I'm pulling my hair out here! My 2022 RV with the 7.3 Godzilla engine (27k miles) threw a P0339 code along with hard starting and poor acceleration. Engine would barely turn over, then when it finally started it ran like garbage with warning lights everywhere. Could barely maintain 10mph before I had to shut it down.
Here's the weird part - I cleared the codes with my scanner and everything went back to normal! Engine starts fine now and runs perfectly. But I'm worried this is just the calm before the storm. What does P0339 actually mean on the Godzilla motor, and should I expect this problem to come back? Really hoping this might still be covered under warranty since the miles are so low.
P0339 on 7.3 Godzilla is intermittent crank sensor signal. Since clearing fixed it, monitor for recurrence. Likely sensor beginning to fail - should be warranty covered at 27K miles.
The P0339 code on your 2022 7.3 Godzilla indicates a crankshaft position sensor circuit fault (consult Ford service documentation for the exact definition for this engine). Given that your engine barely started, ran briefly with reduced power, then returned to normal after clearing codes, you're absolutely right to suspect a harness issue. The intermittent nature of your problem - where clearing codes temporarily restored normal operation - is a classic sign of a loose connection, damaged wire, or intermittent short in the crankshaft position sensor circuit. On the 7.3 Godzilla, this sensor is critical for timing and fuel injection, which explains why your RV lost acceleration power above 10 mph when the PCM detected the fault.
The fact that all symptoms disappeared after code clearing strongly suggests the sensor itself is likely fine, but there's an electrical connectivity problem somewhere between the sensor and the PCM. At only 27k miles, internal sensor failure would be unusual, making your harness theory very plausible.
On the 7.3 Godzilla engine, the crankshaft position sensor is mounted low on the engine block, making it vulnerable to road debris, moisture, and vibration damage to its wiring harness. The sensor connector and nearby wiring can suffer from corrosion, especially if you've driven through water or in high-moisture conditions. Vibration from road travel can also work connections loose over time.
Common failure points include the sensor connector itself, which can develop corrosion on the pins, and the section of harness that runs from the sensor up to the main engine harness. This area is exposed to heat cycles, vibration, and potential contact with moving parts. Additionally, rodents sometimes chew on accessible wiring, and the low-mounted sensor harness can be an easy target.
The intermittent nature suggests partial contact - the connection works sometimes but fails under certain conditions like vibration, temperature changes, or when moisture gets into a compromised connector. This explains why your engine started normally after clearing codes but may fail again when conditions change.
You'll need a basic set of tools including a socket set (verify actual bolt size in service manual), wire strippers, electrical contact cleaner, dielectric grease, and a multimeter with continuity testing capability. A flashlight or headlamp is essential since you'll be working in dark areas under the engine. Have some zip ties, electrical tape, and heat shrink tubing on hand in case you need to secure or repair any wiring.
Safety-wise, disconnect the battery negative terminal and ensure the engine is completely cool before starting work. The crankshaft position sensor area gets quite hot during operation. Work on level ground with the parking brake engaged, and consider using wheel chocks for added safety. Having a creeper or comfortable way to access the underside of the engine will make this job much easier.
If possible, have your OBD scanner ready to monitor the sensor signal in real-time while you manipulate connections. Some advanced scanners can show live crankshaft position sensor data, which helps identify exactly when the signal drops out during your testing.
Start by locating the crankshaft position sensor on the passenger side of the engine block, near the harmonic balancer. It's mounted with a single bolt and has a two-wire connector. First, visually inspect the connector for obvious damage, corrosion, or loose pins. Disconnect the connector and examine both the sensor side and harness side for green corrosion, bent pins, or moisture intrusion.
Clean the connector pins with electrical contact cleaner and a small wire brush if you find any corrosion. Check the connector's locking mechanism - it should click securely into place. Wiggle the connector while watching for any loose fit or damaged locking tabs. Apply a thin coat of dielectric grease to the pins before reconnecting.
Next, trace the sensor harness from the sensor toward the main engine harness, looking for damaged insulation, pinched wires, or areas where the harness might contact hot or moving components. Pay particular attention to where the harness transitions from the lower engine area up to the main harness - this is often where vibration damage occurs.
Use your multimeter to test continuity from the sensor connector pins all the way back to the PCM connector (refer to Ford wiring diagrams for specific pin numbers, wire colors, and PCM connector identification). The 7.3 Godzilla uses a reference signal and ground circuit (verify actual voltage specifications in Ford service documentation). You should see consistent continuity with no intermittent opens when you gently move or vibrate the harness. If you find an intermittent connection, isolate that section and repair with proper automotive-grade wire and heat shrink connections.
If your continuity testing shows good connections throughout the harness but you're still getting intermittent P0339 codes, the issue may be internal to the PCM or require specialized diagnostic equipment to isolate. Ford dealerships have access to advanced scan tools that can monitor the crankshaft position sensor's signal quality and timing, which goes beyond what typical OBD scanners can show.
Additionally, if you discover significant harness damage that requires extensive rewiring near the PCM connections, this work is best left to professionals. The PCM connectors are expensive to replace if damaged, and proper wire routing and securing in the engine bay requires knowledge of heat sources and moving components.
Should the problem persist after thorough connector and harness inspection, consider that the issue might be with the reluctor wheel on the crankshaft itself, though this would be extremely unusual on a 27k mile engine. This level of diagnosis requires professional equipment and expertise. Given that your symptoms were completely resolved by clearing codes, however, the odds strongly favor a simple connection issue that you can address yourself.
Help us improve this article by flagging technical issues or inaccuracies.
Was this guide helpful?
Try our free RV calculators and tools to help diagnose and plan your repairs.
Browse RV ToolsWeight calculator, electrical planner, propane estimator & more