tests I can do at the pigtail with a multimeter to read voltage/resistance? I read somewhere about 5V to the ECU...
To check the related line would I open up the fuse box and see what leads to the EFI fuse spot? Also, are there any tests I can do at the pigtail with a multimeter to read voltage/resistance? I read somewhere about 5V to the ECU...
First of all check EFI-No.2 fuse seeing the drawing of this my post although it's for a JDM. The fuse box is located behind the battery. Open the lid and check it using a multi meter. If it's not open, measure and inform me all voltages of MAF sensor's 5 lines when idling.
First of all check EFI-No.2 fuse seeing the drawing of this my post although it's for a JDM. The fuse box is located behind the battery. Open the lid and check it using a multi meter. If it's not open, measure and inform me all voltages of MAF sensor's 5 lines when idling.
I think a wire connection definitely got broken when he did the repairs to the car. These cars have wiring and connectors that get brittle with time.
I think a wire connection definitely got broken when he did the repairs to the car. These cars have wiring and connectors that get brittle with time.
Yes, I also think so too. What I worry about is that the MAF sensor's harness is damaged and some line(s) is(are) grounded or open. The important first step is to check the EFI-No,2 fuse. As far as I have experienced, all 3k rpm limit problems were caused by the semi grounded VG line or others. This often blows EFI-No.2 fuse. The rectangular below is tha MAF. There are 5 lines connected to it. Measuring 5 lines voltages, we can guess what is wrong.
Yes, I also think so too. What I worry about is that the MAF sensor's harness is damaged and some line(s) is(are) grounded or open. The important first step is to check the EFI-No,2 fuse. As far as I have experienced, all 3k rpm limit problems were caused by the semi grounded VG line or others. This often blows EFI-No.2 fuse. The rectangular below is tha MAF. There are 5 lines connected to it. Measuring 5 lines voltages, we can guess what is wrong.
EDIT:
The car has been fixed! My 10 amp EFI no. 2 fuse was blown, not sure how that happened but now no more limp mode or check engine light!
Glad ya got it fixed and runs good now. Yamae is the best.
But off topic; The wires (aftermarket) that you have running through the battery hold down should be moved a different way completely away from the battery and not rubbing up against anything metal which could cut through them with continuous rubbing.
My dad had this issue with his car not going past 3k rpm, drove it in limp mode for however long he had it. His 1996 LS400 was his pride and joy, he passed away last month, i dont want to sell the car because of the sentimental value, I thought it was a bad ecu so i purchased one off ebay and it still has the same issues, no error codes, checked the fuse and that looks good, im not sure what else to try, can someone help? thanks!
My dad had this issue with his car not going past 3k rpm, drove it in limp mode for however long he had it. His 1996 LS400 was his pride and joy, he passed away last month, i dont want to sell the car because of the sentimental value, I thought it was a bad ecu so i purchased one off ebay and it still has the same issues, no error codes, checked the fuse and that looks good, im not sure what else to try, can someone help? thanks!
Is it possible to check the inside of those 2 ECUs?
Do all those Nichicon capacitors look OK?
Does the car behave exactly the same before and after you changed the ECU or are there any differences?
Thanks for the update. Congratulations on your fix, datstockls. So it was just an open fuse EFI-No.2 as I predicted. I'm glad your car runs good now.
Got the same exact issue, changed out the No.2 EFI fuse still cant rev past 3k. car was driving fine this morning on the way to work. i was driving back home n car suddenly had a loss in power n started throwing vsc and the same “P0100” & “P0101” any suggestions? my wire harness is tucked up on the frame of the fender and double taped with electric tape also so i know my harness couldnt have gotten ran through
Got the same exact issue, changed out the No.2 EFI fuse still cant rev past 3k. car was driving fine this morning on the way to work. i was driving back home n car suddenly had a loss in power n started throwing vsc and the same “P0100” & “P0101” any suggestions? my wire harness is tucked up on the frame of the fender and double taped with electric tape also so i know my harness couldnt have gotten ran through
Have you checked voltages of MAF sensor's 5 lines when idling and 3000rpm?
10-17-20, 02:07 PM
3k RPM limp mode?
