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Engine coolant temp sensor question

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JATBarandgrill

15+ Year Contributor
91
1
Jul 21, 2004
Lincoln, Nebraska
okay, I replaced the main coolant temp sensor unit (the one with two wires) and my car still didnt run well. I checked the codes, it says that the coolant temp fuel is in closed loop. So I rewired it, put a wire from the black w/ white stripe back to the #83 on ecu. Still no go. Anyone have any ideas?

Second, The solid black wire that goes from the ECT sensor, Im guessing its a ground, could this be the culprit? I kept it hooked up to the coolant temp sensor, but maybe its not grounding? Where does it go to?

My stock gauge inside shows that the temperature is where it's suppose to be.
 
JATBarandgrill said:
Second, The solid black wire that goes from the ECT sensor, Im guessing its a ground, could this be the culprit? I kept it hooked up to the coolant temp sensor, but maybe its not grounding? Where does it go to?
It goes to ECU pin 92 (which is a deliberate ground inside the ECU) and also is the return wire for 6 other senders (to pin 92).
 
luv2rallye said:
It goes to ECU pin 92 (which is a deliberate ground inside the ECU) and also is the return wire for 6 other senders (to pin 92).
vfaq says pin 92 is Ignition?
 
Well I'm looking at the real Mitsubishi Service Manual for '99 Eclipse and it shows pin 92 is what I said (p. 90-73). It shows pin 82 is the ignition (p. 90-69) so maybe vfaq has a typo (or 95's have a different ECU than 99's - but unlikely).

It also lists P0125 as "Excessive time to enter closed loop fuel control" and lists "Check items (Remedy)" as O2 sensor (front) or it's harness (p. 13A-25). After O2 sensor (the primary suspect), it lists other things none of which is the coolant or thermostat sensor. Under troubleshooting, it says the engine coolant temp must be higher than 176F before it will do this test and give this code (which I think is the confusion in the non-Mitsu manuals).

I'm just providing the Mitsu info - you can decide. With different engines anything is possible (like it being temp sensors, etc) but if you search the other posts for P0125, you will see the majority have found it to be the O2 sensor.
 
cool, thanks for the info :thumb:

But Im trying to figure out why an O2 sensor would cause it to put in the closed fuel loop. usually it will never limp it like that. Just make it run a little more rich.
 
I believe "Excessive time to enter closed loop fuel control" means it did NOT enter Closed Loop Control (stayed in open loop which is richer). In the "Fail-safe/Backup Function Table" (p. 13A-24) it shows a malfunctioning front O2 sensor results in "Air/fuel ratio closed loop control is not performed".
 
luv2rallye said:
I believe "Excessive time to enter closed loop fuel control" means it did NOT enter Closed Loop Control (stayed in open loop which is richer). In the "Fail-safe/Backup Function Table" (p. 13A-24) it shows a malfunctioning front O2 sensor results in "Air/fuel ratio closed loop control is not performed".


LOL you looked it up for him.
let him atleast get a book.
:thumb:
 
well, I have a fsm, and I cant use it very well. It shows hardly any details, so basically I never even use it. I will replace front O2, thanks. First I need a new turbo.
 
so you replaced the 02 sensor and its still throwing or what? fell us in, i had the same code and i replaced the t-stat and the coolent temp sensor, and finaly the 02 sensor 3 weeks ago and it hasn't showed its ugly light yet.
 
well replacing the o2 sensor did worked for me actually too.....

in the maen while i got the service manual CD and it does say it's the o2 sensor if it throws the P0125.....and has absolutely nothing to do with the thermo or cool tmep sensors...

halik
 
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