P0125 CEL won’t clear

Hello, I have a 1999 tacoma 2.7L 5 speed 4wd and I have had a P0125 CEL for what seems like forever. I have replaced everything that has to do with the Coolant system such as the thermostat, ect sensor and the plug. Can anyone help me to get to the bottom of this?

 

Id want to look at the live data and see what the computer is reading from the ect sensor and if it makes any sense.

 

Reference the attached PDF. Your potential trouble areas are:

 

The P0125 has nothing to do with coolant temp like the name would suggest, it sets when the ECM doesn't see a response from the O2 sensor after the vehicle has been driven for more than 2 minutes.

I'd want to look at O2 sensor data and see what it's reading, if it's stuck at 0v need to check the O2 sensor and circuits.

 

I read the description of operation and I found something interesting... on the top of DI-46 there is a "HINT", confirm voltage data from CURRENT DATA. Correct me if I am wrong but I am interpreting this as use OBDII generic live data as opposed to manufacturer specific (year, make, model). Thoughts?

 

Generally if your looking at an OEM flow chart if they say to look at data they are referring to the OEM side.

In this case OEM or Global OBDII data would net the same results.
The main advantage of using Global OBDII data would be that it must use standard SAE terms and also manufacturers are forbidden from displaying substituted values in Global mode.
The disadvantage to Global OBDII data is generally a much slower refresh rate and a very limited number of available data PIDs.

 

understood...

the reason that I mentioned it is that I chased substituted values on a MAF on a Ford truck a while back, I just could not understand why I was getting acceptable g/sec air flow when the truck ran like crap, sometimes. After a phone call and an explanation I changed to Global OBDII data and saw that the g/sec were a quasi flat flat line with spikes. I wasted over an hour going down that rabbit hole. It turned out to be a small spider had crawled up into the sampling tube and died and his body with curled up legs would rise and fall in the tube giving weird readings. I made the call on the MAF and I figured I am going to replace it anyway, let me take a look and see whats going on, I figured I cant break it anymore, that's when I discovered the spider.

you always remember the ones that kick your ass.

 

I've ran into debris in the MAF sensor multiple times on Fords, first one kicked my butt for a little bit but I figured it out pretty quick.

Yea substituted values can really send you on a goose chase, I've had incorrect/invalid scan data screw with me too before. This is why one ideally should have multiple scan tools of different brands if in the business of diagnosing vehicles.

 

Great, that makes me feel better that I am not the only one "lucky" enough to have experienced these things.

 

I have an 01 Tacoma and I have noticed corrosion of the male and female pins in the ECU main connectors. ((I had some random codes and a check engine light that was persistent)) ((BE SHURE TO DISCONNECT THE GROUND OFFF YOUR BATTERY BEFORE DOING ANY ecu WORK OR WELDING ON YOUR FRAME))ECU pins are gold plated, but mine corroded anyway. I found a purple spray called ACF 50 which is what the military uses to clean corroded electrical pins and parts. I removed the glove box and carefully pulled all the connectors open. (you may want to label them first?) and sprayed the pins and sockets down good with the ACF 50. Then you want to CAREFULLY engage and disconnect the harnesses several times to dislodge any crusty stuff that may still be sticking to any of the pins. Then hook up everything again and check your codes again.
The ACF 50 can be left in the connector wet and it does not short anything out, so no need to dry it out again. Miracle stuff for any electrical connectors!