Electronic Throttle Control (ETC) System Strategy
The torque based ETC strategy was developed to improve fuel economy and to accommodate variable camshaft timing (VCT). This is possible by not coupling the throttle angle to the driver pedal position. Uncoupling the throttle angle (produce engine torque) from the pedal position (driver demand) allows the powertrain control strategy to optimize fuel control and transmission shift schedules while delivering the requested wheel torque.
The ETC monitor system is distributed across 2 processors within the PCM: the main powertrain control processor unit (CPU) and a separate monitoring processor. The primary monitoring function is carried out by the independent plausibility check (IPC) software, which resides on the main processor. It is responsible for determining the driver-demanded torque and comparing it to an estimate of the actual torque delivered. If the generated torque exceeds driver demand by a specified amount, appropriate corrective action is taken.
ETC SYSTEM WITH A 3-TRACK APP SENSOR FAILURE MODE AND EFFECTS MANAGEMENT:
| Effect | Failure Mode a |
|---|---|
| No Effect on Driveability | A loss of redundancy or loss of a non-critical input could result in a concern that does not affect driveability. The powertrain malfunction indicator (wrench) illuminates, but the throttle control and torque control systems function normally. A DTC is set to indicate the component or circuit with the concern. |
| Disable Speed Control | If certain concerns are detected, speed control is disabled. Throttle control and torque control continue to function normally. |
| RPM Guard with Pedal Follower | In this mode, torque control is disabled due to the loss of a critical sensor or PCM concern. The throttle is controlled in pedal-follower mode as a function of the pedal position sensor input only. A maximum allowed RPM is determined based on the position of the accelerator pedal (RPM Guard). If the actual RPM exceeds this limit, spark and fuel are used to bring the RPM below the limit. The powertrain malfunction indicator (wrench) and the MIL illuminate in this mode and a DTC for an ETC-related component is set. EGR, VCT, and IMRC outputs are set to default values. |
| RPM Guard with Default Throttle | In this mode, the throttle plate control is disabled due to the loss of throttle position, the throttle plate position controller, or other major electronic throttle body concern. Depending on the concern detected, the throttle plate is either commanded to the default (limp home) position or the motor is disabled and the spring returns the throttle plate to the default (limp home) position. A maximum allowed RPM is determined based on the position of the accelerator pedal (RPM Guard). If the actual RPM exceeds this limit, spark and fuel are used to bring the RPM below the limit. The powertrain malfunction indicator (wrench) and the MIL illuminate in this mode and a DTC P2110 is set. EGR, VCT, and IMRC outputs are set to default values. |
| RPM Guard with High Forced Idle | This mode is caused by the loss of 2 or 3 pedal position sensor inputs due to sensor, wiring, or PCM concerns. The system is unable to determine driver demand, and the throttle is controlled to a fixed high idle airflow. There is no response to the driver input. The maximum allowed RPM is a fixed value (RPM Guard). If the actual RPM exceeds this limit, spark and fuel are used to bring the RPM below the limit. The powertrain malfunction indicator (wrench) and the MIL illuminate in this mode and a DTC P2104 is set. EGR, VCT, and IMRC outputs are set to default values. |
| Shutdown | If a significant processor concern is detected, the monitor forces vehicle shutdown by disabling all fuel injectors. The powertrain malfunction indicator (wrench) illuminates in this mode and a DTC P2105 is set. |
a ETC illuminates or displays a message on the message center immediately; MIL illuminates after 2 driving cycles
ETC SYSTEM WITH A 2-TRACK APP SENSOR FAILURE MODE AND EFFECTS MANAGEMENT:
| Effect | Failure Mode |
|---|---|
| No Effect on Driveability | A loss of redundancy or loss of a non-critical input could result in a concern that does not affect driveability. The powertrain malfunction indicator (wrench) and the MIL do not illuminate. However, speed control and power take off (PTO) may be disabled. A DTC is set to indicate the component or circuit with the concern. |
| Delayed APP Sensor Response with Brake Override | This mode is caused by the loss of 1 APP sensor input due to sensor, wiring, or PCM concerns. The system is unable to verify the APP sensor input and driver demand. The throttle plate response to the APP sensor input is delayed as the accelerator pedal is applied. The engine returns to idle RPM whenever the brake pedal is applied. The powertrain malfunction indicator (wrench) illuminates, but the MIL does not illuminate in this mode. An APP sensor related DTC is set. |
| Time-Based Driver Demand with Brake Override | This mode is caused by the loss of one brake pedal position (BPP) and one APP sensor input or both APP sensor inputs due to sensor, wiring, or PCM concerns. The system is unable to determine driver demand. There is no response when the accelerator pedal is applied. The engine returns to idle RPM whenever the brake pedal is applied. When the brake pedal is released, the PCM slowly increases the APP signal to a fixed value. The powertrain malfunction indicator (wrench) illuminates, but the MIL does not illuminate in this mode. An APP or BPP sensor related DTC is set. |
| RPM Guard with Pedal Follower | In this mode, torque control is disabled due to the loss of a critical sensor or PCM concern. The throttle is controlled in pedal-follower mode as a function of the APP sensor input only. A maximum allowed RPM is determined based on the position of the accelerator pedal (RPM Guard). If the actual RPM exceeds this limit, spark and fuel are used to bring the RPM below the limit. The powertrain malfunction indicator (wrench) and the MIL illuminate in this mode and a DTC for an ETC-related component is set. EGR, VCT, and IMRC outputs are set to default values and speed control is disabled. |
| RPM Guard with Default Throttle | In this mode, the throttle plate control is disabled due to the loss of both TP sensor inputs, loss of throttle plate control, stuck throttle plate, significant processor concerns, or other major electronic throttle body concern. The spring returns the throttle plate to the default (limp home) position. A maximum allowed RPM is determined based on the position of the accelerator pedal (RPM Guard). If the actual RPM exceeds this limit, spark and fuel are used to bring the RPM below the limit. The powertrain malfunction indicator (wrench) and the MIL illuminate in this mode and a DTC for an ETC-related component is set. EGR, VCT, and IMRC outputs are set to default values and speed control is disabled. |
ELECTRONIC THROTTLE MONITOR OPERATION:
| DTCs a | |
|---|---|
| P060X, P061X | PCM processor concern (MIL, powertrain malfunction indicator [wrench]) |
| P2104 (ETC system with a 3-track APP sensor) | ETC FMEM - forced idle, 2 or 3 pedal sensor concerns (MIL, powertrain malfunction indicator [wrench]) |
| P2105 (ETC system with a 3-track APP sensor) | ETC FMEM - forced engine shutdown; PCM concern (MIL, powertrain malfunction indicator [wrench]) |
| P2110 (ETC system with a 3-track APP sensor) | ETC FMEM - forced limited RPM; Concern with both TP sensors; throttle plate position control concern (MIL, powertrain malfunction indicator [wrench]) |
| U0300 | ETC software version mismatch between processors internal to the PCM (non-MIL, powertrain malfunction indicator [wrench]) |
a Monitor execution is continuous. Monitor false detection duration is less than 1 second to register a concern.