Vehicle applicability: This diagnostic supplement covers multiple Ford vehicles and engines. Follow the application named in the source below. Some references apply to vehicles other than Mustang.
1-12 Description and Operation
Engine Control Components
Typical AAT Sensor
Barometric Pressure (BARO) Sensor
The BARO sensor measures barometric pressure to estimate the exhaust back pressure.
For direct injection vehicles, a BARO sensor is mounted internally to the PCM. The BARO sensor measures the barometric pressure to estimate the exhaust back pressure.
For vehicles without a BARO sensor and with a MAP sensor, the BARO value is inferred by the PCM based on the MAP value under certain operating conditions. At, or near wide open throttle the BARO value is calculated to be slightly higher than the MAP value, with the difference calculated by the pressure drop across the throttle plate.
For all other vehicles without a BARO sensor, the BARO value is inferred by the PCM based on the volumetric efficiency of the engine, comparing the mass air flow (MAF) sensor and the ambient temperature values. The actual MAF value is used to calculate an inferred MAP value based on operating conditions and volumetric efficiency. At, or near wide open throttle, the BARO value is calculated to be slightly higher than the inferred MAP value, with the difference calculated by the pressure drop across the throttle plate.
Brake Pedal Position (BPP) Switch
The BPP switch is sometimes referred to as the stoplamp switch. The BPP switch provides a signal to the PCM indicating the brakes are applied. The BPP switch is normally open and mounted on the brake pedal support. The BPP switch supplies battery positive (B+) voltage to the PCM when the brake pedal is applied.
Typical BPP Switch
Brake Pressure Switch
The brake pressure switch is used for cruise control deactivation. The brake pressure switch is a normally closed switch and is typically mounted on the brake pedal support. When the brake pedal is applied, the normally closed switch opens.
On some applications the normally closed brake pressure switch, along with the normally open BPP switch, are used for a brake rationality test within the PCM. The PCM misfire monitor profile learn function may be disabled if a brake switch concern occurs. If one or both brake pedal inputs to the PCM is not changing states as expected, a DTC is set by the PCM strategy.
2016 Powertrain Control/Emissions Diagnosis, Gasoline Engines, 3/2015
2016 Mustang workshop publication supplied to Mustang Atlas. Original technical text and illustrations; HTML formatting by Mustang Atlas. Source page numbering is retained for traceability. Follow the configuration, revision, warnings, and cross-references in the material. About this edition.