Codes on the 4runner help!!...rought idlle...

[OzzyNF]

Code 125 "insufficient coolant temp for closed loop fuel control"
I have no idea what this problem is...cooling sensor??

code 141 "o2 sensor heater circuit mailfunction (bank 1 sensor 2)
Is this the 02 sensor in the front of the manifold?

 

[bigtimeweb]

Did you try Google? I did!

Code 125 "insufficient coolant temp for closed loop fuel control"
I have no idea what this problem is...cooling sensor??

OBD-II Trouble Code: P0125 Insufficient Coolant Temperature For Closed Loop Fuel Control

What does that mean?
This means that the engine coolant temperature (ECT) sensor indicates that the engine has not reached the required temperature level to enter closed-loop operation within a specified amount of time after starting the engine.

Symptoms
You will likely not notice any drivability problems.

Causes
A code P0125 may mean that one or more of the following has happened:

* Insufficient warm up time
* Low engine coolant level
* Leaking or stuck open thermostat
* Faulty coolant temperature sensor

Possible Solutions
The simplest thing to do is to reset the code and see if it comes back.

If the code comes back, the problem is likely going to be the result of the above causes (faulty thermostat, faulty ECT sensor, or a low coolant level).

http://www.ricksfreeautorepairadvic...lant-temperature-for-closed-loop-fuel-control

You need to determine whether the engine coolant temperature sensor is telling the truth and the engine really isn’t coming up to operating temperature, or whether the sensor is bad. Many DIYers rush to replace the sensor. And yes, they do go bad. But not nearly as often as the thermostat.

So start your diagnostics by checking coolant level. If it’s low, fill it. Then, using an infra-red thermometer, check the temp around the thermostat housing. At operating temperature, it should be about 195°. If it doesn’t reach that point, you’ve got a thermostat that’s stuck open. A thermostat and gasket is cheaper than a temp sensor.

code 141 "o2 sensor heater circuit mailfunction (bank 1 sensor 2)
Is this the 02 sensor in the front of the manifold?

OBD-II Trouble Code: P0141 Oxygen O2 Sensor Heater Circuit Malfunction (Bank1, Sensor2)

Technical Description
O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)

What does that mean?
This code means that the heated circuit in the oxygen sensor on bank 1 decreases time needed to enter closed loop. As the O2 heater reaches operating temperature, the oxygen sensor responds by switching according to oxygen content of the exhaust surrounding it. The ECM tracks how long it takes for the oxygen sensor to begin switching. It the ECM determines (based on coolant temp) that too much time elapsed before the oxygen sensor began operating properly, it will set P0141. See also: P0135 (Bank 1, Sensor 1).

Symptoms
You will likely notice poor fuel economy the illumination of the Check Engine Light.

Causes
A code P0141 may mean that one or more of the following has happened:

* open or short to ground in the wiring harness
* O2 heater circuit wiring high resistance
* O2 heater element resistance is high
* Internal short or open in the heater element

Note: Typically a failed catalytic converter does not cause this code. You're more likely to see a P0420 code for a failed converter.

Possible Solutions
* Replace oxygen sensor (cannot repair open or short that occurs internally to sensor)
* Repair short or open or high resistance in wiring harness or harness connectors

OXYGEN SENSORS
About everything you could want to know about 02 sensors

 

[brian2sun]

Code 125 "insufficient coolant temp for closed loop fuel control"
I have no idea what this problem is...cooling sensor??

code 141 "o2 sensor heater circuit mailfunction (bank 1 sensor 2)
Is this the 02 sensor in the front of the manifold?

I'm guessing your thermostat is stuck open, the coolant temp sensor is bad, or the o2 sensor is bad - or a combo of any of the 3. There's only one bank as far as the exhaust is concerned (both banks of the engine go to 1 exhaust pipe and then to the O2 sensors/cat), so that particular code is for sensor 2 (rear). That could possibly mean cat problems, but let's not worry about that unless we have to. Here's a good read:
4x4Wire - Tech: Time to Replace the O2 Sensor on your 3rd Gen Toyota?

 

[OzzyNF]

thanks guys i got a new thermostat on the way..i think i will ebay the o2 sensor.

 

[toytech76]

Nope. Your thought process is good but your conclusion to the 125 code isnt right. The o2 sensor is what tells the ecu when the eng isd in closed loop fuel control. When that sensor fails and is stuck in closed loop, after you start your eng when its cold, it sets a code because the coolant temp sensor is saying the eng is cold but the o2 sensor is telling it the fuel sys is already in closed loop. The fault is in the o2 sensor NOT the coolant temp sensor. And by all means, get a denso or ngk o2 sensor. Any other crap will not last

 

[OzzyNF]

ya imo denso is the only way to go.

 

[techno]

For some 4Runner specific info regarding P0125, read this
http://www.ncttora.com/fsm/1996/SIL...2rmsour/2002/024runne/di/eg5vzfe/cip0125o.pdf

For some 4Runner specific info regarding P0141, read this
http://www.ncttora.com/fsm/1996/SIL...02rmsour/2002/024runne/di/eg5vzfe/cip0141.pdf

 

[TheDurk]

Toytech76 has it right. I had the same combo and BOTH were cured by a new O2 (A/F in my case) sensor. So do that first. Notice the FSM P0125 DTC trouble flow chart posted by Techno says do any other DTC codes first.