Speedometer and dash lights not working properly and Code PO500

Tiny
MWILSING
  • MEMBER
  • 2004 LEXUS GX 470
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 187,000 MILES
My vehicle became weird today. The speedometer works at random. Mostly not at all but sometimes kicks in for a few minutes then drops back out. The VSC TRACK and VSC Off lights stay illuminated. Brake light is on and also the ABS light is on. I pulled the one code which is PO500 for a speed sensor.A Should the other lights go off if I clear the code, because they do not. I am hoping it is just a speed sensor but almost sounds like possibly something else even with the PO500 code. Something else I noticed is fuel gauge now fluctuates. Saw it drop down to empty and light came on and then it went back up to half where it originally was. Help!
Saturday, January 25th, 2020 AT 2:03 PM

24 Replies

Tiny
STEVE W.
  • MECHANIC
  • 14,478 POSTS
Clearing the codes will not turn off any lights if there is a failure turning them on. A speed sensor failure would cause all of those lights as the ABS and Stability Control both use the sensor for operation. In reality they are the same systems, stability control works using the ABS system to modulate the wheel speeds to maintain traction and stability. That code can be caused by either a bad speed sensor or the wiring harness for it. The speedometer acting strange also says it is a real failure. To verify which sensor has the issue use a scan tool with live data to watch the output speed sensor while driving. If you see it drop out then you have the culprit.
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Sunday, January 26th, 2020 AT 8:22 AM
Tiny
MWILSING
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  • 36 POSTS
I pulled the plugs off the sensors and probed the two leads coming from each. Left front I could not get a reading at all like it was dead. (No good )
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Sunday, January 26th, 2020 AT 12:05 PM
Tiny
STEVE W.
  • MECHANIC
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You won't get a reading from them unless they are connected and the vehicle is in motion.
The sensor that is causing the problem should be the one mounted in the transmission, not the ABS wheel speed sensors. That is why you need the scan tool to allow you to read live data from the 4 ABS sensors and compare those to the output speed sensor in the transmission.
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Sunday, January 26th, 2020 AT 9:51 PM
Tiny
MWILSING
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  • 36 POSTS
Any idea where about this sensor is located? Its a 4.7 ltr v8 4x4 I know there are two. Would like to inspect before paying the dealer costs.
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Monday, January 27th, 2020 AT 11:44 AM
Tiny
STEVE W.
  • MECHANIC
  • 14,478 POSTS
Both of the sensors are on the side of the transmission toward the top of the case about halfway back. The SP2 is the one monitored but they are both the same part number.
Bolt is torqued to 48 inch pounds. They are a simple coil sensor so just measuring them both with an ohmmeter should tell yo if one has failed. I would look close at the connector as it is easy for water to get in and corrode the pins.
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Monday, January 27th, 2020 AT 1:51 PM
Tiny
MWILSING
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  • 36 POSTS
Drivers side correct?
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Monday, January 27th, 2020 AT 11:04 PM
Tiny
MWILSING
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  • 36 POSTS
Having a hard time finding the sp2 sensor. Added a photo of similar tranny. Is it more top towards shifter lever?
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Monday, January 27th, 2020 AT 11:33 PM
Tiny
STEVE W.
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You may have the later version that has one on each side. There will be one to the front drivers side that measures the input shaft speed and one toward the rear passengers side that reads the output shaft speed if it is the later transmission. The second one is the problem on your vehicle.
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Tuesday, January 28th, 2020 AT 2:48 AM
Tiny
MWILSING
  • MEMBER
  • 36 POSTS
That's what I saw when I was under the vehicle. So in this case it is still same part number for both? Will dig into it again after work. Thank you.
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Tuesday, January 28th, 2020 AT 8:57 AM
Tiny
STEVE W.
  • MECHANIC
  • 14,478 POSTS
That's what they show, Part # 8941332010 supersedes to #8941332011
The really weird part is the price ranges on that part. Toyota gets $158.00 for it but I see the same part number listed for under $20.00 at rockauto !
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Tuesday, January 28th, 2020 AT 9:09 AM
Tiny
MWILSING
  • MEMBER
  • 36 POSTS
Same here. I ordered one from my hometown Napa store. Will be here in the morning. $24.97 Thank you again. Will update as to what I find.
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Tuesday, January 28th, 2020 AT 9:25 AM
Tiny
MWILSING
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I also removed the battery cables to try to reset everything. Little did I know I have to reset everything, lol. Windows/key fob. I love Lexus. Lol
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Tuesday, January 28th, 2020 AT 9:26 AM
Tiny
MWILSING
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35000-60A60 is number on sticker on transmission from what I can read. Also I would assume this is the culprit on passenger side?
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Tuesday, January 28th, 2020 AT 10:09 AM
Tiny
STEVE W.
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Yeah, that is one of the reasons I don't tell people to try to clear codes that way. You are lucky, some of the newer Toyota and Lexus cars will lock you out if the battery is disconnected, the immobilizer trips and you need a dealer code and tool to reset it.

That is the part. The passenger side is the one that is your issue. I would check the wiring from the sensor up as the way it is acting is a bad harness. There are a few numbers depending on which of the brands you search under.
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Tuesday, January 28th, 2020 AT 10:22 AM
Tiny
MWILSING
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  • 36 POSTS
Should I get any readings at the connector at the sensor? Key on/ key off?
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Tuesday, January 28th, 2020 AT 10:25 AM
Tiny
STEVE W.
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The green wire is the sensor ground, The red wire is sensor bias voltage. So either 12 or 5 volts on the red wire when referenced to ground with the key on.
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Tuesday, January 28th, 2020 AT 10:42 AM
Tiny
MWILSING
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Red was 1 volt. Green I got nothing grounded to frame.
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Tuesday, January 28th, 2020 AT 11:10 AM
Tiny
MWILSING
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I used a better tester and I checked both leads coming into both sensors. I have 1.2 volts at both and no ground to either. My friend is a Toyota tech so I guess its time to drop it off. May be beyond what I can do unless you have more ideas. Too hard to follow leads from under the truck with very limited space.
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Tuesday, January 28th, 2020 AT 11:55 AM
Tiny
MWILSING
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He is not a Lexus guy so he said it may take a while to figure it out.
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Tuesday, January 28th, 2020 AT 11:56 AM
Tiny
STEVE W.
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Sounds like a wiring issue, hopefully he has access to better information than what they give the aftermarket. Please let us know what he finds. It may help someone else, and thank you for using 2CarPros.
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Tuesday, January 28th, 2020 AT 12:49 PM

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