A little Tech help, please

[datrupr]

A little background first. This happened the first time in August coming back from Sedona, cleared the code and it never came back, until this weekend. The same type scenario when the trouble code popped up. The code I'm getting is P0125 "Insufficient coolant temperature for closed loop fuel control". All three times the code popped up was when I was pulling a grade and trying to maintain speed. The transmission downshifts and I will run for a bit at about 3500 RPM, and the code triggers. There is no effect on the driveability of the truck. The engine runs and sounds normal, the transmission shifts normal, and the temp is in the normal range. Now, This past weekend it happened again going to San Diego. It was parked most of the weekend, but on Sunday I went to O'Reilly to read the code (the guy there told me that in California they can't loan out the OBD readers so I would have to buy one). Anyway, I was a little upset, got back in the truck, started it and the code SES light was off. Going home, pulling the grade the code came up again and again no actual signs of trouble. When I got home I pulled the code but didn't clear it, and again it went away on it's own. So, what is causing this code only when I am pulling a grade in a lower gear? Is it my thermostat? After 4 ignition cycles in normal city driving the range goes back to normal and the code clears itself. Any help on this would be appreciated. Also, this is an '01 Montero 3.5 with the INVECS II 4 speed transmission. Thanks in advance.

 

[off-roader]

I'm not sure what exactly triggers that code but I'm assuming it occurs when the engine temp gets too high? If so, perhaps the transmission temp is also getting high, causing your engine's radiator to cool less efficiently?

If this is the proper course of thinking then my suggestion would be to check your transmission fluid. It's possible that it's dirty creating a clog in the separate tranny radiator therefore raising the tranny temp. Yes it's a long shot but you can check it by checking your engine temps.

Alternatively it's also possible that your engine is running hot on it's own having nothing to do with the transmission temps.

Also, I'm surprised to hear that they're no longer loaning code readers in California. Did you try to get one from another parts store like Autozone or Pep Boys? That said, OBDII readers are pretty cheap especially the basic ones and worth owning IMHO. I have a basic Accton unit I keep in my rig.

 

[datrupr]

I don't think its running hot, the transmission or the engine. The fluid is fine, I had the transmission serviced not even 1,000 miles ago with new fluid and filter. I checked the fluid after the code came up and no signs of dirt or burning. If anything, I thinkthe code is saying the engine is too cold. But I have no idea. I am now a proud owner of and OBDII scannner because of the ***hat at O'Reilly's in Point Loma. I think he was just to lazy to get it out and let me borrow it. Anyway, the code has gone away on it's own again. I am wondering if the thermostat is maybe staying open too long when the RPM's are high causing the code? Other than the code, there are no other indications of anything wrong. It still runs normally, shifts normally, idles normally, and the temp guage is reading normal, and there is no loss of power (not that there is a lot ot begin with). I don't get it.

 

[Justice R]

Cooling

I agree that the computer is telling you it is running too cold. Do you know when the T-Stat was last changed? It may be stuck open or at least partially open. I recommend replacing with an OEM T-Stat. The OEM is way beefier than aftermarket. One other Item to check would be the CTS (coolant temperature sensor) that sends the signal to the ECU letting it know the temp of the coolant. I would start with a new thermostat, and then take it from there.

Replacing the T-stat is part of the regular maint schedule so its a good Idea to replace if last replacement interval is unknown.

 

[datrupr]

I went through my maintenance records and could not find when the T-stat was last replaced. Looks like I have a call to the dealership to make as this problem will only get worse if it is the T-stat. Thanks for the help guyus, I'll keep you all posted.