P0456 Check Engine Light Reappears Monthly on 2015 Ram 2500 – What Should I Ask Dealership?

For more details on P0456: https://www.obd-codes.com/p0456

I now understand what P0456 means. The issue is that the dealership claims they’ve done everything possible, but the code keeps returning—what else could be causing this?

Does your 2015 Ram 2500 have a 5.7L engine? This affects available technical solutions.

Still waiting for a response—any updates on the diagnosis or next steps?

I know where the problem lies, but if you don’t provide accurate vehicle details, I can't offer a fix.

I’ve posted this three times and it’s not showing—my truck has a 6.5L Hemi engine!

Chrysler only offers 5.7L, 6.4L Hemi, or 6.7L Turbo Diesel engines for this model year.

I believe it's a 6.4L engine—confirmed by the VIN check.

Call Chrysler Customer Service. Report that your local dealer replaced multiple parts but the P0456 code persists. There are known Technical Service Bulletins (TSBs) for 5.7L engines that recommend reprogramming the Powertrain Control Module (PCM) to reduce sensitivity to P0456. For 6.4L models, no such TSB exists. If the dealer performed testing and found no fault but still replaced parts without your prior consent, that raises concerns about transparency. Did you pay out of pocket or are you under warranty? Either there’s a small evaporative leak the technician missed—or the PCM needs reprogramming to resolve the issue. Contact the dealership service manager or reach out directly to Chrysler Customer Service for further guidance.

I already have a Chrysler caseworker and filed a STAR case with the dealership. I’m scheduled for another appointment this morning. Chrysler advised them to inspect wiring—described as slightly corroded—and replace it. They said if the light returns, bring it back (35 miles one way). This makes me suspect the fix is temporary. They also promised a loaner vehicle and to keep it for a few days next time. I’m not confident this will resolve the issue long-term.

A thorough visual inspection, OBD-II scan tool, and smoke machine testing—especially with CO2 detection—are essential for identifying small evaporative leaks. These tools can detect leaks that are invisible to standard diagnostics. Many dealerships still use older equipment. Even a minor leak in the EVAP system can trigger P0456. I’ve seen cases where independent shops found issues dealers missed. If the system is functioning correctly, a PCM reflash may be needed.

I’m still under warranty, so I’m sticking with the dealership. I’ve read about smoke machine testing and will ask them to perform it during today’s visit—though I worry that as a woman, I might be dismissed or told I'm 'overreacting.'

Modern smoke machines use CO2 and detect leaks with color-changing spray foam. This technology is faster and more accurate than traditional methods. Many dealerships still rely on older tools, which may miss small EVAP system leaks. This could be critical for diagnosing P0456.

The service tech said they inspected the wiring—described as corroded—and replaced it. They told me if the light comes back, I need to return (35 miles one way). This suggests they’re not confident in the fix. They also promised a loaner and will keep the truck for a few days next time. It seems like no one truly knows what’s wrong—so I’ll just have to wait and see.

The check engine light will likely come back on again—I’m certain of it.

LOL—me too. How long until I decide to pursue a Lemon Law claim? This is becoming unbearable.

For your sake, I pray it doesn’t return. A 35-mile round trip is exhausting—especially when you’re driving through remote areas with no service. The P0456 code indicates a small leak—not a major circuit failure. To diagnose properly, use an OBD-II scanner to monitor the ESIM switch while pulling vacuum at the fuel filler neck and observe vacuum decay. If the system is healthy, a PCM reflash may be required. I know technicians who work on vehicles dealerships buy back from customers—then resell them. I wish you all the best. Please update if you find a resolution.

I’m a woman and my husband has dementia, so I manage everything—including driving through rugged terrain with no roadside support. Yesterday, I told the service tech that for four months every time the check engine light came on, the engine would take several seconds to engage (a 'chug chug' sound). Last week, I first saw a 'Service Electronic Braking System' warning—three separate issues. The technician said these are unrelated and didn’t know about any prior symptoms. It seems like there’s no communication between staff members. He told me I can drive safely, but I’m not convinced. We paid $51,000 cash for this truck—thinking it would be our last vehicle. Now, with temperatures at 118°F and on a mountain pass, what do I do if the light turns red? Whoever you are, Autojoe—I wish you were here. You sound like you have a heart. P.S.—I may have noticed that some letters after 'u' don’t type correctly here.

I hope they can resolve this. I’d strongly recommend seeking legal advice—this is a significant investment. My father had dementia for years before passing. You’re carrying a heavy load. I’m praying for you. Wishing I lived closer. I have all the diagnostic equipment available to me.