I am having the same problem with the computer (ECM) not resetting on my 2000 Toyotoa Tundra. I have not changed the battery, but it has not passed the NH state inspection emissions test for the last 2 months. I have also had it retested about 5 or more times. Likewise, I took the truck to a local Toyota Dealership. They ran a comprehensive diagnosis of the ECM, but it showed no problems. And I have had no check engine light or error codes from the sensors for the last year. A year ago, I had to replace 2 x O2 sensors, but have had no check engine light since then. Incidentally, my 2000 Tundra is being recalled due to rust on the frame, which is very extensive. So I took it to a better Toyota dealership, and they evaluated the rust and advised me that the catalytic converter was also shot & needs to be replaced. I have called Toyota Customer Service hoping they will buy back the Tundra. Could this problem with the Cat. Converter (or other severly rusted exhaust components) be causing the problem with the ECM not resetting without giving any error codes/check engine light?
Which of the Monitors have not passed? There should be four or five depending on whats installed on your vehicle. There is o2 sensor, o2 heater, Cat monitor evap monitor and egr monitor.
The ECM (computer) won’t reset eventhough NONE of the sensors/monitors show an error code. We do not have a check engine light either. We have been retesting the ECM every two weeks for the last two months, but the ECM doesn’t reset itself – ie. ALL of the emissions monitors report that they are “Not ready for testing.” The Toyota dealership tested the ECM and it passed their diagnostic tests.
I’m not familiar with toyota scan tools, but they may be able to check the starts since cleared counter. If the counter is very low or 0 then the ecm is resetting, but not in the way you want it to. Basically it’s acting like the battery has been disconnected even though it hasn’t been. Have the battery tested, or depending how long it’s been installed replace it. Then drive the car on the highway through a full warm up period. This should reset all but your evap monitor which should run overnight (as long as the fuel tank is 1/4 to 3/4 full). I have seen this same problem with mopar batteries resetting the CARB monitors and not showing any signs of low charge.
On the innova scan tool, a monitor won’t show a code; it will flash if it is not in ready status. You have to get the scanner, sold at Wal-Mart for about $98. When the experts fail, you have to be your own expert. THEY can’t fix the problem by saying catalytic converter and walking away.
If we didn’t have scanners, and the car were an 85, I would say to disconnect the battery for a minute and reconnect. If the car were a 1985, I would buy a reconditioned computer for $100. They cost a LOT more now.