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2001 Toyota Highlander transmission issue

I have a 2001 Toyota Highlander, V6. I had two O2 sensors replaced in August. I now have an issue with the transmission. In normal in town traffic, after I come to a stop for the third time at a stop light and start moving again, the transmission will not go into the highest gear and the RPM’s go to 3000 to 4000 at 55 mph. If I shut the car off and restart it, I can go another three stops before the problem occurs. My mechanic has cleaned the mass air flow sensor and it temporarily corrects the problem. But then it returns. Restartng the car leads me to believe the the issue is electrical sensor related but cleaning the mass air flow sensor seems to work temporarily too. Are the two somehow related is this something that is easily diagnosable but somehow missed by my mechanic (he is an independent shop)?

The two are probably related and its likely that your mechanic should be doing better.

If you really want to know go to a transmission specialty shop rather than a general mechanic - but NOT to a national chain transmission shop. You want a local, owner-operated place. They can put it on a scanner and find out what it is doing and why.

Has your mechanic actually put it on any kind of scanner - to, for example, read what the MAF sensor is doing? Has your check engine light been on?

When you say that cleaning the MAF “temporarily” corrects what counts as temporary? 100 miles? 1000? Do you have a specialty air filter such as a K&N?

Thanks. Great advice. My mechanic has done me well in the past but may not be the transmission diagnostics shop that I need. I’ll take it to a local transmission shop for diagnosis. The check engine light has been on which is what prompted the O2 sensor work. After repair, the light went off for about a week then returned with this transmission issue. His mechanic in the shop has noted the MAF and cleaned it and the problem stopped for about a week, then returned. So “temporarily” would be about 300 miles. I’ll check the air filter too.

Can you get the codes for us?
You can take it to an Auto Zone, pep Boys, or some other car parts place, and they typically do it for free.

Give us that info, and we might be able to help you pin point the issue a bit better.


The code is P0330. He said that it came up as a knock sensor. Could it somehow be related to a transmission issue?

If your car is misfiring you naturally press down further on the gas to try to maintain speed.This causes the transmission to downshift to a lower gear and since your car doesn’t have enough power to go faster it won’t up-shift. I thought I had a transmission problem when I took a route that included a steep hill I had had no trouble with before,but now my car would not take the hill in high gear. All I needed was new plugs.

How about the air filter question? Do you have OEM or some something like the K&N filters?

Sorry for the long delay, here is an update on the transmission issue. Thanks to all who replied and your patience as I come and go on business trips, sidetracking my quest to get this quickly resolved. I visited a local transmission shop as suggested and after 2 hours of testing it they could not explain why it would not shift into upper gear intermittently. They noted the knock sensor for the check engine light but did not come up with any codes for transmission issues. They also recommended that I replace the timing belt so I had them replace it and the water pump at the same time. Gear issue not resolved. So I contacted the local Toyota dealership and explained over the phone the issue. He had never heard of such a thing and would need to see the car first. He said it sounded like an electronic issue since turning off the engine cleared the problem temporarily. To answer some previous replies, the engine does not misfire. Outside of the engine not going into the top gear, it runs very well and I would not know that there was even a problem. This makes it even more puzzling. I went ahead and bought a K&N filter and I now get better gas mileage but still have the issue with the higher gear. Recently, I spoke to the father of a friend who was a mechanic and he immediately said that it was the idle speed sensor, an electronic part. It would at least make partial sense to me in that it is electronic and does give me some hope. Any thoughts on the idle speed sensor? Does that make any sense to anyone?

I have the same car with the same issue. The big name trans shop was ready to pull out the trans but that did not sit well with me. I was wondering if there was a drainage issue in the trans and was about to change the screen. Before I tried that I decided it must be the knock sensor. I check my own codes and that one keeps coming up. I was going to ignore it because my car runs so well until the trans won’t up shift. Have you replaced the knock sensor yet and did it solve your problem or did you discover any other solution.

I haven’t replaced the knock sensor yet, but my knock sensor code shows up also. My issue started in the summer with the replacement of (2) O2 sensors. The upshifting issue started shortly after those were replaced. It was suggested to me by a retired mechanic that it was an idle speed sensor. I haven’t been able to find a lot of information on idle speed sensors, it’s probably called something else and I don’t know where to start to locate information on it. It’s nice to know that I am not the only one with this issue. If anyone else has any suggestions before either of us starts sinking money into our trans, please let us know.

Did anything ever come of your situation? Did you ever find out the cause? I currently have a 2001 Highlander that will not upshift at about 45 mph. The Knock sensor code is registering as the check engine light is on.
One mechanic suggested the TPS (throttle position sensor) might be the problem.
It goes in the shop in a few days to be evaluated.

I am having the same issue with my 2001 Toyota Highlander. I have replaced the knock sensors and wire harness. The issue is still there. Has anyone else fixed the issue? If so, how?

@dyt_ryan … suggest to post your problem as a separate thread here, you’ll get better, more informed, replies than tacking onto this thread. Click “maintenance/repairs” link at the top of this page, then you’ll see “ask a question” box or something like that on the upper right. Seems possible there could be involvement between knock sensor problems and the transmission function, as the engine computer is trying to preserve the health of the engine by decreasing the amount of knocking until the problem is resolved. Knocking can damage an engine, and severe knocking can damage an engine quickly. The computer might limit some transmission functions to prevent that.

Did you get ur highlander looked at?

Please start your on thread. This one is confusing enough.

I had the knock sensor replaced along with the wire harness. Seems to be running like new so far.