2002 Ford F150 5.4L P0340 Code: CMP Sensor Voltage Issue and Misfire at 55-80 MPH
I've been experiencing a persistent P0340 diagnostic trouble code on my 2002 Ford F150 with the 5.4L V8 engine. The vehicle is equipped with a two-wire Cam Position (CMP) sensor, and continuity to ground has been confirmed as good. Using a voltmeter, I'm measuring only 0.1 volts from the sensor output — significantly below expected levels. The sensor was replaced three times previously using an OEM Ford ORM CMP sensor; the highest voltage recorded during testing was 0.5V at approximately 2,500 RPMs. The vehicle exhibits a noticeable misfire or lurching sensation specifically when cruising between 55 and 80 mph on flat roads. This behavior does not occur during acceleration or coasting. The issue is consistent only under steady-state highway conditions. Based on manufacturer specifications, the CMP sensor should produce higher output voltages at engine operating temperatures and RPMs typical of cruise speeds. I've also confirmed that my crankshaft position sensor outputs a stable 2V at idle — using the same two-wire induction-type design. I'm wondering if there could be an issue with sensor calibration, wiring resistance, or a faulty ground connection despite continuity tests passing. Any insights into troubleshooting this P0340 code in a 2002 F150 would be greatly appreciated.
Check the voltage drop from the sensor's ground terminal to the engine block. It should read zero volts under normal conditions. A significant voltage drop indicates a poor ground connection. Additionally, verify whether there is a reference voltage supplied by the Powertrain Control Module (PCM) to the CMP sensor — this is essential for proper signal generation and accurate readings.