2018 Dodge Journey Check Engine Light Causes
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The 2018 Journey blends a 2.4L four-cylinder and 3.6L Pentastar V6 with Chrysler’s latest PCM software. A lit MIL means the ECU stored data explaining the fault. Use this guide to interpret the most common diagnostic trouble codes (DTCs), protect the catalysts, and confirm repairs before inspection.
- Applies to: 2018 Journey SE, SXT, GT AWD, Crossroad.
- Tools: OBD-II scan tool with Mode $06$, smoke machine, DVOM, fuel pressure gauge.
- Immediate warning: A flashing MIL indicates active misfire; reduce load immediately to prevent catalyst damage.
High-Priority 2018 Journey Codes
| Code | Subsystem | Common Cause | First Checks |
|---|---|---|---|
| P0300/P030x | Ignition/Fuel | Coils, plugs, injector imbalance, low compression | Review Mode $06$ misfire data, inspect plugs, swap coils, perform compression test. |
| P0420/P0430 | Catalyst | Misfire history, exhaust leaks, rich mixture | Check for misfires, compare upstream/downstream O2 waveforms, inspect manifold gaskets. |
| P2096/P2098 | Fuel Trim | Intake leaks, exhaust leaks, O2 sensor bias | Smoke-test intake and exhaust, verify fuel trims are within ±10%, inspect PCV hoses. |
| P0456/P0457 | EVAP | Loose gas cap, cracked vapor line, purge valve leak | Inspect cap seal, command purge closed, apply smoke via EVAP service port. |
| P06DD/P06DE | Oil Pump Control | Dual-stage oil pump stuck or wiring issue | Verify Mopar filter installation, measure mechanical oil pressure, inspect wiring near oil cooler. |
Diagnostic Workflow for the 2018 Journey
- Capture baseline data: Save all codes, freeze-frame information, fuel trims, and Mode $06$ results before clearing anything.
- Resolve misfires first: Replace worn plugs, swap coils, confirm injector pulse, and verify cylinder compression.
- Address fuel trim and catalyst codes: Repair vacuum or exhaust leaks, then monitor O2 sensors and trims on a road test.
- Check oil pump system: For P06DD/P06DE, ensure the correct filter is installed and confirm oil pressure with a mechanical gauge.
- Seal the EVAP system: Command purge closed, smoke-test the system, and replace damaged hoses or the ESIM assembly.
- Complete a validation drive: Clear codes, perform Chrysler’s drive cycle (idle, steady 45 mph, decel, highway cruise), and confirm monitors return to COMPLETE.
Driving Guidance During Diagnosis
- Do not tow or climb long grades while misfire or catalyst codes are active.
- Short trips are acceptable for EVAP-only faults, but repair before inspection deadlines.
- Monitor coolant and oil pressure gauges; shut down immediately if readings drift.
Preventive Maintenance Checklist
- Use MS-6395 compliant 5W-20 oil and Mopar MO-349 filter every 6,000 miles.
- Inspect intake manifold seals and PCV assemblies each oil change to stabilize fuel trims.
- Replace spark plugs at 100,000 miles (3.6L) or 60,000 miles (2.4L) and torque coils to spec.
- Check EVAP hoses near the charcoal canister for cracking in cold climates.
- Keep PCM and TCM software up to date; 2018 calibrations improve misfire sensitivity and stop/start logic.
Frequently Asked Questions
Can I clear the light by disconnecting the battery?
No. The PCM will rerun diagnostics and the MIL will return if the fault remains. Use a scan tool after repairs are complete.
Do P0420/P0430 always mean new converters?
Not necessarily. Fix misfires and fuel trim issues first, then perform a highway drive. Replace converters only if efficiency stays low after repairs.
How long until the light stays off after repairs?
Plan for 50 miles of mixed driving so misfire, catalyst, EVAP, and OBD monitors can confirm the repair.
Related Journey Resources
- 2014 Journey MIL guide for earlier model-year comparison.
- Dodge transmission troubleshooting for 62TE shift issues.
- Ignition diagnostics when misfires persist.