Engine Stop/Start (Ess) Inhibitors
The following conditions must be true for the vehicle to perform an ESS auto stop event:
- An ABS event not present
- Flex fuel learned is true
- ESS related system faults are not present
- Driver seat belt buckled
- Driver door closed
- Driver Presence Detection Module (DPDM) indicates seat is occupied
- If the vehicle is equipped with an ATX, any forward transmission gear state must be detected
- If the vehicle is equipped with a MTX, the transmission must be in neutral with the clutch pedal in a released state
- ESS inhibit START/STOP Off switch is not pressed
- Battery state is at an acceptable level
- ECT is within calibrated range
- Ambient temperature is within calibrated range
- Steering wheel inputs are acceptable
- Engine speed is below a calibrated threshold
- Vehicle speed is below a calibrated threshold (APPS indicates that the throttle pedal is not pressed)
- Vehicle latch speed achieved (ESS auto-stop is permitted)
- Starter motor engagement frequency has not exceeded the calibrated number of allowable attempts
- Brake booster vacuum level is within calibrated range
- Barometric pressure value is within calibrated range
- Hood not open and no rationality faults present
- Hill grade is below calibrated range and HSA is ready
- Fuel level is within calibrated range
- Master cylinder pressure in allowable range to perform auto-stop and HSA
- Engine run time is above a calibrated threshold
- Transfer case status is in acceptable state (not in 4-Low). Reported by the Drivetrain Control Module (DTCM).
- Park maneuver is not detected
- Transmission is ready for ESS operation
- No faults present in the ATX or MTX transmission
- HVAC demand is not present
- Oil temperature is within a calibrated range
- Variable Valve Timing (VVT) is in default position
- Exhaust Gas Recirculation (EGR) is ready (if equipped)
- Multi-air system ready (if equipped)
- Starter diagnostics are not running
- Catalyst light is off
The following conditions allow for engine start:
- No OBDII compliant faults are present or detected
- Hood ajar switches are indicating a closed state.
- No ESS inhibit or ESS disarm conditions are present.
- Starter strategies managed by the PCM indicate that starter operation is allowable.
- RPM readings are below a run threshold calibrated by the PCM.
Certain ESS related system faults and vehicle conditions will inhibit the ESS operation. The following items on this list can be listed due to rationality faults, sensor faults, hardware faults, communication faults or SNA faults:
- Ambient temperature during engine restart
- Catalyst temperature during engine restart
- ECT during engine restart
- Battery temperature during engine restart
- Engine oil temperature during engine restart
- Certain HVAC load demands
- Cam sensor faults; intermittent or otherwise
- Cam/crank rationality; intermittent or otherwise
- Accelerator Pedal Position Sensor (APPS) faults detected
- Steering Angle Sensor (SAS) faults during engine restart
- Driver door ajar switch fault
- Seat belt circuit fault
- Hood detection fault
- Clutch pedal position faults
- Hill Start Assist (HSA) within range to hold the vehicle faults
- Brake booster pressure faults
- Fuel level faults during engine restart
- Torque security faults
- Loss of bus communication during engine restart
- Accelerometer sensor diagnostics
- Starter control. Anything that disables first crank would disable ESS
- Starter relay fault
- Starter relay circuit faults
- Air bag deployment
- Driver Presence Detection Module (DPDM) faults
- PCR Stuck Open Fault
- PCR Stuck Closed Fault
- Auxiliary Battery depleted
- Auxiliary Battery disconnected
- Battery SOC below calibrated threshold
- Vehicle altitude is above a calibrated threshold