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I need the ECU Pinout diagram for a 1999 Lexus ES300 w/ a U140E transmission. I recently had the coolant bypass hose along with knock sensors changed for my 1999 Lexus ES300 and now have a P0710 code.
I've measured resistance on the PINs for the temperature sensor and the two times I've checked it's been 2.3K and 3.3K ohms. So I suspect it is working properly but there in the wire some where. Would like to measure on the ECU to confirm. Need to know where.
It looks right but I'm not experienced with electric diagrams at all.
I'm looking at the ECU on page 198 and 321 but I'm unable to tell which connectors I should be looking at on the ECU. I'm interested in tracing TH0/THO and E2 from the E3 transmission connector. I want to measure resistance on the ECU side or perhaps somewhere along the wire. It's been hard to measure resistance at the connector on the transmission since it gets so hot in there.
Also is this the correct routing for the E3 connector wire (see the drawing I attached).
Disconnect the battery first, then short out the pins you want to test. Look for a dead short at the ECU (with all the connectors removed). If you find a short you know the wires are good.
So I think the wiring on the 99 ES300 is different. When I disconnect cables 13 and 18 on ECU 10. The codes I get are for IAT, ECT, Throttle position sensor. And some other things.
i would expect it to be only for transmission fluid temperature, since the diagram shows it is an isolated circuit.
Where could I go about getting the diagrams I need? I was looking at the site below, but I have no idea if they are reliable. Plus it looks like they charge per system diagram. And not per car.
https://techinfo.toyota.com/ does allow you to download the unlimited amount of PDF files, though they are uploaded in chunks, so there are about 300 files that make up the complete book, but it shouldn't affect things too much.
If you measured the resistance of the Sensor on the ECU connectors in the interior and it came up good, I think your trouble area is elsewhere, one of the ways to know what it is would be to invest in a Techstream cable or a similar scan tool that allows you to see the actual readouts from your sensor, and monitor them as the car warms up, make sure to reset the CEL before hand in case it affects anything. There could be a loose contact or a cracked soldering somewhere on the sensor that may prevent it from functioning in a very specific scenario, just like in case of my VVT-i solenoid failure described in vivid details here.
So the wiring for the Transmission fluid temperature sensor is the same on the 99 ES300 and 2001. I'm noticing something weird and trying to make sense of it. When I disconnect pin 13 on ECU 10, I got an additional code of knock sensor 1 circuit malfunction. When it is plugged in no codes for knock sensor 1 but I do have a code for the transmission fluid sensor circuit short.
Why would I be getting a code for the knock sensor 1 on the circuit for the transmission fluid sensor?
I'm wondering if my mechanic ended up using the THO line as power for the knock sensor.
Another question, on THO-E2, where does power come from? The ECU on the THO line?
Last edited by 1st99ES300; Aug 23, 2023 at 09:54 PM.
So the wiring for the Transmission fluid temperature sensor is the same on the 99 ES300 and 2001.
Yes, it should be very similar.
Originally Posted by 1st99ES300
I'm noticing something weird and trying to make sense of it. When I disconnect pin 13 on ECU 10, I got an additional code of knock sensor 1 circuit malfunction. When it is plugged in no codes for knock sensor 1 but I do have a code for the transmission fluid sensor circuit short.
Which side of the connector are you looking at when you disconnect it? If I understand correctly, you de-pin the one specific wire from the rest of the connector to see if that's your issue. Every connector on the ECU has Pin Numbers written on the Back of it (on the Wiring side), check to make sure that you are pulling out the right wire, I've had that happen more times than I am willing to admit publicly..
Originally Posted by 1st99ES300
I'm wondering if my mechanic ended up using the THO line as power for the knock sensor.
Check if the wiring has been tempered with, if so, it will be a very worrying sign.
Originally Posted by 1st99ES300
Another question, on THO-E2, where does power come from? The ECU on the THO line?
It's a regular Resistive type sensor, it doesn't require any power coming to the unit specifically. Tthe sensor is connected to another, Fixed Resistor inside the ECU, which in turn, is connected to the 5V bus, forming a Voltage Divider, change in Resistance changes the properties of the Divider, causing the Voltage to change as well, here is an article with a detailed explanation.
Yes sir, I only use these because they are the best.
Originally Posted by 1st99ES300
So the wiring for the Transmission fluid temperature sensor is the same on the 99 ES300 and 2001. I'm noticing something weird and trying to make sense of it. When I disconnect pin 13 on ECU 10, I got an additional code of knock sensor 1 circuit malfunction. When it is plugged in no codes for knock sensor 1 but I do have a code for the transmission fluid sensor circuit short.
Why would I be getting a code for the knock sensor 1 on the circuit for the transmission fluid sensor?
I'm wondering if my mechanic ended up using the THO line as power for the knock sensor.
Another question, on THO-E2, where does power come from? The ECU on the THO line?
I don't see the knock sensor in the pic.
In the the context of THO wire I made some notes the best I can from what I can see, that's all I have on this.
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Appreciate the replies from everyone. The harness themself don't look tampered with, I suspect the mechanic might have done something while he was changing the knock sensor + wiring harness. I'm fairly certain I'm pulling the right pins, I've counted correctly for the female adapter per the wiring diagram from Toyota.
I think this weekend i will cut the THO wire from the transmission and run it directly into the ECU connector.
It's hard to inspect the work near the knock sensor since I would have to remote the plenum.
I think this weekend i will cut the THO wire from the transmission and run it directly into the ECU connector.
I would strongly suggest against it, as I doubt that this is your problem. Try getting a Live Readout of the sensor's signal, see if it is more or less correct and that it is stable at any range, all that was mentioned in one of the previous posts.
ECU Pinout needed
