Honda 3.5L Rattling, Growling, Thumping, Vibration
Documenting a fairly detailed diagnostic process for a 2018 Honda Pilot with a 3.5L engine. The issues include a check engine light triggered by O2 sensor faults, a noise related to exhaust or heat shield, and a suspected issue with the high-pressure fuel pump.
Oxygen sensor heater circuit malfunction code for Bank 2, Sensor 2. Visual inspection showed that the sensor had likely been impacted by debris, and the heater circuit wasn't functioning correctly (voltage dropping to 5V instead of staying within expected values). Active tests showed the heater circuit wasn't activating properly, confirming a defective sensor.
The noise is a mixture of exhaust and heat shield sounds, which led to further investigation of the high-pressure fuel system. Use of an accelerometer and fuel line vibration testing pinpointed the source of the noise to the high-pressure fuel pump, which was vibrating in sync with engine RPM. The noise was being transmitted through the fuel line to the tank.
After analyzing the vibrations and sounds with an oscilloscope, it was identified that the high-pressure fuel pump was causing the issue. The high-pressure fuel pump was driving the fuel line vibration frequency, and a detailed analysis using the scope confirmed the vibrations were consistent with the fuel pump's operating frequency. It is the only device that could have 3 percussions for every 720° of crankshaft rotation.