# Handling Intermittent Problems



## bwilson4web (Mar 4, 2019)

As a former Prius owner we faced charges at Toyota of "Unintended Acceleration" in the 2008-2010 time frame. This led to a lot of technical investigation helped in part because the Toyota schematics were in the repair manuals. In one case, a college instructor connected a decade box (set of resistors) to the accelerator wires and with a reporter driving the car, flipped a switch and the car took off without an error code:





Now the professor modified the Toyota wiring to induce two faults: (1) connecting two accelerator pedal inputs together, and; (2) setting a resistance that signaled full throttle. He converted a duplex system into a mono system and then set a fault . . . echos of the Boeing 737 MAX flipping between two angle of attack sensors which allowed one failed sensor to fly the airplane into the ground . . . twice. Without the schematics and a test part, I can't tell if something like this is possible in our Model 3.

In the Toyota "Unintended Acceleration" case, the National Highway Traffic and Safety Administration (NHTSA) opened up an investigation and a lot of skilled investigators reported their findings including NASA. Toyota went with Hall effect sensors replacing the dual-pots and other manufacturers revealed techniques for detecting a wiring problem. One of the best was using different rates between the two accelerator position so a "short" could be detected. With parallel resistance rates, tying the two sensors together can not be detected. Add a second fault, a fixed resistance, and the car acts as if the accelerator was floored. So what data has NHTSA collected about our Model 3:
2018 TESLA MODEL 3 4 DR RWD

Scroll down and you'll see 57 complaints of which there were significant numbers of "Unintended Acceleration:"

Date ID type
05/22/19 11209238 acceleration
05/15/19 11207877 acceleration
05/07/19 11206155 acceleration
04/22/19 11202909 acceleration
04/16/19 11196764 acceleration
11/30/18 11164094 acceleration
11/26/18 11154132 acceleration
10/03/18 11133222 acceleration
09/28/18 11132177 acceleration
09/01/18 11124067 acceleration
08/02/18 11119991 acceleration
07/27/18 11115496 acceleration
05/22/18 11097159 acceleration
05/10/18 11092830 acceleration
05/04/18 11091970 acceleration

*HYPOTHESIS*

These intermittent failures suggests there may be one or more, random problems. For example, my cell phone failed to work as a key yesterday. So I cleared the problem by:

Power reset iPhone
Brake reset Model 3
Unfortunately, I was in a hurry and did them in parallel so I can't identify a specific fault. A second example was when I lost Traffic Aware Cruise Control (TACC), I recovered it by doing:

Display reset while driving
Intermittent problems seldom occur in isolation. Resolving one can leave a second one that has to be identified and fixed. So we can't rule out a random, accelerator circuit problem. Absent analysis of the Model 3 schematics, there _may be_ a fault mode that can lead to unintended acceleration.

Recommended Follow-up

Document the problem - file both with the NHTSA and Tesla. It makes sense to first file with NHTSA and then cite the incident number in an e-mail via your Tesla Account email. Include any corrective actions and whether or not they worked.
Serial attempts to clear - do one change at a time and see if it clears the problem: (1) iPhone power cycle if involved; (2) Display reset, and; (2) Brake reset. There is a "Power" option in the display software that may be included.
Bob Wilson


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