Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Typical Scan Tool Data
Parameter Display | Autostop Inhibit or Autostart Reason |
|---|---|
4WD Low | Transfer case selector is in 4 wheel drive Low Range |
Autostart/stop Override | Scan tool Output Control active |
Aux. Trans. Pump With ECM Ambient Air Temperature less than 10°C (50°F)¹ | DTC P0C2B or P2797 set OR ECM Ambient Air Temperature less than 10°C (50°F)¹ |
Aux. Trans. Pump With ECM Ambient Air Temperature 10°C (50°F) - 15°C (59°F)¹ | DTC P0C2B or P2797 set OR TFT less than 35°C (95°F) or greater than 95°C (203°F) |
Aux. Trans. Pump With ECM Ambient Air Temperature 15°C (59°F) - 20° (68°F)¹ | DTC P0C2B or P2797 set OR TFT less than 25°C (77°F) or greater than 95°C (203°F) |
Aux. Trans. Pump With ECM Ambient Air Temperature greater than 20° (68°F)¹ | DTC P0C2B or P2797 set TFT less than 20°C (68°F) or greater than 95°C (203°F) |
Battery Pack Temp | Hybrid Batt Min Cell Temp is less than 10°C (50°F) OR Hybrid Batt Max Cell Temp is Greater than 47°C (116°F) |
Drvr Axle Torque Request | Depression of the accelerator pedal has exceeded the torque capability for electric-only or EV Mode propulsion |
ECM Request | ECM DTC testing in progress or ECM DTCs present |
ECT - High Limit | ECT 110°C (230°F) or greater Autostop if cools down to 90°C (194°F) once high temperature limit has been reached. |
ECT - Low Limit With ECM Ambient Air Temperature 10°C (50°F) - 20°C (68°F)¹ | ECT less than 68°C (154°F) Autostart if cools down to 60°C (140°F) once high temperature limit has been reached |
ECT - Low Limit With ECM Ambient Air Temperature greater than 20°C (68°F)¹ | ECT less than 49°C (120°F) Autostart if cools down to 44°C (111°F) |
Hood Position | Open or faulted |
Hybrid Batt. Pack Voltage | 250V or less When Autostop limit has been achieved, Autostart if voltage drops to 200V |
Hybrid Batt. Pack Power | 15kW or less Power is dependent upon battery temperature. Observe Hybrid Battery Temperature parameters when Hybrid Batt. Pack Power inhibits Autostop. When Autostop limit has been achieved, Autostart if power drops to 12kW |
Hybrid Battery SOC | 50% or less When Autostop limit has been achieved, Autostart if SOC drops to 46% |
ICE Run Time With ECM Ambient Air Temperature 10°C (50°F) - 15°C (59°F)¹ | Less than 20 seconds since ignition crank |
ICE Run Time With ECM Ambient Air Temperature greater than 15°C (59°F)¹ | Less than 5 seconds since ignition crank |
Ignition Crank | Ignition key not in RUN -- engine remote started |
IMS Range | Gear Selector in Reverse or Manual |
Invalid Signal | The HPCM has monitored invalid data and has stored a DTC |
Inverter Temperature | Greater than 65°C (149°F) When Autostop limit has been achieved, Autostart at 70°C (158°F) |
Min. Hybrid Batt. Module Voltage | The minimum hybrid battery module pair voltage is less than 14 volts. When Autostop limit has been achieved, Autostart if voltage drops to 12V. |
Motor Temperature | Greater than 165°C (329°F) When Autostop limit has been achieved, Autostart at 170°C (338°F) |
Operating Conditions | The current driving conditions inhibit autostop operation. This parameter should be displayed along with other inhibit reasons such as Drvr Axle Torque Request |
Reduced Engine Power | The ECM is limiting engine torque output and has stored a DTC |
Remote Start Request | The vehicle has been started by remote transmitter |
Reverse Inhibit Command | The transmission gear selector has been placed in the Reverse position |
Run/Crank Mode | SDGM Power mode is not in RUN |
System Voltage | 12V system voltage is out of range as monitored by the HPCM |
Vehicle Speed | Vehicle speed is greater than allowed |
¹The HPCM monitors the ECM Ambient Air Temperature parameter to determine outside temperature. the ECM will default to 0°C (32°F) ambient air temperature if an IAT sensor DTC is present. | |
Circuit/System Description
This vehicle does not use a 12V starter motor to crank the internal combustion engine (ICE). A much more powerful 300V motor/generator located within the transmission is utilized to crank the engine. The 300V motor/generator can rotate the engine to operating speed, 800 RPM, within just a few hundred milliseconds. The 300V motor/generator allows near-instant starting of the engine. Once started, engine operation may cycle between Autostop, engine off, and Autostart, engine running, for the duration of the drive trip.
Autostop/Autostart
The Two-Mode Hybrid vehicle does not require ICE operation at all times. After a successful engine start, the hybrid powertrain control module (HPCM) may turn off the engine, or Autostop, when not required for the current vehicle conditions. The engine will remain off while in Autostop mode, until such time that vehicle conditions require the engine to run. The near-instant starting of the engine from Autostop mode is called Autostart.
Autostop Conditions
Numerous conditions must all be within acceptable limits in order for the HPCM to allow the Autostop hybrid mode. The Typical Scan Tool Data information lists the vehicle conditions required for Autostop operation.
Diagnostic Aids
A chime will sound if the drivers door is opened while in Autostop as a reminder that the engine is not in the OFF mode.
Engine OFF and AUTO STOP modes are indicated on the tachometer display.
| ⇒ | When the tachometer needle indicates OFF, the engine is not running and will remain Off until the ignition key is placed in the Crank position or a remote vehicle start request is received from the keyless entry transmitter. Autostop is not allowed with a remote vehicle start. |
| ⇒ | When the tachometer needle indicates AUTO STOP, the engine is not running but may Autostart at any time without notice. |
Reference Information
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Circuit/System Verification
- Hood closed, start the engine with the ignition key and allow to idle.
- Monitor engine operation and the tachometer display for 5 minutes.
- The vehicle should enter the Autostop hybrid mode.
| ⇒ | If the vehicle operates in the Autostop hybrid mode, the system is operating normally. |
| ⇒ | If the vehicle cycles rapidly in and out of the Autostop hybrid mode, test the auxiliary transmission fluid pump pressure. Refer to Line Pressure Check. |
| ⇒ | If the vehicle does not operate in the Autostop hybrid mode, continue to Circuit/System Testing. |
Circuit/System Testing
- Verify no HPCM or ECM DTCs are set. Repair any HPCM or ECM DTCs prior to performing this diagnostic procedure.
- Engine at idle, observe the HPCM Autostop Inhibit Reasons scan tool parameter.
- Compare the parameter display to the Typical Scan Tool Data information.
- Identify which Autostop inhibit conditions have prohibited Autostop operation. An Inhibit condition will display YES on the scan tool.
- Determine if the Autostop inhibit conditions are the result of normal operating conditions or the result of a fault condition.
| ⇒ | Repair the conditions that are the result of a fault condition. For example, a hood switch that indicates hood status as open when the hood is actually closed. |
| ⇒ | Advise the vehicle operator of the normal operating and environmental conditions that will inhibit Autostop. For example, advise that Autostop is disabled when hybrid Battery Pack temperature is less than 10°C (50°F). |
