P042E on 2007-2024 RAM 2500 — Exhaust Gas Recirculation "A" Control Stuck Open
1 vehicles · 1 makes · $500-$1,800 repair
How to diagnose and fix P042E: most-reported vehicles
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RAM 2500 · 2007–2024
The EGR cooler routes hot exhaust through a coolant-jacketed heat exchanger before recirculating it into the intake. Heavy soot loading progressively plugs the cooler and EGR valve, first showing as slight off-idle hesitation and rising EGTs, then triggering EGR flow/performance codes and limp mode. Worse, a clogged, thermally stressed cooler can crack internally and leak coolant into the exhaust/intake stream, causing white smoke, coolant loss, and potential hydrolock or catastrophic engine damage. Cummins service intervals call for cleaning the EGR valve/cooler roughly every 67,500 miles (2007.5-2018) or 75,000 miles (2019+), which many owners never perform.
Common Symptoms
- Hesitation off idle
- Rising exhaust gas temperatures under load
- White exhaust smoke / sweet coolant smell
- Unexplained coolant loss
- Check engine light with EGR flow codes
- Reduced power / limp mode
How to Fix
Clean or replace the EGR cooler and valve. Genuine replacement cooler OEM PNs include 68048988AA (and related 4988885 / 4988884 / 68048991AA / 68444764AA for later trucks); an upgraded H-core cooler (e.g., BulletProof Diesel) resists cracking and clogging better than stock. Replace the EGR valve if the pintle is coked. Keep the DPF/regen system healthy, avoid excessive short-trip idling, and inspect/clean on Cummins' recommended interval to prevent the crack-and-coolant-loss failure mode.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Bullet Proof Diesel 6700121 H-Core EGR cooler
Confirm connection style and return-core terms.
- Bullet Proof Diesel 6700120 H-Core EGR cooler
Confirm existing cooler and connector style.
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Sources for this issue (3)
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P042E code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P042E mean?
P042E stands for "Exhaust Gas Recirculation "A" Control Stuck Open." P042E is a generic (SAE-standard) OBD-II powertrain code set when the powertrain control module determines the EGR "A" control valve is stuck in the open position — commanded flow does not drop to the expected level when the PCM commands the valve closed. With EGR flowing when it shouldn't, exhaust gas dilutes the intake charge at idle and low load. Drivers typically see a check engine light plus rough or unstable idle, hesitation, stalling on deceleration, and a failed emissions test.
What are the most common causes of P042E?
The most common causes of P042E are: EGR valve carboned up or stuck open by soot deposits, Failed EGR valve or its internal position sensor, Clogged or partially blocked EGR passages and cooler, Wiring, connector, or ground fault in the EGR valve control circuit, Vacuum leak or stuck vacuum solenoid on vacuum-actuated EGR systems, PCM software/calibration issue or, rarely, a failed PCM driver. The specific cause varies by vehicle.
How much does it cost to fix P042E?
Repair costs for P042E range from $500 to $1,800, depending on the vehicle and root cause.
Which vehicles are affected by P042E?
Au7o has documented P042E across 1 vehicle models from 1 manufacturers: RAM.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.