Coolant gauge pegged above H, but not overheating.

Hey everyone.

I am new to the Tacoma world, just bought an 04 Toyota Tacoma, 4 door with the V6 3.4L Engine. My issue is when I first start the engine in the morning, cold start, temp gauge on the dash shows cold like it should. However after 1-2 minutes of warming up, will spike up above the H and stay there. However the engine is not over heating, everything working as it should, and not getting incredibly hot. Im assuming this is a bad temp sensor? I've found there are two, one on the front, which goes to the comp, and the one on the back that goes to the gauge. Had our electrician tech at work test the sensor and the ohms steadily declined until it ultimately hit zero. He was expecting it to just drop to zero at some point, since the gauge jumps from C to H. But it didn't, however it still hits 0 even though it is not over heating. Am I looking at a bad sensor here? Just don't want it to be a bad gauge because that involve the dash cluster. Any advice is helpful. Thanks!

 

Welcome!

Not with my Tacoma but I had this issue long ago with a car. The temp sensor did the trick

 

I’d say most likely the sensor. I had a similar prob on a Ford truck and it was the sensor.

 

Another vote for the sensor. Was pretty cheap on a Mazda I used to own, and easy to change.

 

Okay so I have replace both sensors. The ECT at the front of the engine, and the gauge sensor at the back. Temp gauge still climbs up to H after 2-3 min on a cold start. Engine still runs fine, no steam, no fan running overtime. Bad gauge or resistor in the gauge?

 

I would check the wiring to the cluster. Are the other gauges behaving?

 

Cheap Chinese sensor.

 

Yea Fuel, speedo and tach all working as they should.

 

If you have a multimeter, I would check what voltages you're getting at the sensor. There should be a spec somewhere.

 

I do have CEL on and its throwing code P0118 "Engine Coolant Temperature Circuit High Input". But you would think switching both sensors would fix that. Unless its something in the harness not connected?

Me and a buddy ran the coolant temp on his OBDII and its sitting at the correct temp, so definitely not overheating.