Thread: Question about O2 sensor and coolant temp sensor

Hey, I've got a bluebird with T25, I'm running a JWT ecu (4bar, 370's, bored MAF etc), but I'm having an issue with the radiator fans coming on. Thermostat is working.

I'm wondering what kind of CTS I need to be using for this ECU, as well as what kind of O2 sensor (the front one). The dash temp gauge stays maxed out, but my auto meter gauge stays around 190-200. I've tried swapping both wires on the actual temp sensor, but same result.

I've been out of the game for a minute, so I'm sure it could be something simple I'm overlooking.

For an o2 sensor, you wanna run that fat usdm one that originally came in the car. As for the coolant temp sensor, that should also be the oem one that came in the car. If thats what your running, try replacing it, its cheap. I think I paid like 25 bucks for it a year ago.

This is assuming you have a usdm wire harness which you probably do if your car is an se-r

Cool, thanks. I'm going to replace both of them, should be about $100.

I was talking to a very knowledgeable guy at the shop today, and he said that all O2 sensors are the same, the only difference is the length of the actual case, the length of the wires, and the connector to the harness, but I'm going to go on and replace it.

There are two sensors for coolant too, one for the gauge, and one for the ecu (that controls the fans). The single wire one is for the gauge, the two wire one is for the ecu.

Yes, that' correct. If I were to have one of the wires for the sensor hooked up to the gauge, would this cause it to peg out?

I'm not sure I understand your question. If you had a bad or wrong gauge sending unit then it would possibly peg out the gauge; this would be the one wire sensor. Can you rephrase your question?

If you short out the two wire sensor with a paperclip or something then it should kick the fans on, if that happens I'd bet you had a bad ecu temp sensor (the two wire one).
Ps is this a b13 or b14?

Thanks. This is on a B14. I'll try to short out the wires and see what happens.

When I got the car, the connectors were all cut off of the wires, so I just kinda guess which ones went where. I was wondering if I had put one of the wires that was supposed to go to the actual temp sensor on the dash gauge sender, would it cause the dash gauge to peg out? See what I'm saying?

Get a copy of a Fsm, haynes, or chiltons and make sure the correct wires are going to the correct place. Once again if you have the wrong temp sensors this will mess things up too.

TAke a look here, study the el section.
http://www.nicoclub.com/FSM/Sentra/1996/