I currently have no problem but I do have a phenomenon that perhaps one of you wizards can explain to me.

Truck is a 2004 F150 Lariat with a remanufactured 5.4L, 3 valve engine installed in February of 2018. The truck has always thrown an occasional fault code PO330 (Bank 2 knock sensor fault). It threw this code whenever driven aggressively. It was easily reset and with normal driving did not return unless excessive throttle or passing gear was used. It was not that much of an irritant and replacing the sensor was on my Do Someday When Bored List.

A couple of days ago, I preemptively replaced my FPDM. Since then, the PO330 code has not reappeared even though I tried to make it do so. I drove hard, fast and basically abused the engine trying to set that code. No dice. I checked for pending codes and got nothing. Apparently replacing the FPDM also fixed whatever was annoying the system.

My question is Why?. According to the code list, there was no actual lean/knock condition, only a bad sensor.

 

Bump for the Wizards.

 

Are you sure it wasn't actually pinging? If the fuel pump wasn't putting out enough juice under load maybe it was pinging that would make more sense here because that would only show up under high loads or acceleration.

 

May have been but it was not audible. The code PO330 is also for a sensor failure not an actual engine knock (ping) or a lean condition or misfire. The engine did not stumble on acceleration.

Thanks for the input but the mystery remains to me.

 

Do a physical check of the wires/sensor. Mine was intermittent as well. Found one wire shredded near the firewall.

 

In absence of that always preferable 'first hand knowledge' (which I am in this case) --- but I can relate a similar situation that might be helpful.

I replaced my A/C compressor at the time of my timing job. As 'Murphy' dictates, the new A/C compressor was horribly noisy / whinney. With Torque Pro I could see a HUGE difference in the voltage level output by the knock sensor on Bank 1. I was shocked to see the difference when I replaced the 'repacement' compressor. Surprising how sensitive they are to ambient noises.

Having said that, I would point out that reported "Circuit" problems are usually related to Shorts or opens --OR-- over / under voltage readings or performance beyond expected ranges. Exploring that theory - are there any excessive noisy components under your hood that get louder under acceleration - high RPM's that could drive the knock sensor output out of normal range?

 

F150Torqued:

Good thoughtful response. The engine is very quiet. I even tried to drive it in a manner that was sure to set the code in the past. Ecobuilder's comment on wiring is also interesting. When I plugged into the new FPDM, I didn't like the feel of the plug-jack mating so I added a TyWrap to positively hold the plug in place. Maybe that helped.