P0271

DTC P0271: Injector 4 Control Circuit High Voltage

Wiring Diagram:

Circuit Description
The Engine Control Module (ECM) has four individual injector driver circuits, each of which controls an injector. When a driver circuit is grounded by the ECM, the injector is activated. The ECM monitors the current in each driver circuit. The ECM measures a voltage drop through a fixed resistor and controls it. The voltage on each driver is monitored to detect a fault. If the voltage is not what the ECM expects to monitor on the circuit, a Diagnostic Trouble Code (DTC) is set. This DTC detects a high voltage and/or a short to battery voltage conditions.

Conditions for Setting the DTC
- Engine is running.
- Ignition voltage is between 11 and 16 V.
- Enable time delay is greater than 0.5 seconds.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF after four consecutive validation cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- The DTC(s) can be cleared using the scan tool.

Diagnostic Aids
An injector driver circuit that is open or shorted to voltage will causes a DTC P0271 to set. It will also cause a misfire due to an inoperative injector. A misfire DTC should also be set indicating which injector is inoperative. Long-term and short-term fuel trims that are excessively high or low are a good indication of an injector malfunctioning. Refer to Fuel Injector Balance Test to check for malfunctioning injectors.

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Troubleshooting