Fuel Injector Measuring the electrical resistance of the solenoid winding enables an assessment to be made of the serviceability of an injector. Nominal resistance of the solenoid winding is 14.5 ± 0.7 Ω at 20 ° C. The ECM can detect electrical inconsistencies within each injector. It can also detect, via feedback from the HOS, mechanical faults such as blockage or leakage. The ECM will store a relevant fault code in these circumstances. The ECM will also store the engine speed, engine load and details of either the battery voltage, engine coolant temperature or intake air temperature. The precise details stored depend on the exact nature of the fault detected. T4 will also display data regarding injector operation via its live readings. Care must betaken when analysing this data, as the precise timings will vary considerably. Individual timings will be affected by any current engine load. Main Relay The ECM controls its own power supply, via the main relay in the engine compartment fusebox. When the ignition is turned to position II, the ECM provides aground to the main relay coil. The main relay then energises and connects the main power feed to the ECM. The ECM controls the main relay, and therefore its own power supply, so that when the ignition is turned off it can follow the power-down sequence, during which it records values from various sensors and writes adaptions into its memory, etc. The last action the ECM carries out before completing its power-down sequence is to turnoff the main relay. This will occur approximately 7 seconds after the ignition has been switched off, as long as the coolant temperature is not rising. For NAS vehicle with tank leakage detection and under some vehicle system fault conditions, this period could be extended up to 20 minutes. Failure of the main relay will result in the engine failing to start. The engine will stop immediately if the main relay fails while the engine is running. Fuel Pump Relay The ECM controls operation of the fuel pump via the fuel pump relay in the rear fusebox. The ECM switches the relay coil to earth to energise the relay when the ignition is first turned to position II. The relay remains energised during engine cranking and while the engine is running, but will be de-energised after approximately 2 seconds if the ignition switch remains in position II without the engine running. A fuel cutoff function is incorporated into the ECM to de-energise the fuel pump in a collision. The cutoff function is activated by a signal from the SRS DCU in the event of an airbag activation. The ECM receives an airbag activation signal from the SRS DCU on the CAN Bus. The fuel cutoff function can only be reset by using TestBook/T4. The ECM monitors the state of the wiring to the coil winding within the fuel pump relay. The ECM will store relevant fault codes if the ECM detects a problem. The ECM is notable to assess the state of the fuel pump circuit because it is isolated by the function of the relay. However, if the fuel pump circuit fails, or the pump fails to deliver sufficient fuel while the fuel level is above the minimum level, the ECM will store adaptive faults as it tries to increase the air/fuel ratio by increasing the pulse width of the injectors.
ENGINE MANAGEMENT SYSTEM – V8 DESCRIPTION AND OPERATION Failure of the fuel pump relay will result in the engine failing to start. If the fuel pump fails while the engine is running, the symptoms will be engine hesitation and engine misfire. These symptoms will worsen progressively until the engine stops. The ECM will store several fault codes under this condition.