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P0456, P0440, and P0004 OBD2 Codes on 2006 Dodge Ram 2500: EVAP System & Fuel Control Issues

Model: 2006 Dodge Ram 2500 Fault Code: P0004 Posted: 2012-09-01 19:30

Hi everyone, I recently purchased a used 2006 Dodge Ram 2500 with a 5.7L Hemi V8 gasoline engine from a dealership about a month ago. During the test drive, the check engine light was on, so I asked the dealer to perform an OBD2 scan. They claimed they couldn't detect any fault codes and cleared them — which didn’t make sense to me at the time. After clearing the codes, the check engine light turned off during my first few drives. About a week later, the gas cap warning light (located on the odometer panel) came on, followed by the check engine light again. I tried removing and reattaching the gas cap, but that didn’t resolve the issue. Using my own OBD2 scanner, I detected three fault codes: P0456, P0440, and P0004. Interestingly, the gas cap warning light has since disappeared on its own, though the check engine light remains illuminated. This raises a concern — was it possible that the dealership’s scan tool failed to detect these codes? If so, how serious is this oversight? I understand that P0456 and P0440 are related to the Evaporative Emission (EVAP) system, but I have no prior experience with this model or engine. Could anyone provide insight into what these codes mean, especially P0004? Are they common in 2006 Dodge Ram 2500s? And if so, are they indicative of a major issue that could affect reliability or safety? Thanks for any advice — I’m trying to determine whether this vehicle is worth keeping or if I should consider trading it in or negotiating significant repairs and credits.

Related fault codes

P0004P0440P0456

Comments (5)

Anonymous 2012-09-02 13:21

The P0004 code indicates a 'Fuel Volume Regulator Control Circuit High' issue. This typically points to a problem with the fuel volume regulator sensor or its wiring. I recommend checking for loose connections, corrosion, or damage in the sensor circuit. Also, ensure your OBD2 scanner is properly calibrated and supports the 2006 Dodge Ram's diagnostic protocol. Regarding the dealership — was this an authorized Dodge dealer? If not, their ability to read codes may be limited. Many non-authorized dealers use outdated scan tools that don’t support newer generic DTCs. A GM-trained technician might have used a basic $10 scanner, which often fails on specific vehicle systems like the Ram's fuel control module. Also, verify if the truck has any performance modifications (e.g., chips or lift kits). The 2006 Ram is typically stock, especially in work-truck configurations. A former oilfield use history could indicate wear and tear on emissions components.

Anonymous 2012-09-02 17:43

Thanks for the clarification — I’ve confirmed that the truck has no performance chips, lift kits, or modifications. It was previously used as a work truck in the oil patch, which may have exposed it to harsh conditions and potential EVAP system wear. I’m now planning to take the vehicle to Napa and another auto shop for a second scan to compare results with my current reader. If the codes persist, I’ll consider returning the truck or negotiating a significant repair allowance. Honestly, I feel misled by the dealer’s claim of no issues — especially since they didn’t detect these common OBD2 faults. I’m also considering whether to trade it in or keep it if repairs are manageable. This experience has made me more cautious about buying used trucks from non-authorized dealers.

Anonymous 2012-09-02 18:01

EVAP system issues like P0456 and P0440 typically require a smoke machine test to properly diagnose — simply clearing codes won’t fix the root cause. A basic scan may show generic DTCs, but without actual leak detection, it’s hard to confirm if the EVAP system is truly faulty. Clearing codes and returning the vehicle without addressing the issue should be viewed as a red flag for transparency and technical competence.

Anonymous 2012-09-03 05:44

P0004 = Fuel Volume Regulator Control Circuit High. This code suggests an electrical or sensor fault in the fuel volume regulator system, which controls fuel pressure. Common causes include faulty wiring, a damaged sensor, or poor grounding. For a 2006 Dodge Ram 2500, this could lead to inefficient fuel delivery and potential engine performance issues. Always inspect the harness and connections near the fuel rail or intake manifold when troubleshooting.

Anonymous 2012-09-03 07:55

The 2006 Dodge Ram may have transitioned from DRB3 to a newer STARSCAN system, but all diagnostic trouble codes (DTCs) are generic and readable with basic OBD2 scanners — even affordable $10 tools. That said, the P0004 code is particularly concerning and likely points to an ESIM (Electronic Sensor Interface Module) switch issue. I’d strongly recommend taking it back to a certified Dodge dealer for a proper diagnosis, but remain cautious about buying vehicles with oilfield histories due to potential mechanical wear on emissions components.