mmcpeck

Does the coolant temp sensor in the back of the 3VZE control the gauge as well as give info to the ECM, or is there a separate sensor for the gauge?


Thanks.

sb5walker

Two different items, both on the cooling outlet in top center back of engine. ECT, engine coolant temp sensor, tells ecu when motor's reached op temp. Temperature sender just feeds the temp gauge. They look different: the ECT has a plastic connector on top:



...and the gauge sender just has a metal tab:



The other way to know the difference is the price: the ECT costs $15-35 more than the sender.

The naming of them does vary in the catalogs of various parts suppliers, but USUALLY the ECT is called a sensor and the temp gauge sender is called a sender. Check autohausaz.com for Japanese-made sensors that will be cheaper than dealer, probably cheaper than even the online discount dealers.

mmcpeck

Thanks sb5. Would a bad ECT affect the way the engine started at a certain temp?

sb5walker

When the ECT is working properly, the ecu runs the motor in open loop when motor is cold, using preset values for mixture and timing advance and ignoring the O2 sensor. Then when the motor reaches op temp, the resistance of the ECT changes and the ecu switches over to closed loop operation, using the O2 and other sensors to calibrate mixture and timing.

I think usually when the ECT goes bad, it's failing to change resistance when hot so the ecu never gets out of open loop and you get rich running, bad gas mileage, and your cylinders & O2 sensor get gunked up with carbon. But if an ECT were to give the "hot engine" signal when the motor was cold, then the ecu would try to run in closed loop when cold, which probably would run like caca. I doubt that's common, tho. If it's not running right when cold, probably another cause.

If you tell us what's going on, maybe someone could help...