Stop/Start System Diagnosis - Ess Equipped
For diagnostics of the Stop Start system, the scan tool can be used to review the Stop Start Data to help root cause a potential Stop Start concern.
With the scan tool, under BCM, Data display, review any data that will inhibit the ESS.
For diagnostics of the basic starting system, Refer to: DIAGNOSIS AND TESTING - STARTING SYSTEM .
For diagnostics of the Stop/Start system, the scan tool can be used to review the inputs/sensor values and DTCs to help root cause a potential Stop/Start concern.
With the scan tool, select OBDII monitors, OBDII, Engine Stop/Start Status, check for a "False" status to help root cause a potential Stop/Start concern.
Possible Reasons The Engine Does Not AUTOSTOP
Prior to engine shut down, the PCM will check many safety and comfort conditions to detect if they are fulfilled.
A Stop/Start Not Ready message and the inhibit reason may display in the Electronic Vehicle Information Center (EVIC).
| EVIC Warning Messages for ESS | |
|---|---|
| ESS EVIC Message | ESS EVIC Message Reason/Repair Action |
| Stop/Start Not Available | During ECM wake up and Stop/Start not ready at key On indicating engine off. |
| Stop/Start Active | Indicates engine is off during an Auto-Stop. |
| Stop/Start Not Ready Driver Seatbelt Unbuckled | Driver's seatbelt is unbuckled prior to an Auto-Stop. |
| Stop/Start Not Available Driver Not Detected | Driver Presence Detection Module indicates driver's seat is unoccupied for applications with removable doors only. |
| Stop/Start Not Ready Driver Door Open | Driver's door is open, prior or during an Auto-Stop. |
| Stop/Start Press Clutch or Shift To Neutral | Shifting into gear during an Auto-Stop without pressing the clutch. (For MTX vehicles only). |
| Stop/Start Restart Required Fault Detected | During an Auto-Stop/Auto-Start, the ECM/PCM detects a DTC calibrated to be an Engine Start inhibit trigger. Repair DTCs and retest. |
| Stop/Start Not Available Service Battery Radio display and functions may be inoperative to the customer. |
In order to allow the ESS Auto-Stop, the Battery State of Charge (SOC) must be greater than the threshold reported in the table. Refer to SOC . Main 12 Volt Battery does not successfully pass a load test or Battery is sulfated. Auxiliary Battery does not successfully pass a load test or Battery is sulfated. |
| Stop/Start Not Ready Battery Charging Radio display and functions may be inoperative to the customer. |
In order to allow the ESS Auto-Stop, the Battery State of Charge (SOC) must be greater than the threshold reported in the table. Refer to SOC . Main 12 Volt Battery does not successfully pass a load test or Battery is sulfated. Auxiliary Battery (if Equipped) does not successfully pass a load test or Battery is sulfated. |
| Stop/Start Fail | During engine running, ECM/PCM detects a DTC calibrated to be an Engine Off inhibit trigger. Repair DTCs and retest. |
| Stop/Start Not Available | Message Indicates "not ready" during engine running and any of the Engine Off AND Engine Start conditions are FALSE . |
| Stop/Start Ready | ATX: while vehicle is moving and during engine running, ESS ready to allow an Auto-Stop (all Engine Off AND Engine Start conditions are true) ESS will enter an Auto-Stop once TransReadyForESS = True, Master Cylinder input threshold, and Vehicle speed is below threshold. MTX: While vehicle is moving and engine running, ESS ready to allow an Auto-Stop (all Engine Off AND Engine Start conditions are true) once Vehicle speed is below threshold, Gear is in Neutral and Clutch pedal is released. |
| Stop/Start Off | Indicates ESS disable switch pressed, ESS is inhibited. No Auto-Stop while engine running. Auto-Start if ESS disable switch pressed during Auto-Stop. ESS disable switch status resets with every key cycle. |
| Stop/Start Not Ready Hood Open | Indicates hood is open. Inhibits Auto-Stop while engine running. |
| Stop/Start Not Ready Accelerator Depressed | Vehicle speed below Auto-Stopping threshold, brake pedal is pressed AND accelerator pedal is pressed. Inhibits Auto-Stop while engine running. Initiates an Auto-Start during an Auto-Stop. |
| Stop/Start Not Ready Battery Protection Mode Radio display and functions may be inoperative to the customer. |
With the scan tool, verify that the Battery State Of Function (SOF) status is not "False." In order to allow the ESS Auto-Stop, the Battery State of Function from the Intelligent Battery Sensor (IBS) must be greater than the threshold reported in the table. Refer to SOF |
| Stop/Start Not Ready Tow Active | When Tow/Haul mode is active, ESS is inhibited. Auto-Start is triggered if Tow/Haul Switch (if Equipped) is pressed during an Auto-Stop. |
| Stop/Start Not Ready 4Low Active | T-Case is in 4Wheel Low mode. Present on vehicles with T- Case (4Wheel Low). |
| Stop/Start Not Ready Too Steep | Indicates grade above calibrated threshold to allow Auto-Stop. Triggers an Auto-Start during an Auto-Stop if grade threshold is above +7% or below -10%. |
| Stop/Start Not Ready Cabin Cooling or Heating | Indicates HVAC demand via the CAN C Bus. |
| Stop/Start Not Ready Max Cooling or Heating | When HVAC max button is pressed by customer. Indicates HVAC demand via CAN C signal. Inhibits Auto-Stop while pressed. Triggers an Auto-Start if pressed during an Auto-Stop. |
| Stop/Start Not Ready Front Defrost Selected | Indicates Front Defrost active. Triggers an Auto-Start during an Auto-Stop and inhibits Auto-Stop if active during engine running. |
| Stop/Start Not Ready Turned Steering Wheel | Indicates steering wheel is being turned. Inhibits Auto-Stop if present during engine running. Triggers Auto-Starts if active during and Auto-Stop. |
| Stop/Start Not Ready Engine Temp Too Low | Indicates either coolant, or oil, or catalyst engine temperature is lower than calibrated threshold. Inhibits Auto-Stop during engine running and triggers an Auto-Start during an Auto-Stop event. For engine coolant temperature. Refer to: MINIMUM ENGINE COOLANT TEMPERATURE TO ALLOW AUTOSTOP EVENT and MINIMUM ENGINE OIL TEMPERATURE TO ALLOW AUTOSTOP EVENT Minimum Catalyst Temperature to allow an ESS Auto-Stop event is (440°C) 824°F. |
| Stop/Start Not Ready DEF RGN (if Equipped) | During engine running, ECM inhibits Auto-Stop when Regen is active. |
| Stop/Start Not Ready Service Battery Vehicle Shut Off | During a failure of the Power Control Relay (PCR). After an Auto-Stop: If Power Control Relay between Cranking Battery and Auxiliary Battery is stuck open, vehicle shuts off within minutes. |
The engine will NOT Auto-Stop unless ALL conditions below are TRUE .
If ANY of the conditions below are NOT TRUE Auto-Stop is INHIBITED .
| ESS Allow Conditions for Auto-Stop | |
|---|---|
| Condition | Operating Range |
| Outside Ambient temperature | Greater than 10°F (-12°C) or less than 110°F (43°C) |
| Driver seatbelt | Buckled |
| Driver door | Closed |
| Driver seat pad Driver Presence Detection Module (if equipped) | Occupied - when equipped (on vehicles with removable doors) |
| Hood | Fully closed (2 Hood Ajar Switch Inputs) |
| Accelerator pedal | Released |
| Grade -too steep of an incline/decline | Lesser than +7% OR greater than -10% |
| Engine operating temperature | Minimum acceptable range: Coolant temperature greater than a calibrated threshold (Function of ambient temp) Engine Oil temperature is greater than a calibrated threshold (Function of ambient temp) Catalyst temperature is greater than a calibrated threshold (Function of ambient temp) Maximum acceptable range: Coolant temperature below a calibrated threshold 239°F (115°C) Engine Oil temperature below a calibrated threshold 239°F (115°C) Catalyst temperature below a calibrated threshold 1742°F (950°C) |
| Transfer Case Selection | 4WD LO = Off Neutral = Off |
| Manual Paddle shifter | Not selected/active/pressed |
| Shifter position | Drive (NAFTA ATX) Neutral (NAFTA MTX) |
| Brake Master Cylinder pressure | Above a calibrated threshold (ATX only) |
| Hill start assist | Hill start assist brake pressure above calibrated threshold |
| ESS related OBD faults | No Active OBD DTCs |
| Brake Booster Vacuum | 29.9 kPa (4.34 PSI) |
| Steering Angle | Below 135 degrees |
| Tow Haul Mode | Off |
| ESS Disable Button | Not pressed |
| PPPA (Parallel Perpendicular Park Assist) | Not active |
| Altitude | Barometric pressure above: 72 KPa (less than 9, 00 ft.) |
| Brake Pedal | Pressed (while maintaining steady Brake Pedal pressure applied by driver) |
| ABS Module | Anti-lock brake system is not active |
| Engine Speed | 1100 RPM |
| ACC+ | Stop/Start allowed |
| Engine run time | 2 seconds |
| Vehicle speed | 0 MPH\0 km\h (ATX) |
| Threshold vehicle speed exceeded since last engine Auto-Start | 5 MPH |
| 12 volt Battery Parameters | Voltage more than 11.5 volts SOC above 65% Temperature below 140°F (60°C) |
It may be possible for the vehicle to be driven several times without the Stop/Start system going into a Stop/Start ready state under more extreme conditions of the items listed above.
When it comes to Stop/Start, the PCM allows the engine Auto-Start during an Auto-Stop event when any of the below conditions are TRUE .
| ESS Allow Conditions for Auto-Start | |
|---|---|
| Condition | Operating Range |
| Ambient temperature | Less than 10°F (-12°C) or greater than 110°F (43°C) |
| Shifter Position | For NAFTA : Out of Drive or M-Gate For EMEA : Neutral / Reverse |
| Accelerator Pedal | Pressed |
| HVAC mode: |
|
| HVAC blower speed | Max blower speed selected or blower speed incremented |
| Grade-too steep of an incline/decline | Greater than +7% OR lesser than -10% |
| Engine operating temperature | Minimum acceptable range: Coolant temperature less than a calibrated threshold (Function of ambient temp) Engine Oil temperature is less than a calibrated threshold (Function of ambient temp) Catalyst temperature is less than a calibrated threshold (Function of ambient temp) Maximum acceptable range: Coolant temperature above a calibrated threshold 239°F (115°C) Engine Oil temperature above a calibrated threshold 239°F (115°C) Catalyst temperature above a calibrated threshold 1742°F (950°C) |
| Stop/Start Auto-Stop time active | Exceeded 5 minute timeout |
| Transfer Case Selection | 4WD LO = ON Neutral = ON |
| Manual Paddle shifter | Active/Pressed during Auto-Stop |
| Shifter position | Auto-Start when shifter moved out of Drive |
| Brake Master Cylinder pressure | Below a calibrated threshold (Below 3bar) Or below a calibrated pressure gradient threshold (ATX only) |
| Hill Start Assist | Hill Start Assist brake pressure below calibrated threshold |
| ESS related OBD Faults | Calibrated active to allow Auto-Start Example: U0131-00 active DTC |
| Brake Booster Vacuum | 29.9 kPa (4.34 PSI) |
| Steering Angle | Above 135 degrees |
| Tow Haul Mode | On |
| ESS Disable Button | Pressed |
| PPPA (Parallel Perpendicular Park Assist) | Activated |
| Brake Pedal | Released |
| ACC+ | Cancelled/disengaged |
| Vehicle speed | Above 0 MPH/0 km\h (ATX) Above 1.5 MPH/3 km\h (MTX) |
| 12V Battery Parameters | Voltage Less than 11.5 V (trigger Auto-Start when below 11.5 V) SOC Below 65% Temperature Above 140°F (60°C) Main 12 Volt Battery does not successfully pass a load test or Battery is sulfated. Auxiliary Battery does not successfully pass a load test or Battery is sulfated. |
SOC
| IBS SOC Temperature | Minimum SOC to allow ESS Auto-Stop |
| (-20°C) -4°F | 100 |
| (-16°C) 3.2°F | 100 |
| (-15°C) 5°F | 80 |
| (-1°C) 30.2°F | 80 |
| (0°C) 32°F | 70 |
| (15°C) 59°F | 70 |
| (35°C) 95°F | 70 |
| (50°C) 122°F | 70 |
| (59°C) 138.2°F | 70 |
| (60°C) 140°F | 100 |
| (80°C) 176°F | 100 |
SOF
| IBS SOF Temperature | Minimum SOF to allow the ESS Auto-Stop |
| (-15°C) 5 °F | 7 |
| (-5°C) 23°F | 7 |
| (5°C) 41°F | 7 |
| (15°C) 59°F | 7 |
| (25°C) 77°F | 7 |
| (35°C) 95°F | 7 |
| (45°C) 113°F | 7 |
| (60°C) 140°F | 7 |
MINIMUM ENGINE COOLANT TEMPERATURE TO ALLOW AUTOSTOP EVENT
| Minimum Engine Coolant Temperature To Allow Auto-Stop Event | Ambient Temperature |
| (80°C) 176 °F | (-16°C) 3.2 °F |
| (70°C) 158°F | (0°C) 32°F |
| (60°C) 140°F | (10°C) 50°F |
| (55°C) 131°F | (15°C) 59°F |
| (45°C) 39.2°F | (20°C) 68°F |
| (40°C) 104°F | (25°C) 77°F |
| (40°C) 104°F | (30°C) 86°F |
| (40°C) 104°F | (35°C) 95°F |
| (40°C) 104°F | (40°C) 104°F |
MINIMUM ENGINE OIL TEMPERATURE TO ALLOW AUTOSTOP EVENT
| Minimum Engine Oil Temperature To Allow Auto-Stop Event | Ambient Temperature |
| (50°C) 122 °F | (0°C) 32°F |
| (40°C) 104°F | (5°C) 41°F |
| (35°C) 95°F | (10°C) 50°F |
| (30°C) 86°F | (15°C) 59°F |
| (25°C) 77°F | (20°C) 68°F |
| (25°C) 77°F | (25°C) 77°F |
| (25°C) 77°F | (30°C) 86°F |
| (25°C) 77°F | (35°C) 95°F |
| (25°C) 77°F | (40°C) 104°F |