P0710- tracing a bad wire or connector?

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YFZsandrider

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I've got a p0710 code, which is transmission fluid temperature sensor. There is virtually zero information on this code on any of the forums. I ordered a new sensor from toyota, and after pulling tho old sensor, the two tested identical for resistance. So I'm sure it's not the actual sensor.

I had the transmission off to replace a bad rear main seal several months ago, and I'm afraid there's some kind of kink or break in a wire leading to the sensor. I can fix nearly anything on a car as long as it doesn't involve electrical work... How do I got about trouble shooting it?
 
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YFZsandrider said:
I've got a p0710 code, which is transmission fluid temperature sensor. There is virtually zero information on this code on any of the forums. I ordered a new sensor from toyota, and after pulling tho old sensor, the two tested identical for resistance. So I'm sure it's not the actual sensor.

I had the transmission off to replace a bad rear main seal several months ago, and I'm afraid there's some kind of kink or break in a wire leading to the sensor. I can fix nearly anything on a car as long as it doesn't involve electrical work... How do I got about trouble shooting it?
Click to expand...

Seeings you don't do electrical, go ahead and throw that new sensor in...if it works...great...if not...it's all electrical from there on.....the first link is troubleshooting the sensor..w/resistance values for cold/hot etc..... the second one is for troubleshooting the ECM & Harness....luck..!!!

http://tacoma.site40.net/4Runner_96...ypdf/02rmsour/2002/024runne/di/at/cip0710.pdf


http://tacoma.site40.net/4Runner_96.../02rmsour/2002/024runne/in/httecsy/htutdc.pdf
 
Thanks for the links, I'll take a look at them!

The sensor was 100 bucks, so I'll take it back before I just throw it in. I tested both sensors in water at both room temp and at a near boil. They had an identical reading, so I'm relatively sure the sensor is fine.
 
Update- so I put the new sensor in, since I had already purchased it. After resetting the computer and driving around for about 15 minutes, the light came right back on. It's got to be something other than the sensor. I'm at a loss for finding it and I have a hard time reading wiring diagrams.

If there's a more straight forward way of testing the wiring or testing the ECM, I'm all ears!
 
Have you tried a visual inspection of the wiring all the way to the ECU? Often you can find visible damage to the wire somewhere along the way.
 
A power probe is an awesome tool! For diagnosing electrical problems. You can send power, or ground. Vise versa. Which can tell you exactly what is going on. Of course a multi meter is useful also. But let's say you take a connector. And you put a power probe to each pin and send power or ground. What ever that function is suppose to work on. This can narrow down that pin thus that wire and what it needs to be fixed.
 
gamefreakgc said:
Have you tried a visual inspection of the wiring all the way to the ECU? Often you can find visible damage to the wire somewhere along the way.
Click to expand...

I think I've found my problem. Just visually looking at the wire coming from the trans temp sensor, there's a good bend in the wiring right next to the plug. A few months ago I pulled my transmission to replace a leaking rear main seal, and when I wasaw separating the transmission from the block, I missed disconnecting that one plug, and I ended up yanking on it. I didn't notice the code it must have thrown at the time, because I already had a CEL for plugged catalytic converters.

Anyhow, now my plan is to probe into the wires and test for resistance between them and the end of the plug. Does that sound like a good way to test it? And should I disconnect the harness from the ECM first? Also, if my break in the wire is right there, how do I go about fixing it, I don't want a hack job splice?

Thanks for the help guys
 
YFZsandrider said:
I think I've found my problem. Just visually looking at the wire coming from the trans temp sensor, there's a good bend in the wiring right next to the plug. A few months ago I pulled my transmission to replace a leaking rear main seal, and when I wasaw separating the transmission from the block, I missed disconnecting that one plug, and I ended up yanking on it. I didn't notice the code it must have thrown at the time, because I already had a CEL for plugged catalytic converters.

Anyhow, now my plan is to probe into the wires and test for resistance between them and the end of the plug. Does that sound like a good way to test it? And should I disconnect the harness from the ECM first? Also, if my break in the wire is right there, how do I go about fixing it, I don't want a hack job splice?

Thanks for the help guys
Click to expand...

See if you can use a multimeter to test the pins in the connector, at least for voltage/continuity. If the bad wire is a power wire, that's easy to fix, if it's a sensor wire, not so much without possibly creating another issue: introducing more resistance.

The bummer is there is no easy way to replace a sensor lead unless you can shorten the length a bit because splices and bad repairs in general can introduce more resistance, which may throw off sensor readings.

Can you replace the entire harness, or is it a sub-harness maybe?

If that's not an option, you might consider getting another sensor lead with the plug attached from a wrecked vehicle (as long as possible) then splice and solder the two together as cleanly as you can to the relative same length. Use silver solder and try not to increase the length of the wire too much, wire length itself equals resistance.

Good luck!
 
YFZsandrider said:
...my plan is to probe into the wires and test for resistance between them and the end of the plug. Does that sound like a good way to test it? And should I disconnect the harness from the ECM first? Also, if my break in the wire is right there, how do I go about fixing it, I don't want a hack job splice?
Click to expand...

If you are going to test the resistance on the wire and look for continuity (i.e. zero resistance), you need to isolate the wire meaning disconnect it at both ends. A better way to test is look for voltage drop if you can make sure you have a signal going through the wire. You keep it hooked up and test dc voltage from the beginning to the end of the wire (i.e. place your probes at both ends) - you should find zero or very close unless you have a break, corrosion, etc....

Regarding repair, I might try to solder it and seal with a shrink tube cover or, if moisture is not a huge problem in that location, you could use a shrink tube butt connection like this.....

https://www.amazon.com/Pack-Heat-Sh...3768&sr=8-7&keywords=shrink+electrical+splice

If you don't have sufficient length, if there is moisture or if you don't know where the problem is in the wire, you could just lay another wire in parallel to the harness....match the gauge wire currently in use.

Buckaroo
 
Last edited:
Thanks for all the replies so far! I'm having a hard time finding the ecm plug pin diagram for a 2000. If I'm calling it right name, I need to know where the wires coming from the transmission temp sensor are located on the ECM harness plug.
 
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