P0402 on Jeep: How to Diagnose & Fix
Exhaust Gas Recirculation Flow Excessive
1 Jeep model · 1 documented issue · 1 critical · $1,200-$3,000 repair
P0402 on Jeep by model: symptoms, diagnosis and fix
The exhaust gas recirculation cooler on the 3.0L EcoDiesel can crack internally, allowing coolant to weep into the exhaust gas stream. Because the coolant boils off into the intake and exhaust, the truck loses coolant steadily with no puddle on the ground; owners report topping off repeatedly while dealers chase a phantom external leak. The coolant combines with soot to varnish the intake ports and EGR valve, causing driveability faults and NOx-related emissions codes. Some cases mimic a head gasket failure with combustion gas detected in the coolant.
Common Symptoms
- Coolant level dropping with no visible external leak
- White or sweet-smelling exhaust
- Overheating or fluctuating temperature gauge
- Check engine light with EGR flow or NOx faults
- Sooty/oily residue in the intake
How to Fix
Have the cooling system pressure- and block-tested; a chemical combustion-gas test on the coolant plus a borescope of the intake confirms EGR cooler leakage rather than a head gasket. The repair is EGR cooler replacement (frequently with the EGR valve and an intake cleaning) and a coolant system flush. Owners report replacements as early as 30k-40k miles under the emissions/powertrain warranty, so document coolant top-offs early.
Sources for this issue (3)
P0402 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 P0402 mean on a Jeep?
P0402 stands for "Exhaust Gas Recirculation Flow Excessive." P0402 means the Exhaust Gas Recirculation (EGR) system is flowing too much exhaust back into the intake. The EGR system intentionally routes a small amount of inert exhaust gas into the engine to lower combustion temperatures and reduce nitrogen-oxide emissions, but the flow must be metered precisely. When the PCM determines the flow is excessive — often because the EGR valve is stuck open or letting gas through when it shouldn't — it sets this code. Too much EGR can cause rough idle, stalling, hesitation, and a check engine light. On Jeep it is documented across 1 model: Gladiator.
What are the most common causes of P0402?
The most common causes of P0402 are: EGR valve stuck open or not closing fully, Failed or sticking EGR valve diaphragm/solenoid, Carbon buildup holding the EGR valve open, Faulty EGR position or differential pressure (DPFE) sensor, Leaking EGR valve gasket or pintle seat, Vacuum control or solenoid fault commanding EGR open, Wiring or connector problems in the EGR control circuit. The specific cause varies by vehicle.
How much does it cost to fix P0402 on a Jeep?
Published repair estimates on Jeep range from $1,200 to $3,000 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0402 on a different make?
View P0402 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.