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1998 T100 SR5 2WD
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Discussion Starter #1
Does anyone know what type the transmission temperature sensor is? Is it just a switch?

Looking over the Electrical Wiring Diagram (EWD), it would appear to be a resistance sensor and not a switch as the switching happens in the ECU. I'm not sure if the ECU factors anything from the reading or not. I do know that if the transmission gits too hot, that the AT Temp light comes on. I'm sure the ECU would have to do something with that sensor...it's not something they would just throw in there fer a switch.

Since the Ultra-Gauge (not supported at this time) and the Scangauge II (not without the correct PID code which none of the Toyota ones so far work) readers currently don't support the transmission temp readings from the ODBII port fer my T-100, I'm tempted to tap into it from the sensor and hook up my Dwyer TCS module to it and see what I can read. I'm not sure if the added resistance of the wire will throw off the sensor reading or or by how much.

Looking over my Factory Service Manual (FSM), looks like the associated code would be P0710, Transmission Fluid Temperature Sensor Malfunction (ATF Temperature Sensor). So I guess I can't just pull the wire off... :(

I guess I can pull the sensor from my dead 1993 T-100 and use that fer my testing purpose... ;)

I know my other option is to put an inline connector from the ATF return line from the coolers and use an aftermarket sensor on there.
 

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1998 T100 SR5 2WD
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14,675 Posts
Discussion Starter #2
Haven't given up on this... :D

Seems the temperature sensor is the same across multiple vehicles.
http://www.toyodiy.com/parts/xref?v=U_1999_TOYOTA_TACOMA_VZN170L-CRPGKAB_8410&s=8942935042

Part 89429‑35042 (SENSOR, TEMPERATURE NO.2) was found on the following models:

Date range Model Frames/Options Found in diagram
08/1988-10/1995 TOYOTA 4RUNNER TRUCK RN10*,110,13*,VZN10*,110,13* 84-10: OVERDRIVE & ELECTRONIC CONTROLLED TRANSMISSION
11/1995-07/2002 TOYOTA 4RUNNER RZN18*,VZN18* 84-10: OVERDRIVE & ELECTRONIC CONTROLLED TRANSMISSION
02/1992-12/1994 TOYOTA 4RUNNER TRUCK RN101,110,VZN100,110 84-10: OVERDRIVE & ELECTRONIC CONTROLLED TRANSMISSION
01/1995-08/2004 TOYOTA TACOMA RZN161,171,VZN160,170 84-10: OVERDRIVE & ELECTRONIC CONTROLLED TRANSMISSION
01/1995-08/2004 TOYOTA TACOMA RZN140,150,19*,VZN150,195 84-10: OVERDRIVE & ELECTRONIC CONTROLLED TRANSMISSION
08/1992-06/1998 TOYOTA T100 RCK10,VCK1*,2* 84-10: OVERDRIVE & ELECTRONIC CONTROLLED TRANSMISSION
02/1999-09/2006 TOYOTA TUNDRA GSK30,UCK3*,4*,VCK30,40 84-10: OVERDRIVE & ELECTRONIC CONTROLLED TRANSMISSION

I know the 1999 Tacoma ECU will report the transmission temp via the ODBII port to a Scangauge II when you input the proper codes. I installed my Scangauge II reader into my neighbor's 1999 Tacoma 4WD auto and pulled up the transmission temps. So now I'm on a quest to see what it will take to pull the transmission temps from our old ECU...or hook up a temperature reader to the sensor to read the temps. ;)

I should be able to confirm with my neighbor's truck and the Scangauge II installed if hooking up wires at the sensor's connector or at the ECU will offset the temp and by how much. Keep yer fingers crossed... :D
 

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I've got a related question: We just bought a 93 T100 SR5 (our first Toyota and first pickup) and the AT Temp idiot light is on, but from starting up cold. Does anyone know whether the sensor tends to fail open or closed, and does it go through the ECU or is a discrete circuit to the AT OIL TEMP lamp?

Thanks for any/all advice.
 

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1998 T100 SR5 2WD
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Discussion Starter #4
I've got a related question: We just bought a 93 T100 SR5 (our first Toyota and first pickup) and the AT Temp idiot light is on, but from starting up cold. Does anyone know whether the sensor tends to fail open or closed, and does it go through the ECU or is a discrete circuit to the AT OIL TEMP lamp?

Thanks for any/all advice.
It defintely goes through the ECU (read my posts) and is NOT wired directly to the light.

I haven't seen a transmission temp sensor go bad before...but it could happen. Have you checked/traced the wiring from the sensor? You could check the resistance of the sensor with a multimeter and report back with the number. You'll have to pull the wire harness off the sensor to measure. ;)
 
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