Engine Coolant Temp.(ECT) Sensor Question

[Ed Calvert]

I have a question for someone smarter than me about the ECT sensor. Does the PCM use the sensor for anything else besides just turning on the electric fan? The reason I'm asking is that I was able to rig up a potentiometer/toggle switch combination mounted in a small plastic box with the wires going to the ECT connector. With this set-up I've been able to fool the PCM into thinking that the engine coolant is hotter than it really is and it turns on the fan. I've tweeked it for about 195*. It seems to work pretty good. I'm just not sure if the PCM uses that sensor for anything else. You know, fix one thing then screw up another.
Thanks for any inputs.

 

[swingline]

It has a lot to do with regulating A/F and timing.

 

[jmuva44]

As long as it is getting fairly accurate information, everything should be fine.

 

[MLC Stang]

Ed,

The ECT is one of two sensors that the PCM uses to determine proper Air/Fuel ratios for various engine operating temperatures.

If you defeat the range of input signals that the ECT can send to the PCM, then your A/F ratios will be wrong for your engine's operating temperatures at some point in the range.

If you flip that switch to tell the PCM the engine is hotter than it really is, the A/F ratio will be leaned out when it shouldn't be. This may result in your engine running poorly or even pinging if the ratio is leaned out enough.

Take the switch out, and let the ECT do its job properly.

If you have a cooling fan on/off issue, it is most likely related to the CCRM (Contsant Control Relay Module) that contains the fuel pump and cooling fan relays.

Fix the real problem, don't "fix" the symtoms by defeating another control system that the engine needs to run right.

 

[jmuva44]

I agree, if you want the fan to come on earlier, get a fan controller or adjust the settings in the ECU. Or get a new ECT sensor if you think the one you have isnt working like it should.

Most people would throw a new radiator (ie: Fludyne) iat the car to fix the overheating. But the problem will still be there. Fix the problem first.

 

[Ed Calvert]

Yep, OK, you guys answered my question and your right. I think the cooling system is working per spec. eg. the thermostat opens up at about 180-190* and the cooling fan cuts on at about 210* or so. This is probably about right. I was simply trying to have the thing run a little cooler in stop and go traffic. I do get some pinging under load as well, even with high test gas. timing is 12*BTDC with underdive pulleys. Perhaps I'll just put a switch on the fan and not play with the sensors.
thanks!!

 

[baskin]

Ed, the only problem with your solution is that for a small change of high temp calibration on the ect, you're creating a huge change in the low temp calibration. I'll be offering an ect recalibration module in a couple of weeks which only recalibrates the higher temps. It also keeps the car from going open loop when lowering the thermostat. I have the working prototype if you want it. (the only difference between this and the production units is that this one is initally set at -10degree offset with a jumper for -20, the prod unit uses a potentiometer to adj. the temp.) It's not worth writing up a second set of instruction sheets needed to sell it, so it's free. E-mail me through the site if you're interested

www.dccontrol.com

http://www.dccontrol.com/adjusted_temperatures_for_ect_op.htm