So I apologize in advance for making this my first post but I'm pretty stumped on this one. I recently bought a 96 LS400 and while taking it to pass emissions it is showing all of the non-continous monitors as "not ready". Thinking it was just not set since the car had been sitting I drove it the last week, about 600 miles total and still nothing. I have checked all of the fuses and everything seems fine, no codes either. I'm thinking ECU but I wanted to check here first. Thanks for the help guys, hopefully it's nothing too serious.

 

is your ECT properly working? what's the ECT reading?

 

did you look for PENDING codes and not just active codes?

 

ECT is working properly between normal and power. I have only been driving with it on normal though.

I did not. I'm only use a generic auto parts store style scanner. What kind of scanner would I need to look for pending codes?

Thanks guys.

 

a higher level OBDII scanner should do the trick, you shouldn't need a dealership quality scanner lol.

 

ok, I'll see if I can get it checked out tomorrow. Anything else I should look for given no pending codes?

 

So no pending codes either. Any ideas?

 

ECT as in your temperature sensor. What is your ECT reading at normal operating temperature? Find someone with a scanner that is capable of reading Live Data. If your ECT is not at the correct temperature, it will affect ALL Monitors to "Not Complete". Open thermostat, low coolant or air in system is a possibility also.

 

Are you saying the readiness test are not done yet? That basically means someone erase and reset your computer prior to you buying it. It was either to cover up a code that popped up or they just repaired something.

Fill tank up, start from cold, do a casual drive, try to keep speed below 60 and try to maintain 30-45 miles per hour as long as possible. 50 miles should do the trick..

 

readiness should be ready unless the car has been recently been reset with battery disconnected (maybe to erase cel code?)
you need to drive about 50 miles to have the ECU ready for smog.

 

This makes a lot of sense. Didn't know the cooling system could have that effect so that will be the first thing I look at. Thanks a lot.

Yeah the readiness monitors are not setting. The car had been sitting for a while before I bought so I assumed the battery died or something and the monitors reset. I've driven it 500+ miles since and did the drive patterns and not one has set.

 

check the battery grounds and make sure that the wiring and fuses are all correct.

you could try hunting for a '96 ECU but i'm not a fan of blindly throwing parts at a problem.

 

It was just the coolant temp sensor. 7 ready now and I only drove it 10 miles. Thanks do much guys, you saved me a lot of money.

 

Learning something new everyday.

 

Ok, so apparently that didn't fix the issue completely but it was definitely part of the problem. Now the monitors are setting as I drive but it seems the ecu is resetting every time I turn the car off. I made a video to show you guys, don't mind the radio in the background.