BMW fault 2E45 - HPFI control unit (line 4) activation
P0271 · P0270 · P0204
Description
2E45 is logged by the DME when the activation circuit for high-pressure fuel injector line 4 reports a fault. The HPFI control unit is the injector driver built into the DME, responsible for switching current to the direct fuel injector on each line. Monitoring runs while the engine is above 40 rpm with battery voltage in the normal operating range.
This code has 3 variants with different causes and fixes. Pick the one your scanner reported.
2E45 / P0271 Overcurrent
The DME measured current above 3.8 A on the injector line 4 activation pin (pin 3-11) while the engine was running above 40 rpm. The activation circuit is drawing more current than the driver stage expects, consistent with a low-resistance fault on the circuit.
Symptoms (4)
- MIL illuminated after two drive cycles.
- Rough running and misfire.
- Possible reduced-power message.
- Misfire on two cylinders per the DME's protection strategy.
Common Causes (3)
- Shorted injector winding causing excessive current draw.
- Wiring shorted to B+ between the DME and the injector.
- Failed DME injector driver on the line 4 output stage.
Diagnosis Steps (5)
- Read fault memory, noting active vs. stored status and companion faults.
- Unplug the line 4 injector, clear the code, and start the engine. Overcurrent replaced by open-circuit: injector at fault. Overcurrent persists: harness or DME.
- Measure injector resistance and compare against the other injectors on the bank. A significantly lower value confirms a shorted winding.
- Check the line 4 harness for chafing or contact with battery-positive wiring.
- If both harness and injector pass, the DME driver has failed internally.
Resolution
Replace a shorted injector and code its flow-correction value into the DME. If the harness is at fault, repair the damaged section and address the routing to prevent recurrence. A failed DME driver requires module replacement with programming to the vehicle. Clear codes and rescan after a drive cycle.
2E45 / P0270 Open circuit
The DME measured voltage between 4.4 V and 5.6 V at pin 3-11 while the engine was running. The pin is floating at mid-rail voltage, meaning the connection between the DME and the line 4 injector is broken.
Symptoms (4)
- MIL illuminated after two drive cycles.
- Complete misfire on the affected cylinder with no fuel delivery.
- Power loss and rough idle that does not improve with temperature.
- Misfire on two cylinders per the DME's protection strategy.
Common Causes (4)
- Partially seated injector connector, especially after recent service.
- Broken or corroded activation wire.
- Open injector winding.
- Bent or backed-out pin at the DME connector.
Diagnosis Steps (5)
- Read fault memory, noting active vs. stored status and any companion faults.
- Reseat the line 4 injector connector after inspecting for corrosion. Clean with contact cleaner if needed.
- Test wire continuity from the injector connector to DME pin 3-11. Near 0 ohms is a good result.
- Measure injector winding resistance. An open winding reads OL.
- Inspect the DME connector at pin 3-11 for terminal damage.
Resolution
Reseat a loose connector and check that the latch engages fully. For a broken wire, use a soldered or crimped splice with adhesive heat-shrink and route clear of stress points. An open injector requires replacement with flow-value coding into the DME. Clear the fault and rescan after a drive cycle.
2E45 / P0204 Short to ground
The DME measured voltage below 2.1 V at pin 3-11 when battery voltage should be present on the activation line. An external ground path is holding the pin low. P0204's OBD-II label reads "Cylinder 4 Injector Circuit/Open," but the BMW monitoring condition (sustained pin-low) is consistent with a hard short to ground.
Symptoms (4)
- MIL illuminated after two drive cycles.
- Severe misfire on the affected cylinder.
- Possible engine protection mode for heavy shorts.
- Possible blown injector supply fuse.
Common Causes (4)
- Activation wire chafed or pinched against chassis ground.
- Coolant or water intrusion at the injector or DME connector.
- Internal injector short to body.
- DME internal fault (rare).
Diagnosis Steps (5)
- Read fault memory, checking for companion injector faults, blown fuses, or DME internal codes.
- Disconnect the line 4 injector, clear the code, and retest. Fault clears: injector is shorted. Fault returns: harness or DME.
- With both wire ends disconnected, measure insulation resistance to chassis ground. OL is good. Near 0 ohms is a direct short.
- Check both connectors for moisture or corrosion.
- Trace the harness from DME to the injector, inspecting every metal contact point for damaged insulation.
Resolution
Repair the chafed section, protect with loom, and re-route to prevent the same contact. For moisture-related faults, fix the leak source first and replace any wiring that has been contaminated. A shorted injector requires replacement with flow-value coding. Clear the code and rescan after a drive cycle to verify the repair.