Diagnosis And Testing - Engine Stop Start
For diagnostics of the starting system, please. Refer to DIAGNOSIS AND TESTING .
For diagnostics of the Engine Stop Start (ESS) system, use the diagnostic scan tool to review the inhibitors menu to help root cause a potential ESS concern.
Potential AUTOSTOP Inhibitors
Prior to engine shut down, the system will check many safety and comfort conditions to see if they are fulfilled. In following situations the engine will not stop:
- Drivers seat belt is not buckled.
- Battery or outside temperature is less than -15°C (5°F) or greater than 60°C (140°F).
- Actual cabin temperature is significantly different than temperature set on Auto Heating Ventilation and Air Conditioning (HVAC) settings.
- HVAC is set to full defrost mode.
- Engine has not reached normal operating temperature.
- Battery discharged.
- When driving in (R ) REVERSE.
- Hood is open for further information on the Hood Ajar Switch operation and diagnostics. Refer to SWITCH, HOOD AJAR, DESCRIPTION .
- Vehicle is in Four Wheel Drive (4WD) low transfer case mode.
It may be possible for the vehicle to be driven several times without the ESS system going into an ESS READY state under more extreme conditions of the items listed above.
For a more technical and detailed explanation of AutoStop, review the following inhibitors.
AutoStop events are allowed when:
- Accelerator pedal is in the rest position.
- HVAC control allows an auto stop event. The AC load can not be in a high demand mode of operation.
- Battery state (charge 65%, function 8 volts, health 40 ampere hour) is within an acceptable range.
- Current master cylinder brake pressure exceeds the required Hill Speed Assist (HSA) brake pressure and is sufficient to hold the vehicle on a grade.
- Electronic Stability Control (ESC) is not requesting control.
- Fuel level is greater than the minimum fuel level threshold.
- Both hood switches indicate the hood is closed.
- Predefined On-Board Diagnostics (OBD) faults are not present.
- Vehicle occupants are not attempting a vehicle exit maneuver.
- Absolute barometric pressure is within range. Barometric pressure is greater then a minimum of 605KPa.
- Brake booster is sufficient to maintain master cylinder pressure with current applied pedal force. Minimum 205Ka.
- Starter motor engagement has not exceeded frequency use limits.
- Vehicle speed is at 0.
- Steering angle has not exceeded the prescribed range.
- Steering torque is less than the prescribed value.
- Ambient air temperature is within the prescribed range of -17°C (1°F) - 40°C (104°F).
- Catalyst temperature is within the prescribed range of 66°C (150°F) - 510°C (950°F).
- Engine Coolant Temperature (ECT) is within the prescribed range.
- Engine oil temperature is within the prescribed range of 40°C (104°F) - 110°C (230°F).
- Antilock Brake System (ABS) is not active.
- Transfer case is not engaged in 4WD Low.
- Vehicle is not in tow haul mode.
- Vehicle is in valid target gear and brake switch combination.
- Threshold vehicle speed exceeded or timeout since last shift out of reverse.
- Transmission is in a ready state.
- Battery temperature is within the prescribed range of -15°C (5°F) or greater than 60°C (140°F).
- Engine speed is below a set threshold of 1000 Revolutions Per Minute (RPM).
- Engine runtime is greater then threshold of three seconds.
- ESS disable switch is not active.
- Flexible fuel learn mode is not active.
- Vehicle is not on a steep grade.
- Threshold vehicle speed exceeded since last engine start is 12 km/h (8 mph).
Conditions that will cause the engine to start automatically while in ESS AUTO STOP ACTIVE mode:
- Actual cabin temperature is significantly different than temperature set in Auto HVAC.
- HVAC is set to full defrost mode.
- ESS AUTO STOP TIME ACTIVE exceeds five minutes.
- Battery voltage drops too low.
- Low brake vacuum found after several brake pedal applications.
- Vehicle is moving faster then 3 km/h (5 mph).
- ESS OFF switch is pressed.
- 4WD is put into 4LO mode.
ESS AutoStarts can occur when any of the conditions are made active:
- Accelerator pedal is in the rest position.
- HVAC control is allows an ESS event.
- Battery State (charge, function, health) is within acceptable range.
- Current master cylinder brake pressure exceeds the required HSA brake pressure and is sufficient to hold the vehicle on a grade.
- ESC system is not requesting control.
- Fuel level is greater than the minimum fuel level threshold.
- Both hood switches indicate hood is closed.
- Predefined OBD faults are not present.
- Vehicle occupants are not attempting a vehicle exit maneuver.
- Absolute barometric pressure is within range.
- Brake booster pressure is sufficient to maintain master cylinder pressure with current applied pedal force.
- Starter motor engagement has not exceeded prescribed frequency of use.
- Vehicle speed is at 0.
- Steering angle has not exceeded the prescribed range.
- Steering Torque is less than the prescribed value.
- Ambient air temperature is within the prescribed range of -17°C (1°F) - 40°C (104°F).
- Catalyst temperature is within the prescribed range of 66°C (150°F) - 510°C (950°F).
- ECT is within the prescribed range.
- Engine oil temperature is within the prescribed range of 40°C (104°F) - 110°C (230°F).
- ABS System is not active.
- Transfer case mode is not in 4WD Low.
- Vehicle is not in tow haul mode.
- Vehicle is in valid target gear and brake switch state combination.
- Threshold vehicle speed exceeded or timeout since last shift out of reverse.
- Transmission is in a ready state.
- Battery temperature is within the prescribed range of -15°C (5°F) or greater than 60°C (140°F).
- Engine speed is below a set threshold.
- Threshold vehicle speed exceeded since last engine start.
- Engine runtime greater than threshold.
- ESS disable switch is not active.
- Flexible fuel learn mode not active.
- Vehicle is not on a grade.
ESS AutoStarts allowed to occur when any of the conditions are made active:
- Accelerator pedal is not in the rest position.
- HVAC control is active.
- Battery state (charge, function, health) is out of range.
- Current master cylinder brake pressure does not have enough HSA brake pressure.
- ESC system is requesting control.
- Fuel level is lower than the minimum fuel level threshold.
- One or both hood switches indicate hood is open.
- Predefined OBD faults are present.
- Absolute barometric pressure is out of range.
- Brake booster pressure is insufficient to maintain master cylinder pressure with current applied pedal force.
- Starter motor engagement has exceeded prescribed frequency of use.
- Vehicle speed is above 0.
- Steering angle has exceeded the prescribed range.
- Steering torque is more than the prescribed value.
- Ambient air temperature is outside the prescribed range of -17°C (1°F) - 40°C (104°F).
- Catalyst temperature is outside the prescribed range of 66°C (150°F) - 510°C (950°F).
- Coolant temperature is outside the prescribed range.
- Engine oil temperature is outside the prescribed range of 40°C (104°F) - 110°C (230°F).
- ABS system is active.
- Transfer case mode is in 4WD Low.
- Vehicle is in tow haul mode.
- Transmission is not in a ready state.
- Battery temperature is out of the prescribed range of -15°C (5°F) or greater than 60°C (140°F).
- ESS disable switch is active.
- Flexible fuel learn mode is active.
The above conditions can restart the vehicle as long as:
- Completed initial engine key start.
- Occupant sensing allow engine start condition met.
- OBD allow engine start condition met.
- Vehicle hood closed.
System Malfunction/Indications:
If there is a malfunction in the ESS system, the system will not shut down the engine. A SERVICE STOP/START SYSTEM message will appear in the Electronic Vehicle Information Center (EVIC).
Messages will appear in the Instrument Cluster Panel (ICP) indicating ESS activity, Some of those messages are:
- Stop/Start Not Ready Driver Seatbelt Unbuckled
- Stop/Start Restart Req'd Seatbelt Unbuckled and Door Open
- Stop/Start Not Ready Driver Door Open
- Stop/Start To Restart Press Clutch or Shift to Neutral+
- Stop/Start Unavailable Service Battery (Battery SOH is low)
- Stop/Start Not Ready Battery Charging
- Stop/Start Not Ready 4WD / Low Range Selected
- Stop/Start Not Ready Due to Outside Temperature
- Stop/Start Not Ready Cabin Cooling or Heating
- Stop/Start Not Ready Battery Protection Mode (Battery Temp Too High/Low)