J30 Transmission Temp Sensor

[yodawill2000]

Does anybody here know how to "Bypass" the transmission sensor with the correct Ohm resistor?
I read in the Q45 that its possible.
When its warm out (>80F) right about the time my transmission is warmed up the dang thing gets stuck in 3rd for about 30-40 seconds then goes back to lockup till I'm where I'm going.

anyone heard of that??
FYI I have the B&M super cooler inline.

[GerryO]

Fix for 2 problems in MK1 Automatic Transmission

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I am the original owner of a 1987 MR2 Auto with 136,000 miles. Over the years I have had 2 problem with the transmission and both times when I talked to transmission shops there only solution was rebuild it. Had I listened to them the first time the rebuild would have not corrected the problem. The transmission would not shift into overdrive until I had driven at least 5 to 10 miles. This problem was solved by changing a stuck thermostat. Seems as though the computer will not let the transmission shift into overdrive untill it is fully warmed up.

The second problem was a little more scary. The transmission would not shift into low gear when I came to a stop. But I could manually shift it in to low and it would work fine. Then it started sporaticlly shifting from low gear to 4th gear skipping 2nd and 3rd., the rest of the time it shifted fine. Seemed to act up more when it sat for a week or 2. Ordered a set of 3 Solenoids, #1, #2 and overdrive around 150.00 and had them installed. Just a matter of dropping the pan like you were doing and oil and filter change, removing the old and bolting in the new.Transmission is now shifting like a new one. Problem solved.

It just amazes how nobody has the ability to diagnose and repair things, there only solution is just rebuild it. Hope this post saves somebody a buck and takes a rebuild away from one of those shops that cant fix anything without rebuilding it.

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Last edited by Plyscamp : October 8th, 2011 at 23:52.

Copied from here:

http://www.mr2oc.com/showthread.php?t=433164

You may need to join in order to read the actual thread and it sounds like the temp signal/sensor might be flakey, as OD lock isn't supposed to happen until things are warm, or maybe a solenoid is very slow to open or close, or maybe a lighter foot on the gas pedal will help, which makes me think of replacing the TPS or a kick-down switch adjustment?

[yodawill2000]

I agree.
I'm pretty sure is temp related.
This morning it was in the 60's and I had no issue,
Fluid is pink on the paper towel test.
And it shifts perfectly until that weirdness pops up on a warm day.
And here in Texas July and August is one big OVEN !!


GerryO do they mean the Thermostat in the coolant circuit , Or is there one in the transmission ??

[GerryO]

Hope there something in here that can answer your thermostat location question, but reading things again, I suspect it is his engine thermostat that was sticking.

http://manual.teq.org/MR2_AW_1988_REPAIRMANUAL.zip

You've probably seen this, and I suppose you could run the diagnostic test on both cool and hot days, and they do mention a fluid temperature sensor.

http://z32.wikispaces.com/Automatic+Tra ... iagnostics

Torque Converter Does Not Lock Up
Incorrect throttle sensor or inhibitor switch adjustment,
line pressure or engine RPM signal, faulty revolution sensor or speed
sensor, lock-up solenoid, fluid temperature sensor, control valve
assembly or torque converter.

SHIFT SOLENOID VALVE OPERATION
Application Solenoid “A” Solenoid “B”
1st Gear …………… On ……………………. On
2nd Gear …………… Off …………………… On
3rd Gear …………… Off ………………….. Off
4th Gear …………… On …………………… Off

More info and diagrams here and ignore the document title:

http://www.240edge.com/manuals/89-90_240sx/auto_tra.pdf

http://www.pdfbeast.com/auto-trans-diag ... 314215099/

Good luck!

[GerryO]

From page 34 of the pdf file, the links to which have timed out since I first accessed and down loaded it.

FLUID TEMPERATURE SENSOR TEST
1) Check resistance between fluid temperature sensor
terminals. Resistance should be 2500 ohms at 68 F (20 C), and 300 ohms
at 176 F (80 C). If resistance is not as specified, replace sensor.

2) Disconnect sensor harness connector in engine compartment.
Check resistance between terminals No. 33 and 35 (Infiniti, 240SX and
300ZX), or terminals No. 12 and 15 (Pathfinder and Pickup) when
transmission is cold. Resistance should be approximately 2500 ohms at
68 F (20 C).

3) Check voltage between ATCU terminal No. 33 and ground
(Infiniti, 240SX and 300ZX) or ATCU terminal No. 12 and ground
(Pathfinder and Pickup), while warming up transmission from 68 F
(20 C) to 176 F (80 C). Voltage should be approximately 1.5 volts at
68 F (20 C) and .5 volt at 176 F (80 C). If resistance and voltage is
not as specified, repair circuit as necessary.

[yodawill2000]

if only i knew where the Fluid temp sensor was !
I have suspected it all along.
My dash temp gauge is solid as a rock.

[GerryO]

if only i knew where the Fluid temp sensor was !
I have suspected it all along.
My dash temp gauge is solid as a rock.

Locating the sensor harness connector in the engine compartment, as listed in step 2 might be a good start. It's not obvious why they don't want you to test the resistance across terminals 33 and 35, when things are hot, but maybe they are assuming if the sensor is "good" both cold and hot (step 1), and the harness + sensor is "good" cold (step 2), then the combination should be "good" hot too, which doesn't seem to be a safe assumption in your case.

The two wiring diagrams indicate that '93/'94 sensors have white/red and orange/blue wires connected to them.

[yodawill2000]

Thanks a Ton GerryO

[swimshark]

im actually beginning to wonder if someof the sensors left unconnected with my manual swap are affecting the tune of the car. i need to go through my harness one weekend and do some bypass work.