Plain Jane OEM nothing to see here rebuild

[JL1RX7]

Originally Posted by Pete_89T2

The problem with doing it that way is your DVM/ohmmeter puts some voltage across the terminals you're trying to measure a resistance across. If it's still connected to the ECU with power applied you could potentially harm the ECU. Also, unless you have a good aftermarket temp gauge, how will you know the water temp when you're taking the resistance measurement?

Assuming you do have a temp gauge, one option would be to run the car until warmed up, then jot down the water temp off the gauge and shut it down. Disconnect the battery. Then disconnect the ECU connectors, and do your resistance measurement across the two ECU harness connector pins that connect to the water temp sensor. That will only get you one test sample though, so you still won't know if the temp sensor works across its full range. IIRC, the FSM gives 3~4 temp points to measure resistance on that temp sensor.

If its a RTD or resistance temp device it should have table somewhere about the resistance readings. So say 1k ohm means 72 degrees. Wouldn't really matter if you got multiple readings as long as you get a good resistance reading.

Also resistance will determine your voltage. So if your TPS has a "dead spot" it won't matter if you're reading voltage or resistance. One you when off, the when on.

[JustJeff]

Originally Posted by Pete_89T2

The problem with doing it that way is your DVM/ohmmeter puts some voltage across the terminals you're trying to measure a resistance across. If it's still connected to the ECU with power applied you could potentially harm the ECU. Also, unless you have a good aftermarket temp gauge, how will you know the water temp when you're taking the resistance measurement?

Assuming you do have a temp gauge, one option would be to run the car until warmed up, then jot down the water temp off the gauge and shut it down. Disconnect the battery. Then disconnect the ECU connectors, and do your resistance measurement across the two ECU harness connector pins that connect to the water temp sensor. That will only get you one test sample though, so you still won't know if the temp sensor works across its full range. IIRC, the FSM gives 3~4 temp points to measure resistance on that temp sensor.

Yes I have an aftermarket temp gauge, a Prosport, which isn't name brand, but it' seems to be about dead on. The sender for the temp gauge is tapped into the front of the water pump housing and is taking a reading at the same spot the OEM thermosensor is.

I also have a temp gun I could point at the water pump housing, radiator, hose, etc.

I was thinking the same thing about taking multiple readings, per FSM. I could test as the engine is warming up. Turn off the engine at each temp test and continue to the next....ugh but that means taking the UIM off each time to get to the thermosensor harness.

Originally Posted by vrracing

Our RTek 2 shows the temperature reading from the ECU on the Palm. Does the 1.7 not have that capability?

No logging on Rtek till you get to 2

Originally Posted by JL1RX7

If its a RTD or resistance temp device it should have table somewhere about the resistance readings. So say 1k ohm means 72 degrees. Wouldn't really matter if you got multiple readings as long as you get a good resistance reading.

Also resistance will determine your voltage. So if your TPS has a "dead spot" it won't matter if you're reading voltage or resistance. One you when off, the when on.

The FSM has 3 temps to take resistances at and what the corresponding resistance should be, but not really a full scale that I know of. I suppose I could take resistance readings when they are at the resistances for a specific temp (per FSM) check the temp of the coolant to see if they line up.

With the TPS, yes we are kinda saying the same thing...I was more round about. But laws of electricity say that if there is a dead spot in voltage test there will be one for resistance also. I meant something is amiss, as in it wasn't tested correctly..not probed correctly and such.

[Pete_89T2]

Originally Posted by JustJeff

Yes I have an aftermarket temp gauge, a Prosport, which isn't name brand, but it' seems to be about dead on. The sender for the temp gauge is tapped into the front of the water pump housing and is taking a reading at the same spot the OEM thermosensor is.

I also have a temp gun I could point at the water pump housing, radiator, hose, etc.

I was thinking the same thing about taking multiple readings, per FSM. I could test as the engine is warming up. Turn off the engine at each temp test and continue to the next....ugh but that means taking the UIM off each time to get to the thermosensor harness.

Don't need to take the UIM off... What I was suggesting in my previous post is you take your readings off of the 2 water temp sensor pins on the ECU connector, after disconnecting it from the ECU. BTW, the resistance reading you'll get this way will be a little higher than what the FSM states for the temp sensor, but it shouldn't be by much more than a few ohms. This is because you're also measuring harness cable losses to the sensor.

[JustJeff]

Originally Posted by Pete_89T2

Don't need to take the UIM off... What I was suggesting in my previous post is you take your readings off of the 2 water temp sensor pins on the ECU connector, after disconnecting it from the ECU. BTW, the resistance reading you'll get this way will be a little higher than what the FSM states for the temp sensor, but it shouldn't be by much more than a few ohms. This is because you're also measuring harness cable losses to the sensor.

Forgive my ignorance, but I'm confused on how you're talking about testing resistance. IIRC the harness at the sensor is 2-pin. So to test resistance between those two pins wouldn't I need to find out which pin on the sensor harness corresponds to the ECU pin and then test resistance between that pin and the other pin on the sensor it'self?

I'm confused on what 2 pins on the ECU I'd be testing for resistance. 2E is the only water thermosensor pin on the harness/ECU. I originally was thinking I could put one DMM probe on that pin and one ground to chasis...but that's not the same as checking resistance at the sensor itself...or is it and I've simply overthought things and gotten myself confused.

For what it's worth, I was thinking the same thing about added resistance for the small load the harness will add.

[Pete_89T2]

Originally Posted by JustJeff

Forgive my ignorance, but I'm confused on how you're talking about testing resistance. IIRC the harness at the sensor is 2-pin. So to test resistance between those two pins wouldn't I need to find out which pin on the sensor harness corresponds to the ECU pin and then test resistance between that pin and the other pin on the sensor it'self?

I'm confused on what 2 pins on the ECU I'd be testing for resistance. 2E is the only water thermosensor pin on the harness/ECU. I originally was thinking I could put one DMM probe on that pin and one ground to chasis...but that's not the same as checking resistance at the sensor itself...or is it and I've simply overthought things and gotten myself confused.

For what it's worth, I was thinking the same thing about added resistance for the small load the harness will add.

My bad, I should have given you the reference to the schematic diagram on FSM page F2-8. If you follow the water thermo sensor wires back to the ECU connector on the diagram, you'll see you can measure your resistance between pins #2E and 3D. Pin 2E goes to the water thermo sensor and connects to nothing else; 3D is labeled "E2" on the ECU side, which I believe is a common +5VDC supply to a bunch of the sensors, including the water thermo.