1996 3S-GE Coolant Sensors?

[Andrew162]

I've posted in my thread in the Member's Rides with not much help about this issue. Basically it's been plaguing my car for over 4 years, in which time I've replaced the ISCV stepper motor, the full ISCV assembly at great expense, the TPS and now I'm down to individual sensors to try and remedy this thing.

This is what it's doing right now after the ISCV ass'y and TPS changeover (Youtube video link below).

New ISCV at Cold Idle and Warm Idle - YouTube

Since the ISCV changeover, it's actually better than what it was. The TPS changeover did almost nothing. I've searched the toyodiy.com site under ST202 for sensors under 'electrical' and haven't found what I'm looking for. The best it's presented me with is the coolant temperature sender (single pin electrical connection) which takes a reading and sends it to the temperature gauge in the instrument cluster. This works fine, I know because I've disconnected/reconnected and it functions normally at idle and while driving. This is indicated by "1" in the pic below.



Disconnecting "2" means the car won't start, so I'm under the impression that this is the coolant temperature sensor. I've checked the shape and keyways of the plug and verified it is the same as that used in a 5S-FE from a similar year (mid-90's). However "3" I can't figure out what it is. It is plugged into the same coolant "tap" as the other sensor and sender but I can't find any relevant info on this, and all searches lead me back to the one item, which Google automatically thinks is the coolant temperature sensor, when it's actually the sender instead.

So this is a bit of a plea for clarification on exactly what is what on this water/coolant tap. I don't have a BGB to refer to and as I mentioned above, toyodiy.com seems to be limited in it's facility of descriptiveness, or I'm limited in finding the right sensor which could be listed in any other sub-section. For reference, the sender part number is 83420-16040. I have one of these ready for replacement, just in case.

As usual, any help appreciated.

[Dazza]

Does it have a cold start injector. The ST162 has the cold start timer switch in that spot. 2 would be the coolant temp sensor for the ecu. 1 is for the temp gauge. The ST162 also has a temp sensor on the thermostat housing for the thermo fans.

[jonathan yee]

I ll need to check my bgb, but number 3 doesnt look like a gen3 sensor. Is it possible its the st162 temp sensor for the fan? Normally in the thermostat housing? Or bottom of rad?

[Andrew162]

1996 3S-GE is a Gen 3 which has no CSI.

I thought it might have been a sensor for the fan, makes sense.

I'm hoping by changing over the right sensor it'll improve the attitude of the car's warm-up phase.

[Dan_k36]

I'm thinking its a fan switch, pull it off, turn key on and see if the fans run non stop, that'll tell you

[Andrew162]

Now I have a replacement ECU coolant sensor and I'm trying to track down the fan switch for the radiator and the other switch "3" for the coolant tap. I don't care if I replace all of them I want this problem solved.

[thechuckster]

On the hot outlet there are 3 or 4 sensors, ecu temp (2 pins), cold start time injector (2 pins), gauge temp sender (1 pin) & a/c controller temp sender (1 pin).

[Andrew162]

Hey chuck, I've verified that #1 is the sender, #2 is the sensor for the ECU, and #3 is thermo fan switch. Although it's an ST162 there's no cold start injector on this engine.

[Andrew162]

Just a quick follow up on this, I got a link for a video which is uploading atm which explains what's going on now after the sender/sensor/switch have all been replaced.

I'm thinking its a fan switch, pull it off, turn key on and see if the fans run non stop, that'll tell you

When I shot this vid, an intermittent issue came up where the rad fan (the engine bay side / pull fan) came on upon turning the key to ignition. It's still unknown as to why this happens and until recently I couldn't find the fan connector because it was hiding under the A/C relay box. My understanding is it's the stock ST162 fan connector leading into a loom past the A/C relay box and I can't find any other fan switches as yet. According to the toyodiy.com site there should be a thermofan switch in the bottom-right of the radiator (from the front of the car), but mine has nothing there, nor in the thermostat housing.

Anyway the lumpy idle seems noticeably reduced and it doesn't want to idle more than ~2000rpm before it starts hunting, and then settles into a temporary high idle of between 1700-1500rpm for a couple of minutes. This could also be weather-conditional, today it was rather warm and it can do the idle-hunting more on a cooler day.

Anyway here's the recently uploaded vid...
http://youtu.be/ROKReBPhDSU