Ongoing Issues/Mystery with my Lexus es300 1994 please help

1995 LEXUS ES
143 MILES
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LARRYYARB
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Lexus Es300, 94, 143k miles. I was having issues with my od light flashing and cel with my car..high rpms and hesitation..Replaced one speed sensor to the advice of a mechanic..no improvement..

Lexus Dealer said get another ecu..I recently changed out the ecu for a used one. The cel and od light came back on after a few hours. Tried resetting the ecu did not help..Getting codes: P0500 and P0720

What can I do?

thanks Larry
Mar 5, 2012 at 1:52 PM
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LARRYYARB
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Also, what parts do I need to replace?
Mar 5, 2012 at 1:54 PM
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WRENCHTECH
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The TCM has some transmission specific codes that need to be retrieved using a professional scan tool with trans software.
Mar 5, 2012 at 1:55 PM
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LARRYYARB
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Here are the codes they found. .Getting codes: P0500 and P0720 ..these were the same ones with the old Ecu
Mar 5, 2012 at 2:13 PM
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WRENCHTECH
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Those are generic PCM codes. They are saying there is a problem with the output speed sensor circuit but the issue may not be the sensor itself and it needs to be troubleshooted further.
Mar 5, 2012 at 2:19 PM
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LARRYYARB
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The dealership told me to replace the dash cluster as well. They said to replace dash cluster and ecu at the same time to fix it...Does this make sense to you?
Mar 5, 2012 at 5:03 PM
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WRENCHTECH
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I couldn't tell you. They are the one's that tracked down the wiring diagram.
Mar 5, 2012 at 5:51 PM
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LARRYYARB
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I just dont understand how the communication btwn ecu and cluster could affect the shifting..
Mar 5, 2012 at 6:03 PM
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LARRYYARB
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I would be more likely to make a donation if I could get some probable causes to test out. Instead of I couldnt tell you
Mar 15, 2012 at 1:22 PM
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LARRYYARB
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Ok, I replaced the dash cluster and pcm/ecu. Everything has been working fine but now the speedometer is not working. all the other gauges are working.

There are no cels either.

Did I get a bad ecu/pcm? Or bad dash cluster?
Mar 28, 2012 at 12:27 PM
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WRENCHTECH
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Any of that is possible or it could be a wiring or speed sensor problem too. It needs to be diagnosed properly to find out.
Mar 28, 2012 at 12:30 PM
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LARRYYARB
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I replaced the dash and ecu..The problem has come back. still getting check engine light. Maybe I need a New ecu? I wonder if I got a bad ecu?

what do you thinK?
Apr 4, 2012 at 1:24 AM