Powertrain Control Module (PCM) Inputs

POWERTRAIN CONTROL MODULE (PCM) INPUTS

Accelerator Pedal Position (APP) Sensor
For information on the APP sensor, refer to Torque Based Electronic Throttle Control (ETC). Description and Operation

Air Conditioning Cycling Switch (ACCS) Circuit
The ACCS circuit to the powertrain control module (PCM) provides a voltage signal which indicates when A/C is requested. When the A/C function selector switch is turned on, voltage is supplied to the ACCS circuit at the PCM. Refer to Vehicle/Diagrams for vehicle wiring.

If the ACCS signal is not received by the PCM, the PCM does not allow the A/C to operate.

Air Conditioning Evaporative Temperature (ACET) Sensor

ACET Sensor Voltage And Resistance:

The ACET sensor monitors the evaporator air discharge temperature. The ACET sensor is a thermistor device in which resistance changes with temperature. The ACET sensor is used to more accurately control A/C clutch cycling, improve defrost/demist performance and reduce A/C clutch cycling. The electrical resistance of a thermistor decreases as the temperature increases, and the resistance increases as the temperature decreases. The PCM sources a low current 5 volts on the ACET circuit. With SIG RTN also connected to the ACET sensor, the varying resistance affects the voltage drop across the sensor terminals. As the A/C evaporator air temperature changes, the varying resistance of the ACET sensor changes the voltage the PCM detects.

Air Conditioning (A/C) Full Demand Switch
The A/C full demand switch circuit provides a voltage signal to the PCM which indicates the MAX A/C, DEFROST, or FLOOR/DEFROST mode is requested. If the engine is shut down during normal engine operation the PCM restarts it when A/C full demand is selected. The engine will remain running when the A/C full demand switch is selected allowing the A/C compressor to circulate the refrigerant for the passenger compartment.

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.

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) Recirculation Switch
The A/C recirculation switch circuit provides a voltage signal to the PCM which indicates the A/C recirculation mode is requested. The PCM requests the traction battery cooling system to enter the recirculation mode when the PCM receives the A/C recirculation signal.

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 fault condition. If the open circuit fault condition is not detected, the TBCM continuously toggles the BPO output, typically generating a 2 Hz pulse width modulated signal to the powertrain control module (PCM). The TBCM also broadcasts a normal message to the PCM over the communication link. When the TBCM detects a fault 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 DTC P1572 is set and the PCM misfire 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.

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. For additional information, refer to Powertrain Control Software Fail-Safe Cooling Strategy. Powertrain Control Software

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 fault 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 fault is indicated. For additional information on DCF, refer to the DC/DC converter description in Hybrid Electric Control Hardware. Description and Operation

Electronic Throttle Position (TP) Sensor
For information on the electronic TP sensor, refer to the description of the Torque Based Electronic Throttle Control (ETC). Description and Operation

Fuel Pump Monitor (FPM)

Fuel Pump Driver Module (FPDM) Duty Cycle Signals:

The fuel pump driver module (FPDM) communicates diagnostic information to the PCM through the FPM circuit. This information is sent by the FPDM as a duty cycle signal. The 3 duty cycle signals that may be sent are listed in the table.

Fuel Tank Pressure (FTP) Sensor
For information on the FTP sensor, refer to the description of the Evaporative Emission (EVAP) System.

Fuel Rail Pressure Temperature (FRPT) Sensor

Fuel Rail Pressure Temperature (FRPT) Sensor:

The FRPT sensor measures the pressure and temperature of the fuel in the fuel rail and sends these signals to the PCM. The sensor uses the intake manifold vacuum as a reference to sense the pressure difference between the fuel rail and the intake manifold. A fuel return line to the fuel tank is not used in this type of fuel system. The relationship between fuel pressure and fuel temperature is used to determine the possible presence of fuel vapor in the fuel rail. Both pressure and temperature signals are used to control the speed of the fuel pump. The speed of the fuel pump maintains fuel rail pressure by keeping fuel in its liquid state. The dynamic range of the fuel injectors increases because of the higher rail pressure, which allows the injector pulse width to decrease.

Heated Oxygen Sensor (HO2S)

Typical Heated Oxygen Sensor (HO2S):

The HO2S detects the presence of oxygen in the exhaust and produces a variable voltage according to the amount of oxygen detected. A high concentration of oxygen (lean air/fuel ratio) in the exhaust produces a voltage signal less than 0.4 volt. A low concentration of oxygen (rich air/fuel ratio) produces a voltage signal greater than 0.6 volt. The HO2S provides feedback to the PCM indicating air/fuel ratio in order to achieve a near stoichiometric air/fuel ratio of 14.7:1 during closed loop engine operation. The HO2S generates a voltage between 0.0 and 1.1 volts.

Embedded with the sensing element is the HO2S heater. The heating element heats the sensor to temperatures of 800°C (1,400°F). At approximately 300°C (600°F) the engine can enter closed loop operation. The VPWR circuit supplies voltage to the heater and the PCM turns on the heater by providing the ground when the proper conditions occur. The heater allows the engine to enter closed loop operation sooner. The use of this heater requires that the HO2S heater control be duty cycled to prevent damage to the heater.

Ignition Switch Position Run (ISP-R)
The ISP-R provides the PCM with a VBAT input signal from the ignition switch, indicating that the key is either in the ON or START position. When the operator turns the key to the OFF or ACC position, the internal combustion engine immediately ceases to provide power. The PCM coordinates the power down sequence by controlling the power sustain circuit and issuing the proper commands to shut down the electrical system in an orderly fashion, refer to the Normal Power Down Sequence in Hybrid Electric Control Software. The PCM maintains power to the transaxle control module (TCM) through the power sustain circuit until the power down sequence is complete. The traction battery control module (TBCM) is always powered directly from the low voltage battery which permits wake-up when the vehicle is off.

Ignition Switch Position Run/Start (ISP-RS)
The ISP-RS provides the PCM with a VBAT input signal from the ignition switch, indicating the key is in the START position.

Intake Air Temperature (IAT) Sensor

Integrated Intake Air Temperature (IAT) Sensor:

The IAT sensor is integrated into the mass air flow (MAF) sensor. It is a thermistor device in which 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.

A thermistor-type sensor is considered a passive sensor. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in the total current flow.

Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.

The IAT provides air temperature information to the PCM. The PCM uses the air temperature information as a correction factor in the calculation of fuel, and ignition timing.

Knock Sensor (KS)
The KS is a tuned accelerometer on the engine which converts engine vibration to an electrical signal. The PCM uses this signal to determine the presence of engine knock and to retard spark timing.

Manifold Absolute Pressure (MAP) Sensor

Manifold Absolute Pressure (MAP) Sensor:

The MAP sensor uses a piezo-resistive silicon sensing element to provide a voltage proportional to the absolute pressure in the intake manifold.

The MAP sensor is part of the exhaust gas recirculation (EGR) system. The PCM uses information from the MAP sensor, throttle position (TP) sensor, mass air flow (MAF) sensor, cylinder head temperature (CHT) sensor and crankshaft position (CKP) sensor to determine how much exhaust gas is introduced into the intake manifold.

Mass Air Flow (MAF) Sensor

Mass Air Flow (MAF) Sensor:

The MAF sensor uses a hot wire sensing element to measure the amount of air entering the engine. Air passing over the hot wire causes it to cool. This hot wire is maintained at 200°C (392°F) above the ambient temperature as measured by a constant cold wire. If the hot wire electronic sensing element must be replaced, then the entire assembly must be replaced. Replacing only the element may change the air flow calibration.

The current required to maintain the temperature of the hot wire is proportional to the volume of air flow. The MAF sensor then outputs an analog voltage signal to the PCM proportional to the intake air mass. The PCM calculates the required fuel injector pulse width in order to provide the desired air/fuel ratio.

The MAF sensor is located between the air cleaner and the throttle body inside the air cleaner assembly.

Motor Electronics Coolant Temperature (MECT) Sensor

Motor Electronics Coolant Temperature (MECT) Sensor:

The MECT sensor is a thermistor device in which 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. A thermistor-type sensor is considered a passive sensor. 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. Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor. The MECT provides motor electronics coolant system temperature information to the PCM. The PCM uses this information for determining when to activate the cooling system fans and indicate over-temperature.

Restraint Deployment Indicator (RDI)
The RDI is an input signal sent from the restraints control module (RCM) to the PCM indicating an air bag deployment. The signal is a zero to VPWR 50% duty cycle, that is .83 Hz for a normal condition, and 5 Hz indicates a deployment event has occurred. Refer to Air Bag Systems.

Speed Control Switch
For information on the speed control switch, refer to Cruise Control.

Torque Of Generator-AC (TGAC) Signal
The transaxle control module (TCM) calculates an AC generator torque from an AC current measured by the current sensor which is located inside the transaxle. The TGAC is a 50% duty cycle signal which the TCM sends to the PCM over the TGAC circuit. The TCM also broadcasts a redundant generator torque message to the PCM over the communication link. The typical TGAC signal ranges from 200 Hz to 400 Hz, where 300 Hz is equal to 0 Nm (0 lb ft) of torque, 200 Hz is equal to 250 Nm (185 lb ft) of negative torque, and 400 Hz is equal to 250 Nm (185 lb ft) of positive torque. The PCM uses the generator torque value as an input to the energy management control strategy, the torque monitor strategy, and the regenerative brake torque limits strategy. In the event of TGAC circuit failure the PCM initiates limited operating strategy (LOS) shutdown mode which disables the vehicle. The PCM also stores an appropriate DTC.

Torque Of Motor-AC (TMAC) Signal
The transaxle control module (TCM) calculates an AC traction motor torque from an AC current measured by the current sensor which is located inside the transaxle. The TMAC is a 50% duty cycle signal which the TCM sends to the PCM using the TMAC circuit. TCM also broadcasts a redundant traction motor torque message to the PCM over the communication link. The typical TMAC signal ranges from 200 Hz to 400 Hz, where 300 Hz is equal to 0 Nm (0 lb ft) of torque, 200 Hz is equal to 250 Nm (185 lb ft) of negative torque, and 400 Hz is equal to 250 Nm (185 lb ft) of positive torque. Positive torque is perceived as vehicle acceleration and negative torque is perceived as braking. The PCM uses the traction motor torque value as an input to the energy management control strategy, the torque monitor strategy, and the regenerative brake torque limits strategy. In the event of TMAC circuit failure the PCM initiates limited operating strategy (LOS) shutdown mode which disables the vehicle. The PCM also stores an appropriate DTC.

Transmission Range (TR) Sensor - Analog

Gear Selector Assembly:

Transmission Range (TR) Sensor - Analog:

Voltage Versus Angle And Gear Selected Chart:

Overview
The TR sensor communicates the gear selector position that the driver selects to the PCM. The PCM determines a gear mode based on the TR input and the vehicle speed signal. The PCM then broadcasts a gear mode message over the communication link. The transmission control module (TCM) uses the gear mode message to engage the transaxle in the gear that the driver selected. The other control modules use the gear mode message to control the rear lamps or a brake shift interlock solenoid. The TR sensor is mounted at the base of the gear selector assembly and the sensor shaft is moved by the selector.

TR Sensor and PCM Interface
The TR sensor is a linear potentiometer device that provides the PCM with a percentage of input voltage proportional to the rotational angle of the sensor shaft. The TR sensor consists of:
- 3 independent (TR-A1, TR-A2 and TR-A3) signals.
- 2 5 volt reference (TR-VREF1 and TR-VREF2) lines.
- 2 signal return (TR-RTN1 and TR-RTN2) lines.

The TR-A1 signal has a negative voltage slope, meaning the voltage decreases when the sensor angle increases. The typical TR voltage ranges from approximately 4.5 volts in the PARK position to approximately 1 volt in the LOW gear position. The TR-A2 and the TR-A3 signals both have a positive voltage slope. Voltages increase as the sensor angle increases. The typical voltage for the TR-A2 and the TR-A3 range from about 0.6 volts in the PARK position to about 3.5 volts in the LOW gear position.

The TR-VREF circuits are bussed together internal to the TR sensor, and both TR-RTN circuits are bussed together in the TR sensor. One of the TR-VREF and one of the TR-RTN circuits are dedicated signals from the PCM. This design of redundant signals protects against an open circuit condition.

If the PCM detects a fault condition in one of TR signal inputs, it uses the other 2 TR signals to determine what gear the driver selects. If the PCM detects 2 or more TR signals that are invalid, the PCM:
- allows the vehicle to travel in DRIVE position or LOW gear position if the vehicle was driving forward at a significant speed when the fault was detected.
- allows the vehicle to travel in REVERSE gear if the vehicle was driving backwards at a significant speed when the fault was detected.
- broadcasts gear mode - NEUTRAL over the communication link when vehicle speed decreases to 8 km/h (5 mph).
- sets the diagnostic trouble code (DTC) and illuminates the indicator light.