2002 Lexus Shifting and Noise Concerns

A 2002 Lexus RX300 equipped with a 3.0-liter V6 engine and U140F transmission was brought into our facility with a few concerns. The customer stated, "It has a leak, a grinding noise when taking off from a stop, and it just doesn't seem to shift right." They went on to tell us that this noise had been intermittently occurring for about a year, there were no warning lamps on, and they also stated they make frequent stops. It was also revealed that the vehicle had been to other shops to address these concerns with no success. A different shop had replaced both front axles, but that did not correct their issue, so they took it to another shop after they lost confidence from the initial shop's attempt at repair.

The second shop they went to recommended that the transmission should be replaced with no real explanation as to why, so at this point, they had asked friends for advice on whom to trust with their vehicle and one of them was a previous customer of ours, and therefore referred him to our location.

After the customer interview, we performed our evaluation of the vehicle. This includes a scan of the vehicle's control systems and collecting DTCs stored in any of the vehicle modules, a battery and charging system test, a road test of the vehicle to duplicate the customer's concern, and then performing an under-hood/under-vehicle inspection. On a previous 2002 RX300 I had been fooled by a bad ground on the back of the intake manifold before, and although there is a fairly specific concern associated with that ground issue, I always look at it first on these cars just to make sure. The ground was intact on this car.

The results of my evaluation revealed no DTCs stored in any of the modules. After several consecutive stops, I was able to duplicate the customer's concern about a grinding sound when just starting to accelerate from a stop. The transmission was not shifting well; it had kind of a slide-bump on the 1-2 shift and a flare on the 2-3 shift and I also noticed a "judder" feel on take-off at the same time the noise was heard. During the under-vehicle inspection, I saw that there was a leak between the transmission and the PTU, and also from the output seal on the PTU. The transmission fluid condition was poor and the PTU fluid was low, thick, and black in color.

This vehicle had about 180k on the odometer. In my opinion, it had too many miles to warrant any attempt at any kind of repair on the existing transmission, so I determined the transmission along with the PTU needed to be replaced. The customer was advised on what we had found and what the options were for repair, and the customer then authorized the repairs. He was a little reluctant due to the cost, but he was out looking at and pricing used cars before he came in and knew what he was looking at to replace it. To add, for this application, Certified Transmission includes a remanufactured PTU with the reman transmission, so they basically come as a set.

The transmission and PTU were replaced. There is a specific ECM memory reset that needs to be done:

Reset Procedure 2002 RX300

1. Connect the Toyota Diagnostic Tester to the vehicle.
2. Reset the ECM (PCM).
3. Start the engine and warm it up to normal operating temperatures before test-driving.
4. Perform a thorough test drive with several accelerations from a stop with "light throttle" application until proper transmission shifting is verified.

After the reset procedure was performed, we performed a final road test to make sure the vehicle was working properly, leak-free, and ready to return to the customer. During the final road test, the transmission was shifting very nicely but noticed that the grinding and judder feel were still present. There were no codes and not much information to lead us in the right direction. There was no indication of an issue with the scan tool PIDs.

We began researching possible causes. A TSB containing information about noise and vibration was found: SU007-02.

Armed with this information, we drove the vehicle again while monitoring the wheel speed sensors. What we found was at low speed (under 3 mph), the right rear wheel speed sensor was dropping out and reading 0 mph causing activation of the traction control and causing a noise and vibration feel. (Figure 2)

We inspected the right rear wheel speed sensor. We found that the connector was secure and that there were no visible cuts or breaks in the wiring. We removed the speed sensor and did a visual inspection and found that the magnet was covered in metal particles. (Figure 3)

We opted to replace the speed sensor and drove the vehicle again. We took another movie of the speed sensors, and all the readings were correct. There was no more errant traction control activation. (Figure 4)

Even though the TSB addressed the same noise we were experiencing, we did not have to do everything indicated in the TSB. What the TSB did for us was lead us in a direction that would eventually identify our problem area. The vehicle is now shifting correctly, there are no leaks, and the noise has been eradicated.

The vehicle was driven a couple more times to confirm everything was working correctly. After doing so, the vehicle was then returned to a very pleased customer.