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. Each Fuel Injector has a dedicated LSD circuit so that the injectors can be operated independently. The HSD drivers for Fuel Injectors 1, 2, 5 and 6 are grouped in the following pairs, Injector 1 with Injector 6, and Injector 2 with Injector 5. Fuel Injectors 3 and 4 are not grouped, they have their own dedicated HSD circuits. A short to voltage or ground on the HSD circuit of one of the Fuel Injectors that are grouped in pairs will set a supply voltage circuit DTC for both of the Fuel Injectors that are grouped. Fuel Injectors 3 and 4 will only set a supply voltage circuit DTC for the Fuel Injector that has the short in the HSD circuit since these injectors are not grouped.
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.
The fuel system is under a constant pressure (even with engine off). Before servicing any fuel system hose, fitting or line, fuel system pressure must be released. Refer to FUEL SYSTEM PRESSURE RELEASE .