Part 1
ENGINE CONTROL COMPONENTSAccelerator Pedal Position (APP) Sensor
The APP sensor is an input to the powertrain control module (PCM) and is used to determine the torque demand. There are 3 pedal position signals in the sensor. Signal 1, APPS1, has a negative slope (increasing angle, decreasing voltage). Signals 2 and 3, APPS2 and APPS3, both have a positive slope (increasing angle, increasing voltage). During normal operation APPS1 is used as the indication of pedal position by the strategy. The 3 pedal position signals make sure the PCM receives a correct input even if a signal has a concern. There are 2 reference voltage circuits and 2 signal return circuits for the sensor.
Air Conditioning (A/C) Clutch Relay
The A/C clutch relay (may be referred to as the wide open throttle (WOT) A/C cutoff relay) is wired normally open. There is no direct electrical connection between the A/C switch or electronic automatic temperature control (EATC) module and the A/C clutch. The PCM receives a signal indicating that A/C is requested. When A/C is requested, the PCM checks other A/C related inputs that are available. If these inputs indicate A/C operation is OK, and the engine conditions are OK (coolant temperature, engine RPM, throttle position), the PCM grounds the wide open throttle A/C cut-off (WAC) output, closing the relay contacts and sending voltage to the A/C clutch.
Air Conditioning Evaporator Temperature Sensor (ACET)
The ACET is connected to the dual automatic temperature control (DATC). Evaporator temperature is transmitted to the PCM from the DATC through the controller area network (CAN) for freeze control protection.
Air Conditioning (A/C) High Pressure Switch
The A/C high pressure switch is used for additional A/C system pressure control. For refrigerant containment control, the normally closed high pressure contacts open at a predetermined A/C pressure. This results in the A/C turning off, preventing the A/C pressure from rising to a level that would open the A/C high pressure relief valve.
For fan control, the normally open medium pressure contacts close at a predetermined A/C pressure. This grounds the ACPSW circuit input to the PCM. The PCM then turns on the high speed fan to help reduce the pressure.
For additional information, refer to Heating and Air Conditioning, Climate Control.
Air Conditioning (A/C) Low Pressure Switch
The A/C low pressure switch is used for additional A/C system pressure control. This normally closed switch opens when the refrigerant pressure drops below 152 kPa (22 psi). This results in the A/C turning off, preventing the evaporator from freezing.
Air Conditioning (A/C) Refrigerant Distribution Valve (ACRDV)
Air Conditioning (A/C) Refrigerant Distribution Valve (ACRDV):
The ACRDV is a PCM controlled solenoid that provides a regulated control of refrigerant flow to the passenger compartment loop. The PCM opens or closes the ACRDV based on the passenger compartment A/C request. The ACRDV is a normally closed valve, preventing the refrigerant flow. When the passenger compartment A/C is requested ON, the PCM provides a ground path to the solenoid which opens the ACRDV.
Battery Power Off (BPO) Request
The traction battery control module (TBCM) checks the inertia fuel shut off switches, the high voltage interlock (HVIL) circuit, and the traction battery lid tamper switch for an open circuit condition. If the open circuit condition is not detected, the TBCM continuously toggles the BPO output, typically generating a 2 Hz pulse width modulated signal to the PCM. The TBCM also broadcasts a normal message to the PCM over the communication link. When the TBCM detects a condition, it changes the pulse width modulated signal frequency to 6 Hz at 50% duty cycle and broadcasts an error message to the PCM over the communication link. The error message and the 6 Hz frequency indicate to the PCM that the traction battery opens the contactors in 1 second. After the contactors are open the PCM carries out a normal power down sequence to the transaxle control module (TCM) and DC/DC converter.
Brake Pedal Position (BPP) Switch
The BPP switch is a normally open switch that, when closed, sends a signal to the PCM when the brake pedal is applied. The PCM strategy uses this signal input to aid the PCM in determining the correct function and operation of the vehicle speed control, the electronic throttle control (ETC), and the transaxle and regenerative braking systems. The BPP switch is hard wired to the PCM and supplies positive battery voltage (+12 volts) when the brake pedal is applied. When the brake pedal is released, the BPP switch opens and no battery voltage input is sent to the PCM.
Brake Pedal Switch (BPS)
The BPS used for vehicle speed control deactivation is a normally closed switch, which supplies positive battery voltage (+12 volts) to the PCM when the brake pedal is released. When the brake pedal is applied, the normally closed switch opens and power is removed from the BPS circuit to the PCM.
The normally closed BPS, along with the normally open BPP switch, is used by the PCM strategy for a brake pedal rationality test. The PCM strategy looks for each switch to change states when the brake pedal is applied and released. If a failure occurs in one or both of the brake pedal inputs a diagnostic trouble code (DTC) P1572 is set and the PCM misfire on board diagnostic (OBD) monitor is disabled.
Camshaft Position (CMP) Sensor
Camshaft Position (CMP) Sensor:
The CMP sensor is a variable reluctance sensor that detects the position of the camshaft. The CMP sensor identifies when piston number 1 is on its compression stroke. A signal is then sent to the PCM and used for synchronizing the firing of sequential fuel injectors. The PCM also uses the CMP signal to select the proper ignition coil to fire. The input circuit to the PCM is referred to as the CMP input or circuit.
Canister Vent (CV) Solenoid
Canister Vent (CV) Solenoid:
During the evaporative emissions (EVAP) leak check monitor, the CV solenoid seals the EVAP canister from the atmospheric pressure. This allows the EVAP canister purge valve to obtain the target vacuum in the fuel tank during the EVAP leak check monitor.
Clean Tachometer Output (CTO)
The PCM uses a crankshaft position (CKP) sensor input to calculate the engine speed. The engine speed information is then output to the transaxle control module (TCM) through the CTO circuit, as a frequency signal. The PCM also broadcasts a redundant engine speed message to the TCM over the controller area network (CAN) communication link. When the broadcasted engine speed disagrees with the hardwired CTO signal, or when the CTO circuit concern condition is detected, the TCM stores an appropriate diagnostic trouble code (DTC).
Coil On Plug (COP)
Coil On Plug:
The COPs are part of the distributorless ignition system. They are the source of the high voltage which is used to generate the spark by the spark plug. The hybrid vehicle uses 4 COPs, one for each cylinder. The COPs are mounted directly onto the spark plugs. The function of the COP is to convert low voltage into high voltage in excess of 40,000 volts.
The COP consists of primary and secondary windings. the primary winding is energized by the IGN START/RUN circuit. The PCM coil driver circuit is connected to the primary winding as well. The secondary winding is connected to the spark plug. The current flowing through the primary winding generates the magnetic field across both windings. The PCM activates the coil driver circuit by opening it. The instant the circuit opens the magnetic field collapses, inducing current flow in the secondary winding.
The COP has 3 different modes of operation: engine crank, engine running, and CMP failure mode effects management (FMEM).
Crankshaft Position (CKP) Sensor
Crankshaft Position (CKP) Sensor:
The CKP sensor is a magnetic transducer mounted on the engine block adjacent to a pulse wheel located on the crankshaft. By monitoring the crankshaft mounted pulse wheel, the CKP is the primary sensor for ignition information to the PCM. The pulse wheel has a total of 35 teeth spaced 10 degrees apart with one empty space for a missing tooth. By monitoring the pulse wheel, the CKP sensor signal indicates the crankshaft position and speed information to the PCM. By monitoring the missing tooth, the CKP sensor is also able to identify piston travel in order to synchronize the ignition system and provide a way of tracking the angular position of the crankshaft relative to a fixed reference. The PCM also uses the CKP signal to determine if a misfire has occurred by measuring rapid decelerations between pulse wheel teeth.
Cylinder Head Temperature (CHT) Sensor
Cylinder Head Temperature (CHT) Sensor:
The CHT sensor is a thermistor device in which the resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases, and the resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.
Thermistor type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow.
The CHT sensor is installed in the aluminum cylinder head and measures the metal temperature. The CHT sensor can provide complete engine temperature information and can be used to infer coolant temperature. If the CHT sensor conveys an overheating condition to the PCM, the PCM then initiates a fail-safe cooling strategy based on information from the CHT sensor. 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. Using both the CHT sensor and fail-safe cooling strategy, the PCM prevents damage by allowing air cooling of the engine and limp home capability.
DC/DC Enable (DCE)
The DCE is an output from the PCM to the DC/DC converter. The PCM enables the DC/DC converter after the PCM receives a contactors closed message and no error messages. The DCE circuit is high (the low side driver is off) when the DC/DC is commanded on. When the DCE low side driver is activated,the DC/DC converter is commanded off.
DC/DC Fault
The DC/DC fault (DCF) signal is an input to the PCM from the DC/DC converter. This signal is low under normal conditions and switches high when a concern exists within the DC/DC converter cooling system, the high voltage power supply to the DC/DC converter, or the low voltage output system. The PCM disables or limits the operation of the DC/DC converter by the DC/DC enable circuit (DCE), when a DCF concern is indicated.
Electronic Throttle Body (ETB) Position Sensor
The ETB position sensor has 2 signal circuits in the sensor for redundancy. The redundant ETB position signals are required for increased monitoring. The first ETB position sensor signal (TP1) has a negative slope (increasing angle, decreasing voltage) and the second signal (TP2) has a positive slope (increasing angle, increasing voltage). During normal operation the negative slope ETB position sensor signal (TP1) is used by the control strategy as the indication of throttle position. The 2 ETB position sensor signals make sure the PCM receives a correct input even if a signal has a concern. There is 1 reference voltage circuit and 1 signal return circuit for the sensor.
Evaporative Emission (EVAP) Canister Purge Valve
EVAP Canister Purge Valve:
NOTE: The EVAP canister purge valve may also be referred to as a vapor management valve (VMV).
The EVAP canister purge valve is part of the enhanced EVAP system that is controlled by the PCM. This valve controls the flow of vapors (purging) from the EVAP canister to the intake manifold during various engine operating modes. The EVAP canister purge valve is a normally closed valve. The electronic EVAP canister purge valve controls the flow of vapors electronically by way of a solenoid, thereby eliminating the need for an electronic vacuum regulator and vacuum diaphragm. The PCM outputs a variable duty cycle signal (between 0% and 100%) and a variable current (between 0 mA and 1000 mA) to the solenoid on the EVAP canister purge valve.
Exhaust Gas Recirculation (EGR) System
For information on the electric EGR system, refer to Exhaust Gas Recirculation (EGR) System.