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2013 Ford F-150 5.0L Misfire: P0390 & P0394 Codes Return After Engine Wash

Model: 2013 Ford F 150 5.0 Fault Code: P0390 Posted: 2015-05-05 11:48

A 2013 Ford F-150 5.0L engine was brought in for a misfire issue. The owner replaced cylinder 6 spark plug and coil, but the problem persisted. A compression test revealed low compression in cylinder 6, leading to replacement of the lower head assembly. After this repair, the engine started running smoothly with no symptoms for two days. However, after washing the vehicle, the same misfire codes P0390 and P0394 reappeared. The owner has since replaced the PCM and the secondary timing chain tensioner. All wiring and connectors were inspected and found to be in good condition. The issue appears intermittent—only occurring after driving and subsequent ignition cycling (e.g., turning off the engine briefly, like when leaving a store). Despite extensive troubleshooting, the codes return consistently post-wash. Any insights into potential root causes related to camshaft sensors or wiring integrity would be greatly appreciated.

Related fault codes
P0390P0394
Comments (2)
Anonymous 2015-05-05 14:27

Something doesn't add up for a 2013 Ford F-150—cylinder head, PCM, and timing chain tensioner all replaced. Why wasn't this covered under warranty? The codes point to a camshaft position sensor issue with intermittent faults. The fact that symptoms reappear after an engine wash suggests possible wiring contamination or moisture ingress in the harness.

Anonymous 2015-05-05 14:36

This should be covered under warranty. I've disconnected and inspected the entire wiring harness—resistance tests were normal, and no visible damage was found. The codes only appear after driving and then cycling the ignition on and off, which mimics a scenario like leaving a store. This behavior strongly suggests an intermittent electrical fault, possibly related to sensor signal degradation or environmental exposure.