CHTS question

[rickyellow zee]

 At idle if I unplug my CHTS on my L28ET swapped 280z there is no difference at all. I read somewhere that the car should bog down when the CHTS is unplugged. Mine does not. From what i understand by reading the fsm the ecu reads the chts all the time. Correct?

 

I checked for continuity between the CHTS plug (which is new) and ECU plug and continuity does exist. I also tested the sensor itself according to the fsm and Im getting the right numbers. Maybe my issue lies in the ecu connectors not mating properly with the ecu? I tried wiggling them as the car idles and no difference. The car as it is runs rich.

Thanks.

[NewZed]

Check for continuity to ground on the other side of the connection at the CHTS.  The ECU sends a voltage out that passes through the CHTS on its way to ground.  One pin to the ECU, the other to ground.  No ground is like no CHTS.

[rickyellow zee]

Gotcha. Will try that when I get home soon. Thanks

[rickyellow zee]

So I wanna be clear. The chts has 2 wires. One wire (Yellow/green) which goes to ecu plug slot 23. I checked and got continuity. The other wire(black) goes to ecu plug slot 26.  Continuity exists as well. Is this what you mean when you say to check the ground?

 Thanks again.

[NewZed]

That's one way.  The ECCS system probably runs the CHTS ground through the ECU.  The better way to confirm that the ECU is getting what it needs though, would be to measure resistance to ground at the ECU plug and compare the resistance to the temperature versus resistance chart in the FSM.  Continuity doesn't really tell you much.  Study the diagram for the ECCS ECU and you'll probably be able to figure out which pin is ground and which is the temperature circuit.  Check resistance of your other ECU grounds while you're in there, you might have high resistance on the main ground circuit which is giving high readings from the CHTS.

Edited June 9, 2014 by NewZed

[BitchinZ]

What was your resistance reading on your CHTS?  I have one reading around 1600ohms and another reading 1400 ohms.

[NewZed]

The curve is steep and not super accurate.

[cgsheen]

Pull the plug on the CHTS and check the resistance again. (Use the 20K Ohm scale on your multimeter)  Plug it back in.  Go to the ECU plug. Check the resistance between pin 23 and pin 26 - should be fairly close to the resistance value you just measured at the CHTS.  If it's not, you have a wiring problem.

 

Back to basics:

The CHTS is a "thermistor" - a resistor who's value changes with heat.  At about 70 degrees F it should read close to 2.5K Ohms.  (Look at the scale in the FSM - @ 68F value should be 2.1-2.9K Ohms)  The resistance value will drop with heat, rise as it cools.  At operating temp it should be close to 0.3K Ohms.  If your CHTS isn't giving you the same "temperature vs. resistance" numbers that the FSM chart shows, you have a sensor problem.

 

@Bitchin...  Those values would be about right if the ambient (or sensor) temp was ~95-100 degrees or so.  Warm up there? 

[rickyellow zee]

So I checked the resistance at the sensor and at the ecu plug. The same at 2.36 ohms. Right on the money according to the schematics. I did a continuity check between the chts black wire and the afm black wire as they are spliced together as per the wiring diagram and continuity exists. Everything so far is spot on. Why does it make no difference when I unplug the chts at idle? The car behaves the same with or without the sensor plugged in. At this point Im almost certain its the ecu plug not mating well with the ecu.