The ECM has several operating modes for fuel control, depending on the information that has been received from the sensors.
Starting Mode
When the ECM detects reference pulses from the Crankshaft Position sensor, the ECM will enable the fuel pump. The fuel pump runs and builds up pressure in the fuel system. The ECM then monitors the MAF, IAT, ECT, and the TP sensor signal in order to determine the required injector pulse width for starting.
Clear Flood Mode
If the engine is flooded with fuel during starting and will not start, the Clear Flood Mode can be manually selected. To select Clear Flood Mode, push the accelerator to Wide Open Throttle (WOT). With this signal, the ECM will completely turn Off the injectors and will maintain this stage as long as the ECM indicates a WOT condition with engine speed below 1,000 RPM.
Run Mode
The Run Mode has two conditions: Open Loop operation and Closed Loop operation. When the engine is first started and the engine speed is above 480 RPM, the system goes into an Open Loop operation. In an Open Loop operation, the ECM ignores the signals from the oxygen sensors and calculates the required injector pulse width based primarily on inputs from the MAF, IAT and ECT sensors.
In a Closed Loop, the ECM adjusts the calculated injector pulse width for each bank of injectors based on the signals from each oxygen sensor.
Acceleration Mode
The ECM monitors the changes in the TP and the MAF sensor signals in order to determine when the vehicle is being accelerated. The ECM will then increase the injector pulse width in order to provide more fuel for improved driveability.
Deceleration Mode
The ECM monitors changes in TP and MAF sensor signals to determine when the vehicle is being decelerated. The ECM will then decrease injector pulse width or even shut Off injectors for short periods to reduce exhaust emissions.
Battery Voltage Correction Mode
The ECM can compensate in order to maintain acceptable vehicle driveability when the ECM sees a low battery voltage condition. The ECM compensates by performing the following functions:
| • | Increasing the injector pulse width in order to maintain the proper amount of fuel being delivered |
| • | Increasing the idle speed to increase the generator output |
Fuel Shut-Off Mode
The ECM has the ability to completely turn off all of the injectors or selectively turn off some of the injectors when certain conditions are met. These fuel shut-off modes allow the Catera Engine to protect the engine from damage and also to improve the vehicle's driveability.
The ECM will disable all of the six injectors under the following conditions:
| • | Ignition Off (prevents engine run-on) |
| • | Ignition On but no ignition reference signal (prevents flooding or backfiring) |
| • | A high engine speed (above red line) |
| • | A high vehicle speed (above rated tire speed) |
| • | The extended high speed closed throttle coastdown (reduces the emissions and increases engine braking) |
The ECM will selectively disable the injectors under the following conditions:
| • | The Torque Management enabled (Transmission shifts or abusive maneuvers) |
| • | The Traction Control enabled (in conjunction with the front brakes applying) |
