Hey all I'm just needing a bit of help with my car I have an 06 Lancer with the 2.4, engine light comes on and when scanned it produces P0125 excessive time cooling loop fuel system code twice as two separate entries which is weird. Now here's where I'm stumped. I've completely replaced everything to do with the cooling system, has new water pump, thermostat, new ECT sensor, new radiator hoses and new coolant as well, timing belts have been replaced as well and even after replacing everything this light and code will still show up and stay on until cleared with an obd2 tool, once cleared it takes 2 days of driving it for the light and code to reappear. I have tried everything and nothing has fixed it. Please note that the car is driving beautifully so I don't get why it's happening, it's not overheating and my fuel economy isn't affected either I still get 600-700km out of a tank. Any suggestions would be fantastic!

 

Just a quick update I've checked the voltage of the power going through the wiring to the ECT sensor, minimum at normal operating temp is 0.03v to 0.09, mine reads 0.01 so not getting enough voltage to it. How can I fix that so it gets the proper voltage so the engine light doesn't come on and throw P0125 at me?

 

@Joshua Bayada Your ECT wiring harness is damaged. Voltage is supplied by the ECU to pin 1 of the ECT connector (yellow/white wire) and should read between 4.5 - 4.9 V with key on. You must trace the wire back through the engine bay harness to find the break and fix ir. The best way to do this is to get a copy of the manual and then use the wiring diagram (pg. 90-51) to trace the connections back to the ECU. The yellow/white ECT wire goes direct to pin 83 on the ECU (C-129 - 22 pin yellow connector). It runs in the main engine harness through the firewall to the ECU. If you cannot find the break in the wire, run a new wire from pin 83 direct to the sensor.

 

Cheers for that info, really appreciate it. Turns out i had the multimeter on the wrong setting, I'm still learning how to use one. Voltage reads correctly now however I'm still stumped to what's causing the problem as everything is new and has been replaced/renewed. Something has to be wrong with the electrics as it's killing amplifiers and speakers as well lately

 

@Joshua Bayada OK let's start with the basics:

1. Not enough coolant or air lock in the system?
Pull the radiator cap (when the engine is cool) and look for coolant - it should be up to the cap. Check the overflow tank - coolant should be up to the fill line. Did you "burp" the system when you refilled it? If not you may have an airlock in the thermostat housing. In either case there may not be enough coolant for the ECT sensor to read its temperature causing the P0125 code. The engine can be really hot, even though the ECT sensor is reading low temps. If the coolant level reads bone dry, don’t fill it up when the engine is hot. Let it cool down first. Introducing coolant to an engine that is overheating can badly damage the block or head.

2. Thermostat stuck open?
If the coolant level is fine, your thermostat may be stuck open. When this happens coolant is always cycling through your radiator. This may keep the engine cooler than it needs to be, especially now the weather is getting colder. If the coolant temperature is lees than required for closed loop fuel control, this will trigger the P0125 code. Pull your thermostat again and check it is operating correctly using the procedure in the Factory Service Manual.

3. Cooling Fan Stuck On
If the fan is running when it is not needed, it can over cool the engine and it can’t get to the temperature that it needs to run at. This is usually caused by a bad fan controller. Use the troubleshooting procedure in the FSM to test the controller.

4. Bad ECT Sensor
I know you have already replaced the sensor, but if you have eliminated all the previous things, including the wiring, then the new sensor may also be bad. If you have confirmed that the voltage supplied to the ECT is correct, remove it from the thermostat housing and verify its resistance at different temps using a bowl of water/ice. Its resistance should be just a few hundred ohms in boiling water, and 5-10 thousand ohms in ice. If this is not the case get another sensor.

Good luck with your troubleshooting!

 

Coolant level is good, i did burp the system when i put new coolant in after replacing the water pump and thermostat. Thermostat doesn't appear to stay open. I went to work yesterday and monitored the temperature with my obd2 tool and sat around 90ish degrees C, i replaced ect sensor as i thought that may have been the problem, fans aren't stuck on. It's really got me stumped. It takes a couple days of driving for it to come back with the engine light and that code which is weird. I'll check the resistance of the sensor and see what it reads. I'll check thermostat as well. Appreciate the help our weather here is getting hotter heading into summer. If there was a problem you'd think the light and code would be instant but takes a few drives for it to come on haha

 

@Joshua Bayada Which sensor did you replace? The dash temp gauge has its own sensor on the side of the T-stat housing (1). Temp sensor for engine (2) is entirely different, it is on the front side of the T-stat housing




The ECU process that monitors and sets the P0125 code happens during a 10 minute drive cycle as follows:


DTC SET CONDITIONS
Criteria used to set P0125 which are monitored during the drive cycle:
• Engine coolant temperature decreases from higher than 40°C (104°F) to lower than 40°C (104°F), and the engine coolant temperature then continues to be 40°C (104°F) or lower for five minutes.
• Engine coolant temperature fails to rise to about 7°C (44.6°F) during 60 − 300 seconds after start up.

Attached is the full P0125 diagnostic procedure from the Evo 8 FSM as I can't find anything in the Lancer FSM. I think the ECT sensor is the same between models so the bulk of this applies. ECU pin numbers and connector numbers will be different. This should give you what you need to find the root cause.

BTW - Are you in Rutherford NSW?

 

I replaced the Ect sensor by the thermostat. I'm not in Rutherford nor NSW. Engine light would come on every 4th drive after clearing the code. Hasn't come back yet so maybe it's sorted hopefully lol

 

So to confirm, you replaced sensor (2) on the front of the thermostat housing right?

 

It's by the hose that goes to and from the thermostat yeah

 

Just got to work and the light came back with the same code. I really don't understand what is going on as everything is new. It's getting frustrating lol

 

Thing is though why does it take a few days to bring the light up with the error code?

 

@Joshua Bayada Now you know all the temperature sensor inputs are working correctly let's look at two other possibilities:
1. Has either your front O2 or rear O2 sensor failed? You can check by using your OBD-II reader to monitor the O2 sensor voltages during warm up. They should both start to swing between 0-1V, showing that your ECU is operating in closed loop once coolant temp goes above about 30 deg C. If one or other O2 sensor's voltage is not moving, your ECU can throw P0125.
2. Has your ECU ROM been tuned? If the rear O2 sensor has been turned off in the tune that can also trigger a P0125. You will need a Tactrix cable and ECUFlash to open your ROM and look at the ECU Periphery FAA bit settings. Bit 01 for the Rear O2 sensor must be set to 1 to prevent a P0125.

 

My O2 sensors appear to be ok. ECU was tuned several months ago but both o2 sensors show up and operating. I plan to invest in a tactrix cable eventually but wouldn't touch anything as i don't want to screw the car up lol. At this stage I'm thinking it's either thermostat or the coolant or even both that's the issue. I'll have a bigger thermostat come in work Tuesday from another store. The thermostat i put in i had bought ages ago and is just a standard one. The one that was in the car when i bought the car was a bigger high flow one so am thinking it needs the high flow one but coolant may also be the issue as it's non glycol where as it specifies glycol Type A coolant not tybe B non glycol so could be the issue as it must warm up differently. That's all that's left I can try really, it's beyond me what's up with it lmao

 

@Joshua Bayada If both your O2 sensors are cycling then you are definitely in closed loop. Your tuner may have set the rear O2 sensor off in the FAA periphery settings which is known to cause P0125. The high flow thermostats open sooner (at a lower temp) in the warm up cycle, and would only cause this problem in winter by over cooling. The standard thermostat will not cause a P0125. The difference between coolant types A & B won't affect the warm up time or the operating temperature that much. When P0125 is thrown, the ECU assumes a fail safe coolant temp of 80 deg C and keeps operating correctly so it won't do any harm.

Once you get your Tactrix pull your ROM, post it up, and let us know if you need more help to check the FAA settings.