Auto Stop Disengages Too Quickly - keywords auto autostop bas battery hybrid performance

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

A technician may state the Auto Stop feature does not last long enough.

When attempting to diagnose an Auto Start/Stop concern the technician should review the "Hybrid Data" list available in the engine ECM. This list contains several parameters that are directly related to the Auto Start/Stop feature. This can be found in the Tech2 under ECM/Data Display/Hybrid Data. Then look for "Eng Auto Start Reason" this parameter will list the last command that caused the Auto Start feature to engage. This parameter will be overwritten the next time Auto Start is engaged and replaced with the new/current command. These are the available listed parameters: BPP, APP, Trans Range Tim, Auto Stop Time, Hybrid Batt Stat, Aux TFP Pump, Coast Speed Low, Coast Speed High, BBC Low, Coast Speed Inc, 12V Batt Hi Amp, 12V Batt Lo Amp, Fault, ECT Low, Device Control, A/C Request, ECT High, Engine Control

Note: Some of the data (such as A/C or defrost engagement) will not be displayed when using the "Eng Auto Start Reason". The A/C inhibit has its own Tech2 menu/data stream titled "A/C Request Signal Yes or No" that can be viewed separately or in conjunction with other parameters using the graphing feature.

NOTE: MAXIMUM AUTO-STOP TIME IS 2 MINUTES UNDER IDEAL CONDITIONS.: With high outside temperature or humidity the Auto Stop feature can be maximized by using Recirculation in the economy a/c mode.

Many factors influence Auto stop duration. For example:

Normal AC mode or when defrost is selected auto/stop will be inhibited

Hybrid Battery SOC (state of charge) is below 70%

Battery discharge power capability is greater than minimum required for AutoStart (6200 watts).

12 volt battery is not fully charged

Brake is not fully applied or if the throttle is above 0

Vehicle is not fully stopped

Vehicle is in Reverse, Neutral or Park

Map sensor

Road Grade is less than 18 percent

Brake booster vacuum is too low

Hood switch is closed

High outside ambient temp or humidity -Engine coolant is less than 121°C (250°F)

Ambient outside temperature must be above -15°C (5°F)

Hybrid and powertrain component temperatures in hybrid operational ranges:

*Hybrid battery temperature is greater than 10°C (50°F) (approximate) and less than 50°C (122°F).

*Transmission fluid temperature is greater than 35°C (95°F) (ambient temperature less than 10°C (50°F).

*Transmission fluid temperature is greater than 20°C (68°F) (ambient temperature greater than 10°C ( 50°F)

*Transmission fluid temperature is less than 110°C (230°F).

*Engine coolant temperature is greater than 80°C (176°F) (ambient temperature less than 10°C ( 50°F).

*Engine coolant temperature is greater than 47°C (176°F) (ambient temperature greater than 10°C ( 50°F)

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.