Hard Shifting - No Overdrive

[JasonG]

My 1999 RX300 has been shifting very hard and will not go into overdrive. I had a CIL code that said the knock sensor was bad. After reading through this forum, I concluded that the knock sensor was causing the hard shifting and preventing the trans from shifting into overdrive.

I ordered the sensors, new sensor wire, and gaskets; had them replaced and still have the problem.

It shifted fine for about three miles. Then it started shifting hard again.

The trans was replaced two months ago, when a trans shop said the trans was bad. So now I have a new trans, new sensors, new sensor wire, the CIL is now off, there are no codes, and I still have the problem.

Can I get some ideas please?, I'm stumped!

Jason.

[wwest]

My 1999 RX300 has been shifting very hard and will not go into overdrive. I had a CIL code that said the knock sensor was bad. After reading through this forum, I concluded that the knock sensor was causing the hard shifting and preventing the trans from shifting into overdrive.

I ordered the sensors, new sensor wire, and gaskets; had them replaced and still have the problem.

It shifted fine for about three miles. Then it started shifting hard again.

The trans was replaced two months ago, when a trans shop said the trans was bad. So now I have a new trans, new sensors, new sensor wire, the CIL is now off, there are no codes, and I still have the problem.

Can I get some ideas please?, I'm stumped!

Jason.

You may need to find a way to "match" the new transaxle with the "proper" engine/transaxle ECU control firmware version appropreate to your Vin #.

For instance the transaxle the third party shop installed in your RX may be from an entirely different model year.

[mehullica]

When the knock sensors were replaced, was the ground harness by the pcv hose and behing the intake bolted back on? The one behing the intake near the engine removal hook is easy to leave unbolted and will cause hard shifting from the trans. The one by the pcv hose should be 2 wires held on by a 12mm nut on the side of the intake. The one behind the intake is a 2 wire held on by a 1omm bolt. Check these first.

[JasonG]

When the knock sensors were replaced, was the ground harness by the pcv hose and behing the intake bolted back on? The one behing the intake near the engine removal hook is easy to leave unbolted and will cause hard shifting from the trans. The one by the pcv hose should be 2 wires held on by a 12mm nut on the side of the intake. The one behind the intake is a 2 wire held on by a 1omm bolt. Check these first.

I'll check that. Also, it is now shifting into over drive. It shifts smoothly from 1st to 2nd, but 2nd to 3rd is hard.

The guy that replaced tha trans did some work to it after it was replaced and before the knock sensors were replaced. I wonder if he now needs to undo whatever he did to try and fix the hard shifting, (which we didn't know was the knock sensor at that time)?

[mehullica]

After the trans is replaced, the engine ecu must be reset using a scantool. Disconnecting the batttery will not erase the learned shift values completely, even if you unhook the battery for a week, it will not reset completely. A scan tool must be used to actually reset the values to begin relearning the new trans clearance and shift characteristics. Conservative driving habits with premium fuel will relearn within 400 miles. Regular fuel will take longer and actually increase the time delay between each upshift due to lack of the engine ecu's capability to use it's full range of ignition advance from the cheap gas. I know this for a fact as I've replaced at least 90 of these transaxles.

[JasonG]

After the trans is replaced, the engine ecu must be reset using a scantool. Disconnecting the batttery will not erase the learned shift values completely, even if you unhook the battery for a week, it will not reset completely. A scan tool must be used to actually reset the values to begin relearning the new trans clearance and shift characteristics. Conservative driving habits with premium fuel will relearn within 400 miles. Regular fuel will take longer and actually increase the time delay between each upshift due to lack of the engine ecu's capability to use it's full range of ignition advance from the cheap gas. I know this for a fact as I've replaced at least 90 of these transaxles.

Can the Autozone scan tool do this reset?

[mehullica]

No, you'll need a scantool that is high end. Toyota/Lexus, OTC, Snap-On types will have a reset function that only resets the trans side of the engine/trans ecu. A generic code reader/clearer won't do the job. Most dealers will reset it for you if that all you need done. It takes about 1-2 minutes.