P0125 error code - help! (2 Viewers)

[Olaf]

Got this discussion started looking into replacing my fan clutch and overheating.

To recap I've done the following:
New denso o2 sensors 1'12, toyo tstat 3'12, ect sensor 3'12, new head gasket 4'12, radiator 1'11, truck 307,000 miles, new belt and replaced hoses 7'12, new blue hub fan clutch with 20k silicon.

get's hot, up to red on factory gauge, 210 F on ultra gauge pulling a load and on highway for 2hours at 80mph. In traffic and on highway, when o/s temp is in the 90's truck runs 188-205 F. Mileage around 12mpg

I'm thinking radiator or waterpump?

Any thoughts?

 

[doc W]

Am thinking here that 210 is not that bad for pulling a load at 80 mph. You say you run 188-205 in traffic and on highway this is within range but the 12 mpg seems a little low.

On a hot (mid 90s day) grinding up a logging road with the air on full I run in the 190's. Ditto on the highway climbing a grade. This with new radiator and Tstat. Water pumps rarely go south.

Me bad did not notice the error code! "P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control". Not sure what that means.

Good luck with it. I presume you looked in the FSM. Quite a procedure to check it out. Hopefully some expert will chime in.

 

[94SRUNNER]

So, what other coolant system maintenance have you done?

The radiator you replaced a year in a half ago, was it an aftermarket unit or a factory unit? What makes you think you need to place it agian?

Water pumps rarely seem to go out on these trucks.

The code you have is for the ECT - engine coolant temperture sensor. Did you replace with a factory unit or an aftermarket unit? I would first test the sensor per the FSM to see if it is function properly.

 

[Olaf]

Good points. All new fluid radiator appears full. Changed out in July. What temp is too high. Factory gauge in red at 210. Radiator is aftermarket and so is the sensor. Thought radiator might be bad because getting into red on gauge and p0125 code.

 

[94SRUNNER]

I believe the AC cuts out at something like 215-220, I could be off slightly...nothing a search wouldn't yield.

One thing that could be happening is there could be air trapped in the system. Park it on an incline, remove the radiator cap, start up the truck and allow it to get warm. While running turn on the heat to high and turn on the rear heat as well so that any trapped air can move through the system and escape out the radiator opening. Try this first before replacing anymore parts.

I would however take a close look at the ECT sensor. Test it and comfirm it is functioning.

What fan clutch do you have?

 

[Kernal]

Did a search for P0125 and came up with this (below):

P0125: Insufficient Collant temp. for Closed Loop fuel control: Trouble Areas: Open or short in heated oxygen sensor circuit; heated oxygen sensor.

P0125
The PCM has determined that the amount of time it took for hte coolant temperature sensor to reach an input value consistent with the closed loop operation was too excessive.

https://forum.ih8mud.com/80-series-tech/117788-holy-codes.html

https://forum.ih8mud.com/80-series-tech/174812-need-rth-p0125-code-wont-go-away.html

https://forum.ih8mud.com/80-series-tech/538233-water-temp-sensor.html

https://forum.ih8mud.com/80-series-tech/554667-p0125-o2-sensor-ect-sensor.html

 

[Olaf]

The fan clutch is blue hub from toyota. The ect is not oem.

The ect sensor seems to be a good place to look next and will be easy to replace with oem sensor. Will also check for air in system.

The links for this code are helpful. I changed my non oem o2 sensors out for densos in january, got the correct wiring from denso and no more of those codes. One way or another been struggling with this code since then.

 

[Olaf]

Put in Toyota ect sensor, cleared codes and after fifty miles p0125 came back. Only two things left I can think of are radiator and water pump. Any insights would be great.

'97lx, 290,000 arb, mate blk, emu lift, engine rebuilt, etc...

 

[cary]

Put in Toyota ect sensor, cleared codes and after fifty miles p0125 came back. Only two things left I can think of are radiator and water pump. Any insights would be great.

'97lx, 290,000 arb, mate blk, emu lift, engine rebuilt, etc...

I don't think either. It is saying that it isn't sensing a warm enough temperature fast enough. You are not overheating and your radiator is relatively new so I would move that down the list of possibilities. Water pumps rarely go bad, and if it did, you should seek overheating pretty fast (i.e. impeller disintegrated).

I would focus on two areas:

1) Cooling System- Possible thermostat stuck open. I would replace with a new OEM thermostat and carefully re-bleed the system.

2) Electrical- I think this is more likely. I bet if you were to trace the coolant sensor wire, you would find a bad connection or break in the wire. The easiest way to check would be to find where the wire enters the computer or close to it, prick it with a needle and use an electrical tester to test for continuity from the connector to where you prick the wire. Move the cable around in case there is an internal break that is leading to an intermittent connection.

 

[Olaf]

I think you're right. Got ride of codes from o2 sensors last winter. Will check the wiring on the ect sensor. Need to learn how to use an ohm meter? Wiring is not what I'm best at.

New sensor and the factory temp gauge is reading below half most of the time.

What's the down side to living with this code? Getting twelve mpg around town.

'97lx, 290,000 arb, mate blk, emu lift, engine rebuilt, etc...

 

[cary]

I believe with this code you are never going closed loop, which can result in a lean or rich condition and shorten cat life.

 

[Olaf]

With the new Toyota ect sensor factory temp gage looks better. Got reader for on board computer. Temp almost never goes over 185.

Replaced upstream o2 sensor, with denso. Got ride of code p0125, runs closed loop intermittently getting new code p0135 any help or ideas. Think I'm closing in on getting this all resolved.

'97lx, 290,000 arb, mate blk, emu lift, engine rebuilt, etc...

 

[Olaf]

Made some progress on these issues.

Truck doesn't want to run closed loop. Now getting the p0130, p0133, and p0135 TC's. Front O2 sensor reading .2 and rear reading .9 at highway speeds with tstat around 180. Struggling with this for a while. Changed fan clutch to blue hub, ect sensor, new radiator, new front o2 in november, back o2 2years old, tstat factory. Getting 11 to 12 mpg combined.

Got rid of other codes. Can't get to run closed loop consistently.

Rear o2 sensor may be the issue, LTFT often 19. Any help would be great.

'97lx, 290,000 arb, mate blk, emu lift, engine rebuilt, etc...

 

[Mbridenour]

I replaced my upstream o2 with a Bosch and got the same codes, ohmed out the heater and it only ohmed 3.4, took it back and the next one ohmed the same..FSM says they should be 11-16. Got a factory o2 it checked out at 13.4 and no more codes.

 

[Olaf]

I replaced my upstream o2 with a Bosch and got the same codes, ohmed out the heater and it only ohmed 3.4, took it back and the next one ohmed the same..FSM says they should be 11-16. Got a factory o2 it checked out at 13.4 and no more codes.

Replaced upstream censor with denso in November, that helped. Still have these codes. Ordered downstream denso o2 sensor today. Hope that's the fix. Thanks

'97lx, 290,000 arb, mate blk, emu lift, engine rebuilt, etc...

 

[Olaf]

Over the last two weeks replaced downstream o2 sensor, EGR modulator and hoses, still getting codes. P0130, p0133, p0135 and p0401. Getting consistent readings from related sensors. The problem seems to be with the STFT, it. When it's 0 loose closed loop and and throw codes.

There was a lot of carbon in the hose coming out of the EGR, but replaced. Any guidance. Car is running well, but mileage is off a little.

'97lx, 290,000 arb, mate blk, emu lift, engine rebuilt, etc...

 

[Olaf]

Over the weekend replaced EGR valve. STFT is between 0 and 19.53, LTFT has gone to 0 and stayed there. Front o2 reads around .3 , rear o2 reads .02 to .9, still getting p0135.

Just about out of ideas. Anyone?

'97lx, 290,000 arb, mate blk, emu lift, engine rebuilt, etc...

 

[Sweetwally]

ECU Short

I was informed that I had a short on my ECU due to sloppy mechanical work when they replaced my rear valve cover gasket. (left off a ground wire to throttle body)

I have replaced just about as much as you and still this P0125.

Mine comes on when I get the RPM's above 2K. I can drive the car for hours at slow speeds and the light stays off. I almost think I have an exhaust leak also?


1997 Avalon (84,000 miles)

 

[Olaf]

sorry to hear about you p0125.

I soldered the wiring on my O2 sensors and the p0125 is gone.

Now I'm getting p0130 p0133 p0135 p0141 and pending p0171. Getting .3 on front O2 and .9 on back running 2200 rpms. stft 19.53 and ltft 19.53.

Thinking it's the wiring combinations on the o2 sensor. No harnesses so hard wired and soldered. Called denso and got different info than a lexus mechanic. Did trial and error to get where it's at.

Would love it if someone could tell me the corresponding colors for the o2's front and back.

 

[Olaf]

Found someone with same year LC, crawled underneath and looked at the o2 wires. Is as follows: front sensor T LBW - D L, T G - D B, T Yr - D B, T BRB - D W; rear sensor T L - D L, T O - D B, T YR - D B, T BRB - D W. reconnected the the wires, soldered, will have to see.

'97lx, 290,000 arb, mate blk, emu lift, engine rebuilt, etc...