Cross posting, need help troubleshooting the LX (2 Viewers)

[2manycruisers]

I was absolutely certain my cold weather no throttle issue was a bad accelerator pedal position sensor (APPS) from everything I found online. Bought a new OEM throttle body with APPS, TPS, and throttle motor last winter and after riding it around in the back floor all year, I finally installed it only to discover it didn't fix my problem. Posted to the 100 forum and has been crickets so far. Hoping someone has some ideas I can try.

Need help with P0120 code troubleshooting 2000 LX

I have a 2000 LX470 with about 270k. I replaced the entire throttle body with a NEW OEM unit to fix what I thought was a faulty APPS. I have the same problem and today seems a little worse. Background: This vehicle is normally garaged and a second vehicle. Last winter I had two occasions where...

forum.ih8mud.com

 

[Mauser]

It could possibly be the ecu. What is the part number of your ecu?

 

[vegasfj40]

Are there any adjustments that need to be made or checked on the TPS?

 

[vegasfj40]

Also, it could be something in the ECU that's temperature sensitive. Could be a ground problem in the TPS circuit. Not sure how accessible the ECU is on the 100, but you could try removing it and keeping it inside where it's warm, then on a cold morning install it and see what happens.

 

[2manycruisers]

Edited:

I'm having trouble determining my ecm part number. On Lexus parts website where I can enter the VIN, I get no results. On lexuspartsnow searching for 2000 LX470, I get 4 part numbers that all supposedly fit, but have different production dates from 1998-2001. At parts.lexus.com, my VIN returned 89666-60261 which appears to fit 4/99-7/99, but my production date is 12/99 which appears to be 89666-60170. I'll check my production date when I'm home later, but I'm pretty sure it's during 2000.

I fear it's something like a ground problem that could be hard to find. It's parked at the house and I'm rarely there, but I've never had this occur parked in the garage until I tried it today. I tried warming the APPS then the TPS with a heat gun with no difference, then left a light bulb heating the TB up for a while again with no difference.

I compared resistances in the TPS between my old TB and the one Virgil loaned me and all are within 0.02 ohms of each other. I compared the APPS on my new TB, my old TB, and the loaner from Virgil and they were 2.3 on the old one, 2.4 on the new one and 2.56 on the loaner. They were all in the garage at less than 50 degrees air temp. Spec is 1.64 to 3.28 at 68 degrees.

Keep the ideas coming!

 

[Mauser]

I'm having trouble determining my ecm part number. On Lexus parts website where I can enter the VIN, I get no results. On lexuspartsnow searching for 2000 LX470, I get 4 part numbers that all supposedly fit, but have different production dates from 1998-2001. At parts.lexus.com, my VIN returned 896666026184 which appears to fit 4/99-7/99. I'll check my production date when I'm home later, but I'm pretty sure it's during 2000.

I fear it's something like a ground problem that could be hard to find. When I'm parked in the garage, I don't have the problem. When I park outside and it's cold I have the problem. I'd have to plan to pull the ECM and park outside on a really cold night to see if I can isolate it to the ecm. Maybe I can do that.

I did confirm the TPS measures are correct according to TechStream and my ScanGauge.

Keep the ideas coming!

I have an ecu that you could use to test.

 

[2manycruisers]

Which part number is yours? That would be great to try, thanks! Maybe I can get out there this weekend and pick it up. I need to sort it before it stays warm and goes away again. It started fine Sunday afternoon.

 

[Mauser]

Which part number is yours? That would be great to try, thanks! Maybe I can get out there this weekend and pick it up. I need to sort it before it stays warm and goes away again. It started fine Sunday afternoon.

I have both the 60261 and the 60170

 

[alia176]

Edited:

I'm having trouble determining my ecm part number. On Lexus parts website where I can enter the VIN, I get no results. On lexuspartsnow searching for 2000 LX470, I get 4 part numbers that all supposedly fit, but have different production dates from 1998-2001. At parts.lexus.com, my VIN returned 89666-60261 which appears to fit 4/99-7/99, but my production date is 12/99 which appears to be 89666-60170. I'll check my production date when I'm home later, but I'm pretty sure it's during 2000.

I fear it's something like a ground problem that could be hard to find. It's parked at the house and I'm rarely there, but I've never had this occur parked in the garage until I tried it today. I tried warming the APPS then the TPS with a heat gun with no difference, then left a light bulb heating the TB up for a while again with no difference.

I compared resistances in the TPS between my old TB and the one Virgil loaned me and all are within 0.02 ohms of each other. I compared the APPS on my new TB, my old TB, and the loaner from Virgil and they were 2.3 on the old one, 2.4 on the new one and 2.56 on the loaner. They were all in the garage at less than 50 degrees air temp. Spec is 1.64 to 3.28 at 68 degrees.

Keep the ideas coming!

This is a total WAG but try heating up the ECU itself to see if perhaps a cold solder joint is acting up when the ambient temp dips. If this cures it, some folks have "reflowed" the solder by sticking the ECU PCB inside a toaster oven. Had to do this on the old Benz, years ago.

I'm under the impression that all other sensors and devices are working properly and something inside the ECU is the culprit.

 

[imhighlander]

@Mauser sorry to hijack someone else's thread but I need to chat with you about an ECU flash/"virginization" so I can get master keys cut for my 1998 LC. I tried starting a "conversation" with you but I'm not sure I did it right. Please DM me if you can. Thanks.

 

[2manycruisers]

This is a total WAG but try heating up the ECU itself to see if perhaps a cold solder joint is acting up when the ambient temp dips. If this cures it, some folks have "reflowed" the solder by sticking the ECU PCB inside a toaster oven. Had to do this on the old Benz, years ago.

I'm under the impression that all other sensors and devices are working properly and something inside the ECU is the culprit.

I’ve thought about this because I thought that was the issue with the TPPS. My problem with this theory is the problem goes away when the engine is warm. I don’t know if the temp of the ecm would have changed that much. But Virgil has offered a sub to see if that helps, so I’ll try that.

 

[Mauser]

@Mauser sorry to hijack someone else's thread but I need to chat with you about an ECU flash/"virginization" so I can get master keys cut for my 1998 LC. I tried starting a "conversation" with you but I'm not sure I did it right. Please DM me if you can. Thanks.

You did it right. My messages have been getting backed up pretty bad. I just haven't had the gumption to do a whole lot the past couple of months.

 

[2manycruisers]

I tried Vegasfj40’s suggestion and put my ecm inside the house overnight. Plugged it in, connected the battery and still the same PO120 code.