Last post on Nov 29, 2013 at 10:06 PM
You are in the Toyota Highlander
What is this discussion about?
Toyota Highlander, Transmission, SUV
#167 of 314 2003 Highlander - Jerking Transmission in low gears
Oct 08, 2009 (7:47 am)
I recently had my engine replaced in my 2003 HL and within 10 miles, the lower gears would start "jerking." It is fine when engine is cold (which isn't long). Tranny fluid replaced. Toyota service (not where I had work done) says that I should drive the car for awhile (months) to "reprogram the transmission to my driving patterns." What kind of "driving patterns" have to be programmed for a car to "learn" how to go from 1st gear to 4th gear? Any thoughts?
#168 of 314 Re: 2003 Highlander - Jerking Transmission in low gears [fixrixsix]
Oct 08, 2009 (8:43 am)
Your driving habits, in this instance, have NOTHING to do with the engine/transaxle ECU's "learning" process.
But the newly restored engine POWER/TORQUE might.
So Toyota might be correct.
OUCH, that HURT...!!
#169 of 314 Re: Transmission Trouble? [paul143]
Oct 11, 2009 (8:01 am)
I have the exact same problem. I have had my highlander for 3 days and just noticed it. Did you ever find out what the cause was and the fix?
#170 of 314 Re: Transmission Trouble? [casandraw]
Oct 12, 2009 (5:03 pm)
OK, what is the deal. Just purchased an 09 Highlander Sport AWD and noticed the same issue as both of you. Noticeable shutter when the accelerating uphill and the car shifts into 5th. Then the shuttering starts. I did notice it when we bought the car but thought it was the road. After several test runs I am convinced there is an issue. The Toyota dealer of course said we have not heard of any issues.
Have you come up with anything???
#171 of 314 Re: Transmission Trouble? [minnesnowta1]
Oct 12, 2009 (8:07 pm)
Since they made a significant design change in their transaxle design back late in the last century that resulting in several unforeseen problems (poor thought process), Toyota has been struggling to come up with a FINAL solution. One of the fixes they tried very early on resulted in localized overheating of the ATF.
It appears that as a result they have been overly cautious about the issue of more closely controlling ATF line pressure, ALL aspects of line pressure. The goal seems to be constantly keeping the line pressure as low as seeming possibly in order to reduce the ATF heating due to pressurization to the n'th degree.
So I find it not surprising that some of you are getting clutch "chatter", shuttering, once you reach roadspeeds that dictate the use of higher gears ratios. Higher gear ratios reduce the need for high line pressure so my guess would that Toyota, yet again, is cutting things just a tad too close.
That makes it all the harder for me to understand just why the solution Ford took for solving the exact same problem in the Edge transaxle design was not acceptable to Toyota.
#172 of 314 Re: Transmission Trouble? [casandraw]
Oct 13, 2009 (7:18 am)
I have it with the transmission folks now. I will let you know what happens. Seems to have to do with the fluid pressure and they may have to replace a part. More later.
#173 of 314 Re: Transmission Trouble? [fixrixsix]
Oct 13, 2009 (9:20 am)
They might replace one of the pressure controlling solenoids which may solve your problem until the engine/transaxle ECU completes the (re)learning process for the new solenoid and then begins to optimize FE again.
The engine/transaxle controlling ECU must get a "mind-wipe", go back to the factory default, rolling off the production line, parametric mapping, any time a new component of this class is installed.
It might be wise, worthwhile, to know which solenoid they replace that you can later do a mod, provide a biasing current, should the condition return.
#174 of 314 Re: Transmission Trouble? [wwest]
Oct 14, 2009 (6:02 am)
What you are saying makes a lot of sense. When I addressed the issue with Toyota service mgr at the dealer I bought my Highlander from he said it may have to do with the learning curve of the computer for the transmission. It has like the adaptive learning control that adjust the transmission to your style of driving. He said to put on at least a 600 to 1000 miles on the vehicle before being concerned. Might be BS but I will wait a while and see if it corrects itself. This problem started from day 1 of the purchase so we will see.
#175 of 314 Re: Transmission Trouble? [minnesnowta1]
Oct 14, 2009 (10:26 am)
The electronic control system of most modern day automatic transmissions make use of several 12 volt electric solenoids. Most of these operate in simple servo "bang-bang" mode, on/off, plunger either fully relaxed (spring return) of fully deployed.
But there are 1 or 2 functions that require "linear" displacement of the solenoid actuator plunger, line pressure control for instance. Eons ago it was considered that a simple electric solenoid could not be used in this manner. Then along came the idea, ability, to modulate the plunger position "linearly" via the use of PWM, Pulse Width Modulation, voltage duty cycle control of how far the actuator was to be deployed.
The next problem was, what was to be used as feedback to the controlling device to denote the actuators control position...?? A new off-the-shelf solenoid could be roughly "calibrated" insofar as voltage applied vs actuator movement/position and while that might be close enough for the factory default control mapping parameters it was not satisfactory for the fine position tuning control required once installed within the vehicle.
The answer was...The function being controlled. Clutch slip within the transaxle...?? Increase the line pressure via a slight increase in PWM voltage. You didn't need to calibrate the solenoid to exacting actuator position, that could be done "on-the-fly" as the vehicle is driven.
I believe the first use of this technique for automobile engine control was to control the idle air bypass valve. Two feedback sensors are used to do this, the upstream oxygen sensor an an engine RPM, timing sensor. The solenoid must be adjusted to the point of allowing just the right amount of air through the bypass port that the idle air/fuel mixture is correct in accordance with the upstream oxygen sensor(s) and the RPM remains at a steady 800RPM.
Disconnect the battery and the IAV control will default to the factory parametric PWM settings, but after a fairly brief period of time the ECU will have learned, pretty much exactly, what level of voltage is required to hold the solenoid in the correct "linear" position to satisfy the feedback parameters. Now it will go to that "setting" each and every time you start the engine.
Plug up the bypass port slightly with debris, oil wicked into the intake path from a K&N followed by dirt, the ECU will simply re-learn, again and again, over an over again, the level of PWM voltage to be used to "meter" the proper airflow.
Plug up the bypass port too much and the solenoid will not have enough range, you get a CEL. Clean the bypass port and over a period of time the ECU will have learned the new parameters. Disconnect the battery and that period of time will shorten.
#176 of 314 Re: Transmission Trouble? [minnesnowta1]
Oct 14, 2009 (10:44 am)
"..adjust the transmission to your style of driving..."
What your service manager doesn't understand, "get", is that there are two categories of ECU learning/relearning. Yes, the engine/transaxle ECU will "watch" how fast you "normally" depress the gas pedal AND how fast you "normally" release it. The time it takes you to move your foot from the gas pedal to the brake is even important insofar as adapting to a specific driver's driving style.
But parameters of/in that category MUST be erased for each an every stop/start engine cycle.
But there are MANY other engine/transaxle control parameters that must be learned and/or continually relearned as you drive. Let's say the knock/ping sensor "sounds off" during acceleration (excluding engine lugging with a stick shift and/or ignition timing too early). The ECU must quickly adjust, enrich, the A/F mixture via EFI to abate the knock/ping. But now the engine will be operating below the factory design "standard" and the ECU will periodically run A/F mixture leaning, optimization trials, in case the engine is now being "fed" with the proper, premium, fuel.