2010 Mazda CX9 Electronic Throttle Control Circuit Identification

John Diagnostician California Posted  
2010 Mazda CX-9 Grand Touring 3.7L (MZI) 6-spd
P0122 — Throttle/Pedal Position Sensor/Switch "A" Circuit Low

The wiring diagrams that we had access to only showed the throttle body as a "box" with 6 wires connecting to it. Hopefully this will help others with circuit identification and functions of this Electronic Throttle Control system(ETC). This vehicle came to us from another shop with a P0122 code. The throttle body had been replaced 3 times. The last time with a new unit from Mazda. This ETC system is like many others. An electric motor moves the throttle plate to the desired angle as determined by the PCM. Throttle position is reported back to the PCM by 2 throttle position sensors integral to the throttle body. TPS 1 outputs about 4.3v at closed throttle. The voltage decreases as the throttle is opened. TPS 2 outputs about 0.5v at closed throttle. The voltage increases as the throttle is opened. We found that the TPS1 signal wire was shorting to ground on the transmission .We have attached a wiring diagram on which we have labeled the circuits at the throttle body. Before and after repair scan data and scope captures of all 6 circuits are attached. TPS1 shorting to ground caused the PCM to interpret the 0v reading as 100% throttle opening. We hope this helps someone. Thanks for your time.