ecm issues.

Goodmorning everyone, hope everyone had a good thanksgiving. I am new to the forum and working on cars. I am mechanically inclined but by no means a professional. Some some background information on my car. It all started with me failing emissions because the cat monitor o2 monitor 02 heater monitor or not ready. I was instructed to drive the car for a certain number of days and come back when it was ready but they never were ready, I did some research and unpluged one of the o2 sensors to apply a voltmeter, to check continuity, voltage etc. Upon doing so I forgot to plug it back in and started the car. I was surprised that I never got a obd pending code, out of curiosity I unplugged the iac and still no codes, I unplugged an ignition coil and the car misfired and still no codes/CEL finally I unplugged the map sensor and the car sputtered and died. But still no hard set code, pending codes, or check engine light. According to the readings I get from live data this truck is happy as a clam. So I suspected that the reason the monitors won't set us the computer can isn't receiving and logistic readings? I still don't know what could cause the monitors to set but the not setting any codes or CEL should be an esm issue right?

 

Codes are often set after 'x' key starts that the fault is seen. Eliminates random events that way.

 

FIRST, get yourself an OBD2 scan tool that will display live data ( it will have a larger display than just code reader ) reconnect everything and start and run the vehicle.

does check engine light illuminate on "key on" ? it should illuminate on start up and then go out ( if everything is good ) if it doesn't light there may be other issues.

all of the mentioned sensors will have displayed values on the scan tool. one thing to check is coolant temp. if engine does NOT reach operating temp, it will stay in "open loop" and several of the sensors won't operate correctly. if after several minutes the engine hasn't reached 190° sitting and idling, pretty good chance the thermostat is stuck open (common failure) and the monitors will not run to check sensors.

 

O2 sensors won't start working until they reach a certain temp either

 

make sure your CEL isn't burnt out

 

Thanks for the responses guys. the check engine light does come on when the key is in the on position and after starting it does go out. I have a snap on solus ultra and can see the live data. I show an engine temperature of 186 degrees after 15 min of idle. I have benched tested the thermostat with a heat gun and can see the thermostat open, but i changed it anyways since it was so cheap. While looking at live data i can see values for everything and they change as i rev the engine, put load on it etc. but no pending codes. What really cooks my noodle is when i unplug something like an ignition coil the misfire counter stays at zero. There are no reported misfires in any of the cylinders, unplug IAC and the live data freezes but there is still no code thrown, unplug on of the oxygen sensors, the data freezes but no open sensor heater circuit code is thrown. Before throwing another ECM at the problem i would like to cover my bases and properly diagnose this. thanks any ideas or suggestions are welcome and appreciated. thanks fellow tacomaers!

 

would the monitors not run if the ECT was reporting at 186 degrees instead of 190?

 

how far have you driven the truck since problem occurred ? Some vehicles have to be driven several warm up (drive) cycles (186 isn't really warm enough)

that O2 heater open isn't detected is kind of curious, but it may also need a few key cycles to set

take it out, drive it like you stole it, monitor engine temps in doing so. if you're using aftermarket T-stat, it could still be the issue, I've had my share of bad ones, consecutively. monitors won't trip if engine doesn't reach operating temp.
Heating with heat gun only tells you it opens, you have no idea what temp it was opening. opening too early it may as well be stuck open, as it won't close when needed ( you'd be surprised how often the T-stat cycles open and closed, especially when temps are below freezing)

 

Good morning everyone, thought I'd post this before going to work. So as to this time I have driven the truck 105 miles, hard. I noticed that the lower radiator hose is cold no matter what. I changed the thermostat again. But the hose is still cold, when I stop the radiator fan from turning the lower radiator hose then starts to warm up and the temperature in live data goes up as well. I did put a new radiator in this thing not too long ago. Monitors are still not setting, I'm stuck. Lol feel like setting her on fire. Joking*

 

Make sure the spring part is in the engine block not upside down. Also you might have air inside the block, if you can raise the front of the truck to get any air out of the engine. https://www.youtube.com/watch?v=PGkSfPbGr3Y

 

Thanks for the video, so I remember putting in the thermostat the same way I took it out. I had the good fortune of replacing the thermostat for the 3rd time, when I filled it back up I turned on the heat in the cabin and used a filler radiator funnel tool thing. Big yellow lots of adaptors for different radiators. I also lifted up the car from the front about 2 feet, temperature still idles at 186 when I step on it it increases to 187.

 

Monitors Still Not ready. Any ideas?

 

Sounds like it's doing it's job, at basically 180 degrees. Their are some set at 180, 192, and 212 Fahrenheit . What is it stamped on the thermostat housing? Some are stamped in Celsius which it's about 83, which would make it about 182. Then you have to a tolerance of +/- accuracy of your instrument, along with the +/- accuracy of the thermostat. Your well with the acceptable accuracy range.

 

your temperature needs to be at ~210f/100c before it will work properly. figure that out first. Or drive 10 miles and see if your temperature raises to boiling point

 

I looked on line at a new standard temperature thermostat for 2000 V6, they're 180 degrees. Look at the one you pulled out, to see what their stamped. Agree with undyingvisage58 you need to drive it, don't remove the cap cause it'll be under pressure when it reaches full temperature.

 

Have you Checked ALL the fuses ? If the ECM loses power when key of it reset and monitors have to retest

 

Yes I have checked the fuses to make sure the ecm is getting power. What I don't understand is how the car runs and drives, but I cannot get a check engine light to save my life. Nothing I do, unplug or even try to mess up will throw a check engine light. But there are no drivability issues. I have plenty of power the car doesn't run rough or stall, I can see live data.

 

Everything leads me back to the ecm.

 

Cant be the ecm, cause the only problem im seeing is that you cant drive the truck for long enough to warm up the engine. It needs to get to 210f/100c before it will start those final tests. or sit in your driveway and dont idle it. Keep it around 2krpm until it reaches 210/100

 

I believe that the computer should be logging fault codes for the disconnected sensors regardless of temp. It may not go into closed loop until the O2 sensors reach proper temp, but I think (key word) it should still log fault codes if the MAF, TPS, IAC, etc. are disconnected with the engine running.