Theory Of Operation

The Fuel Injectors are unique to the high pressure Direct Injection fuel system. The Fuel Injectors are controlled by the Powertrain Control Module (PCM) using both a High Side Driver (HSD) and Low Side Driver (LSD) circuit for each Fuel Injector. The PCM operates the Fuel Injectors by turning on the HSD and LSD circuits simultaneously. The PCM uses a banked circuit topology on the HSD circuits. This means that Fuel Injectors 1 and 4 share a common HSD source inside the PCM and Fuel Injectors 2 and 3 share another common HSD source. Each Fuel Injector has a dedicated LSD circuit so that the injectors can be operated independently.

There are two types of diagnostics performed on the Fuel Injectors.

• Circuit Fault Detection:  The PCM performs circuit fault detection on the HSD and LSD control circuits. The circuits are monitored for opens, shorts to voltage and ground, and a short across the Fuel Injector coil. The correlating circuit fault will set in the PCM if any of these conditions are detected. Both driver circuits are capable of setting a circuit open, low or high fault.
• Fuel Injector Performance Detection:  The PCM monitors the current feedback signal for each individual Fuel Injector during operation. The PCM will adjust the energizing time of the Fuel Injector based on this feedback. If the PCM detects an implausible current feedback signal, a Fuel Injector performance fault will set. The PCM also monitors the base adaptation of the Fuel Injector over time. This is done to re-adjust various thresholds considering aging of the Fuel Injector. If the base adaptation is beyond a calibrated threshold, a Fuel Injector performance fault will set.