BA Falcon accelerator pedal position (APP) failure … are you sure?
Vehicle starts, runs up to 1500rpm and shuts down.
Scan tool displayed the following codes:
- P0121 Throttle position sensor – circuit range /performance
- P2110 Throttle actuator control system (TAC) – forced limited rpm
(in this instance complete shutdown)
- P2127 Throttle/Pedal position sensor (switch E) – low input
- P2129 Throttle/Pedal position sensor (switch E) intermittent input
- P2132 Throttle/Pedal position sensor (switch F) low input
- P2134 Throttle/Pedal position sensor (switch F) intermittent input
- P2135 Throttle/Pedal position sensor A and 8 voltage correlation fault
- P2138 Throttle/Pedal position sensor D and E voltage correlation fault
- P2139 Throttle/Pedal position sensor D and F voltage correlation fault
- From the code set, we can see issues with the TPS/APP, and low/intermittent voltage input (reference voltage to sensors) on sensors E and F, and APP sensor correlation issues
Looking at the circuit in questions, the APP is a combination of three individual sensors, with two wired with common reference and return wiring, with the third a separate sensor although still within the primary unit.
When mechanical control is taken away from the driver, in this case the removal of the throttle cable (fly by wire) electronic redundancies must be employed, to provide safety (run away situation). If a single APP sensor fails, the ETC light illuminates. It takes the failure of two APP sensors to initiate limp mode/part throttle.
This particular vehicle was checked and found to have only 2V on the 828 connection supplying both sensors one and two.
It was discovered that the power steering switch (PSS) which normally is closed at rest, and provides 5V to pin 833 from 831.
When power steer ing pressure increases (when turning) this circuit opens. The faulty PSS allowed partial current return causing a corruption and in turn caused the 5-volt reference to be corrupted.