2019 is the year that splits the Ram lineup: the all-new DT-body Ram 1500 (with the available eTorque mild-hybrid on the 3.6L Pentastar and 5.7L HEMI) launched alongside the carryover Ram 1500 Classic, while the heavy-duty trucks carried the 6.4L HEMI or 6.7L Cummins. A check engine light means different things across these — eTorque adds its own 48-volt codes, the HEMI leans on MDS misfires, and the Cummins brings DEF/DPF emissions codes. This guide covers what a 2019 Ram throws by drivetrain, how to read it, and when it’s safe to drive. For the full RAM history, see our Ram check engine light guide.
Which 2019 Ram Do You Have?
- 2019 Ram 1500 (DT, new body): 3.6L eTorque or 5.7L HEMI (with or without eTorque), ZF 8-speed. The eTorque belt-starter-generator and 48V battery add hybrid-specific codes.
- 2019 Ram 1500 Classic (old body): 3.6L Pentastar or 5.7L HEMI, no eTorque — diagnoses like a 2018-and-earlier 1500.
- 2019 Ram 2500/3500 HD: 6.4L HEMI gas or 6.7L Cummins diesel — the Cummins brings the DEF/SCR and DPF emissions family.
Reading Codes on a 2019 Ram
The 2019 trucks are push-button-start and generally don’t show codes on the odometer with the old key dance, so a basic OBD2 scanner is the practical route — and for the Cummins, a scanner with enhanced diesel data is worth it to read the DEF/DPF sub-codes. Pull the codes and look each up below. The free key-dance method (for older Dodges) is in our code-reading guide.
A flashing check engine light is an active misfire dumping raw fuel into the exhaust — it destroys the catalytic converter in minutes, and on a HEMI can signal a collapsed MDS lifter. Pull over and shut down. Start with the P0300 / P0301–P0308 misfire guides.
The Codes a 2019 Ram Actually Throws
| Code | What it means | Usual 2019 cause |
|---|---|---|
| P0300, P0301–P0308 | Random / cylinder-specific misfire | Plugs or coils; a collapsed MDS lifter on the 5.7L/6.4L HEMI |
| P0420 / P0430 | Catalyst efficiency below threshold | Aging converter or lazy O2 sensor (gas trucks) |
| P0456 | Very small EVAP leak | Hardened gas cap gasket, cracked vapor line (gas trucks) |
| P0128 | Coolant slow to reach operating temp | Stuck-open thermostat |
| P0700 | Transmission module stored a fault | ZF 8-speed (1500) or 68RFE/Aisin (HD) — read the TCM sub-code |
| U0100 / U0101 | Lost communication with a module | Weak battery, grounds, wiring |
| P204F / P20EE / P2463 | DEF/SCR & DPF (6.7L Cummins) | DEF quality/level, NOx sensors, soot-loaded DPF needing regen — diesel-aware diagnosis |
Each linked guide runs the diagnosis cheapest-cause-first. For the full picture across every Dodge code, see the master check engine light guide.
2019 Ram Signatures by Drivetrain
- eTorque (mild hybrid): the 48-volt belt-starter-generator system can set hybrid-specific codes and disable auto stop/start when the 48V battery or BSG has a fault. These aren’t a dead engine — but they need a scanner that reads the hybrid system, so don’t let the “check engine” scare you into engine teardown.
- 5.7L / 6.4L HEMI — MDS lifters: the deactivation lifters are the headline misfire cause; a single-cylinder misfire with a top-end tick that won’t follow a coil swap means stop and diagnose. The plugs & coils guide covers the coil-swap test, and the catalytic converter guide covers the P0420/P0430 that follow.
- 6.7L Cummins — DEF/DPF: the diesel’s emissions codes (P204F, P20EE family, P2463) point to DEF quality/level, NOx sensors, or a soot-loaded particulate filter needing a regen. Ignore them and the truck eventually de-rates into limp mode, so address diesel emissions codes promptly.
- Electrical/charging: a weak battery (or the second battery on diesels) drives U0100/U0101 and P0562 complaints — test the batteries and grounds before chasing modules.
Is It Safe to Keep Driving?
A steady light with no symptoms is usually an emissions fault — fine to finish the trip, but read the code within a few days.
A flashing light (active misfire), a Cummins DEF/DPF warning with a countdown or de-rate (address before it limp-modes), transmission limp mode, and a check engine light with an overheating gauge.
How to Reset the 2019 Ram Light
- Fix the cause first — clearing a live fault just brings the light back.
- Let it self-clear after the repair, or clear with a scanner and complete a drive cycle. Diesel emissions monitors and a completed regen can take longer.
- Avoid the battery-disconnect shortcut — on eTorque and diesel trucks especially, it wipes adaptations and resets readiness monitors, and you’ll fail a plug-in emissions test until they complete.
About the battery trick, honestly: the advice to disconnect the battery for fifteen minutes still gets passed around every Ram forum, so here is the straight version. Pulling the negative terminal usually does turn the light off — but it also resets every emissions readiness monitor the truck has completed (which reads as “not ready” at a plug-in emissions test until they re-run) and can cost you the ZF 8-speed’s learned shift feel while it re-adapts. And if the fault is still live, none of it matters: the light comes back as soon as the monitor re-runs and sees the fault, usually within a few drives. Basic code readers cost less than a tank of gas and let you read the fault first, then clear just the code — the monitors still have to re-run either way, but you’re not blind-wiping the whole truck to silence a lamp. If the truck is a keeper, that’s the better twenty dollars.
FAQ: 2019 Ram 1500 Check Engine Light
What is the difference between a 2019 Ram 1500 and a 2019 Ram 1500 Classic for check engine codes?
The 2019 Ram 1500 is the new DT body and can have the eTorque mild-hybrid system, which adds 48-volt hybrid-specific codes and stop/start faults. The 2019 Ram 1500 Classic is the carryover older body without eTorque, so it diagnoses like a 2018-and-earlier truck. Both share the common gas-engine codes, but only the new-body eTorque trucks throw the hybrid system codes.
How do I read check engine codes on a 2019 Ram?
Use a basic OBD2 scanner plugged into the port under the dash — the 2019 trucks generally do not display codes on the odometer with the old key dance. For the 6.7L Cummins, a scanner with enhanced diesel data is worth it to read the DEF and DPF sub-codes. Write each code down and look it up before buying parts.
What do the DEF and DPF codes mean on a 2019 Ram Cummins?
Codes like P204F, the P20EE family, and P2463 relate to the diesel’s emissions systems — DEF (diesel exhaust fluid) quality or level, NOx sensors, or a diesel particulate filter loaded with soot that needs a regeneration. They need diesel-aware diagnosis, and if ignored the truck will eventually de-rate into limp mode, so address them promptly.
Why is my 2019 Ram check engine light flashing?
A flashing check engine light means an active misfire is sending unburned fuel into the exhaust, where it can destroy the catalytic converter within minutes. Reduce throttle, pull over, and stop driving as soon as it is safe. On the 5.7L or 6.4L HEMI, a flashing light with a single-cylinder misfire and a top-end tick can also mean a collapsed MDS lifter, which can damage the camshaft.
Can eTorque cause a check engine light on a 2019 Ram?
Yes. The eTorque 48-volt belt-starter-generator and its battery can set hybrid-system codes and disable auto stop/start when something faults. These are not an engine failure, but they require a scanner that reads the hybrid system to diagnose. Have the 48-volt battery and BSG checked rather than assuming the worst about the engine.
Got a code from a scanner? Jump to its guide above. For the full Ram picture across all years and the diesel, see the model guide; a capable scan tool pays for itself on the first repair.