Good-day;

I have a 2001 4Runner with an issue that I have been trying to fix for months. Here are the details:

The engine idles smooth; but at about 2000 RPM, it looses power, backfires, and seems to be very lean. There is an engine code: P0125 - Insufficient coolant temperature for closed loop fuel control.

So, I've replaced the thermostat, spark plugs & wires, timing belt, fuel filter... but the problem still persists. The OBD scanner records the correct temp when the engine is warm; it doesn't seem to be an issue with coolant temperature.

I was wondering if anyone has some input on this; I would really appreciate it. Any ideas at all would be great;

Take care;

 

http://www.ncttora.com/fsm/1996/SIL/...e/cip0125o.pdf

 

Have you changed the coolant temp sensors. Easy and cheap.

 

closed loop means fuel trim try replacing oxygen sensor.

 

Thanks for your responses; I really appreciate it!

The coolant temp sensor seems to be working as the ECU is reporting the correct temperature.

Replace the O2 sensor before the cat, right? I replaced the one after, and replacing this or the Mass Air Flow sensor would be the next thing I would try...

 

So I am assuming that the scanner you are using has live data then if you can read the temp, so what is your long and short term fuel trims reading and what is the freeze frame data when the code sets?

 

Ah Ok; yes it does have freeze frame, here it is:

DTCFRZF P0125
FUELSYS1 CL
LOAD_PCT(%) 31.4
ETC(C) 88 (Celsius)
SHRTFT1(%) -0.8
LONGFT1(%) 0.0
RPM 1528
VSS(Km/h) 59
IAT(C) 16

Thanks everyone for your comments; it's a huge help! I've been trying to figure this out for months...

 

The FUELSYS1 CL means that the engine is up to temp and the computer is going from open to closed loop at around 165F for most Toyota's. The 0.0 Fuel Trim means its not getting a input from the Air/fuel sensor and the high RPM is because the engine thinks it can heat up the sensors to try and get them working. But with no input from the sensor the computer cannot keep the mixture right at the 14:1 ratio so it keeps trying to "guess" which results in the erratic idle and lack of "driveability"

The problem is there's a issue with the P0125 code and Toyota. As the document PDF was posted shows its a upstream 02/Air fuel sensor issue but the title says "insufficant coolant temp".

For some reason Toyota's ODB-II system up to 2002 will throw the P0125 code for a bad O2 sensor when the code by OBD-II standards should mean a stuck thermostat.

The problem is going to be either the upstream 02/Air fuel sensor is worn out or its heater is broken .. both meaning the sensor needs to be replaced.

I would replace then upstream 02/Air fuel sensor and clear the code and you should be good to go.


FOG

 

Thanks everyone for your comments; Going to get a new 02/Air fuel sensor and see how it goes. Thanks again!!

 

what he said