Recently got a 2001 Honda Accord EX V6 (J30A1) with 115k miles.
Been driving it daily for a week now, and yesterday all of a sudden while on the highway cruising at 70mph the temp gauge was climbing up .
I slowed down to about 60mph and the temp raised to almost red. Then it when back down the middle abruptly. The temp gauge was fluctuating from middle to almost red several times.
When i got off the highway I immediately stopped and hooked my OBD2 Bluetooth to Torque app and saw my temp was at 240 degrees with real time information. Let the car sit for a few minutes turned it back on and the temp was 180 the rest of the ride home (about 15 mins.)

I cant seem to find any info on the V6 J30, on how to test the fan switch(s).
I found online the 4cly that you can jump the ECT with a paper clip but what one is it on the V6?
Does anyone have a diagram ?
Is it the one on the thermostat housing?

I'm thinking about just replacing the Tstat and ECT at the same time since they both look original and they are like $30 each... just wanted to diagnose for sure that one of them is the culprit.

 

Check the coolant level in the radiator. Usually when you're driving on the highway at 70 mph, the air flow should help cool the engine where it shouldn't overheat.

Turn on the A/C, does both cooling fans run?

You can also unplug the connector to radiator fan switch A (located on thermostat housing) and jump the connector with a wire or small paper clip. Both cooling fans should run with the ignition in the ON position.

 

I would second that you are low on coolant. The up and down is the fluid insufficiently flowing.

it's possibly you have a clog or a bad water pump, but I would check fluid first.

 

Thanks for the info. I checked the radiator, and over flow tank and are full. Took the car for a 30 min drive and it did it again. When I got home I popped the hood, no fans on (a/c off) top hose was warm bottom hose was warm rad cap was slightly warm. Nothing seemed over heated? I plugged in the OBD2 and saw the temp was over 300 degrees! I also checked the fans by placing the ignition to II and turn on a/c , and fans came on. Also jumped the ETC on the thermostat house and they came on as well.
What sensor is hooked up to the temp gauge? Is it possible to have 330 degree to the temp gauge but the radiator, hoses and thermostat just feel warm? Think the TStat is messed up? I ordered up a new Tstat and ECT for now...

 

On a 2001 Accord V6, the temperature gauge gets its signal from the PCM, via the ECT sensor. The PCM controls the magnetic field generated by the ECT sensor by varying the current to the gauge.

 

The ECT in the above pic is not the same as the one on the thermostat housing? I ordered the one on the TStat housing and the Tstat.
Do you have a part# for that sensor. I might as well replace that too all at once...
How can I test that ECT above? Can I unplugg with engine running to see if the signal changes, or is there another way?
I'm assuming that might be the culprit because if that's what's hooked up to the temp gauge and showing the OBDII output 330 degrees then that may be going bad?

 

The ECT sensor is different than radiator fan switch A. ECT sensor is # 15 in the parts diagram (Honda part #37870-PK2-015). Radiator fan switch is # 14 in parts diagram (Honda part #37760-P00-003).

There is no specified test for the ECT sensor in the service manual.




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Radiator fan switch A (a normally open switch), closes at approximately 199 degrees F, which should send the ground signal to activate both cooling fans.

 

Awesome information. Thanks so much for the diagram too.
I found this one, (see pic) in stock at Auto Zone, looks like the correct one so I'll swap it out. You think that ETC could be the culprit for my crazy temp issue like the 330 degree and temp gauge fluctuations?

 

It is possible. Let us know how things turn out.