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.
Description and Operation 1-53
Powertrain Control Software
The fail-safe cooling strategy is only activated by the PCM when an overheating condition has been identified. This strategy provides engine temperature control when the cylinder head temperature exceeds certain limits. The cylinder head temperature is measured by the CHT sensor. For additional information about the CHT sensor, refer to Engine Control Components in this section.
A cooling system failure, such as low coolant or coolant loss, could cause an overheating condition. As a result, damage to major engine components could occur. Along with a CHT sensor, the fail-safe cooling strategy is used to prevent damage by allowing air cooling of the engine. This strategy allows the vehicle to be driven safely for a short time with some loss of performance when an overheat condition exists.
Engine temperature is controlled by alternating the number of disabled fuel injectors, allowing all cylinders to cool. When the fuel injectors are disabled, the respective cylinders work as air pumps, and this air is used to cool the cylinders. The more fuel injectors that are disabled, the cooler the engine runs, but the engine has less power.
A wide open throttle (WOT) delay is incorporated if the cylinder head temperature is exceeded during WOT operation. At WOT, the injectors function for a limited amount of time allowing the customer to complete a passing maneuver.
Before injectors are disabled, the fail-safe cooling strategy alerts the customer to a cooling system problem by moving the IPC temperature gauge to the H (hot) zone and setting DTC P1285. Depending on the vehicle, other indicators such as an audible chime or warning lamp, can be used to alert the customer of fail-safe cooling. If overheating continues, the strategy begins to disable the fuel injectors, DTC P1299 is stored in the PCM memory, and a malfunction indicator lamp (MIL) illuminates. If the overheating condition continues and a critical temperature is reached, all fuel injectors are turned OFF and the engine is disabled.
Failure Mode Effects Management (FMEM)
The FMEM is an alternate system strategy in the PCM designed to maintain engine operation if one or more sensor inputs fail.
When a sensor input is determined to be out of limits by the PCM, an alternative strategy is initiated. The PCM substitutes a fixed value for the incorrect input and continues to monitor the suspect sensor input. If the suspect sensor begins to operate within limits, the PCM returns to the normal engine operational strategy.
Flash Electrically Erasable Programmable Read Only Memory (EEPROM)
The flash EEPROM is an integrated circuit within the PCM. This integrated circuit contains the software code required by the PCM to control the powertrain. One feature of the EEPROM is that it can be electrically erased and then reprogrammed through the data link connector (DLC) without removing the PCM from the vehicle.
Flex Fuel
Flex fuel vehicles are designed to be compatible with any combination of ethanol and gasoline up to 85% ethanol (E85). The percentage of ethanol content in the fuel is inferred by the PCM flex fuel strategy.
The fuel level input (FLI) determines if a refueling event has occurred after an ignition ON or while the engine is running. If a refueling event is detected, the PCM saves the current inferred ethanol value. The PCM flex fuel strategy recognizes a refueling event as gasoline or E85, and enables the flex fuel learn procedure. The flex fuel strategy will infer the correct air to fuel ratio, based on the oxygen sensor input, to maintain stoichiometry after the vehicle refueling event occurs.
The new fuel is calculated to reach the engine after a calibrated amount of fuel has been consumed from the fuel lines and fuel rails. Normal long term fuel trim learning and EVAP purge control are temporarily disabled to allow the new ethanol content to gasoline percentage to be inferred. Ethanol content learning continues until the inference is stabilized within the engine operating conditions.
Typical flex fuel vehicle operation:
• The initial air to fuel ratio and flex fuel percentage is calculated for gasoline after a keep alive memory (KAM) reset. Vehicles that have
E85 in the fuel tank after having a KAM reset may result in a hard start when cold, or a cold engine acceleration lack of power, until the PCM flex fuel strategy calculates the correct percentage of ethanol content in the fuel.
• A cold start with alcohol blended fuel may be more difficult than with gasoline, due to the lower volatility of alcohol blended fuel.
• Ethanol requires more fuel flow than gasoline, and flex fuel vehicles require a higher flow injector.
• Vehicles with flex fuel capability have the fuel type identified on the fuel filler pipe.
Fuel Level Input (FLI)
The FLI is a communications network message. Most vehicle applications use a potentiometer type FLI sensor connected to a float in the fuel pump (FP) assembly to determine fuel level.
Fuel Trim
Short Term Fuel Trim
If the oxygen sensors are warmed up and the PCM determines the engine can operate near the 14.7 to 1 (9 to 1 E100) stoichiometric air to fuel ratio, the PCM enters closed loop fuel control mode. Since an oxygen sensor can only indicate rich or lean, the fuel control 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.