P0175 on the 2018 Ram 1500: Higher-Mileage HEMI Diagnosis
The 2018 Ram 1500 — the last year of the fourth-generation (DS) body style — is most commonly equipped with the 5.7L HEMI V8 (395 hp) or the 3.6L Pentastar V6 (305 hp). At 6-8 years old with potentially 70,000-130,000 miles, these engines are squarely in the zone where fuel system components reach end-of-life, making P0175 increasingly likely.
The HEMI V8 has a true Bank 2 on the passenger side (cylinders 2, 4, 6, 8), and P0175 specifically points to excess fuel delivery on those cylinders. At this mileage, multiple factors may be contributing simultaneously.
Symptoms at Higher Mileage
- Check engine light — may be intermittent at first, then steady
- Fuel economy down significantly — HEMI owners may see 12-14 MPG city instead of 15-17
- Pronounced rough idle
- Heavy fuel smell from the exhaust
- Visible black smoke under hard acceleration
- Noticeable power loss, especially when loaded or towing
- MDS (Multi-Displacement System) may not engage properly
- Spark plugs fouling prematurely
Why Your Higher-Mileage 2018 Ram Is Running Rich
1. Worn MAF Sensor — High Likelihood
After 70,000+ miles of exposure to dust, dirt, and PCV oil vapors — common in truck duty cycles — the MAF sensor is likely degraded. The 2018 Ram's intake design pulls air through a relatively exposed air box that's often subjected to road dust, construction debris, and off-road conditions. A worn MAF that underreads by 10-15% causes a substantial rich condition on the large-displacement HEMI. Replacement is the recommended fix at this mileage rather than cleaning.
2. Failed O2 Sensor — High Likelihood
Oxygen sensors typically last 80,000-120,000 miles, and your 2018 Ram is in the replacement window. The upstream O2 sensor on Bank 2 has endured years of HEMI exhaust heat — among the highest in the truck segment. A sensor that's slow to respond or stuck at a particular voltage causes continuous fuel trim miscalculation. Replacing both upstream sensors simultaneously is cost-effective since the second sensor is likely close to failure as well.
3. Leaking Fuel Injectors — Medium Likelihood
HEMI injectors at 70,000+ miles have fired hundreds of millions of times. Seal wear, carbon deposits, and injector coking cause some injectors to drip or over-deliver. On Bank 2 (cylinders 2, 4, 6, 8), even one leaking injector enriches that bank's exhaust enough to trigger P0175. An injector balance test using a bidirectional scan tool identifies the problem injector.
4. Catalytic Converter Inefficiency — Low Likelihood
Years of running rich (possibly from a gradually failing sensor that only recently crossed the P0175 threshold) may have damaged the Bank 2 catalytic converter. An overloaded converter creates back pressure that affects O2 sensor readings and fuel trim calculations. Checking the downstream O2 sensor voltage pattern reveals converter health — it should hold relatively steady near 0.7V during normal operation.
Diagnostic Process
- Scan for all codes — look for companion codes like P0172 (Bank 1 rich) or misfire codes
- Check spark plug condition on Bank 2 — black, sooty plugs confirm rich running
- Compare Bank 1 vs Bank 2 fuel trims at idle and 2,000 RPM
- Test MAF sensor at idle and under load
- Monitor O2 sensor response on both banks — compare for degradation
- Run fuel pressure test at the rail
- Check catalytic converter efficiency via downstream O2
Repair Costs
- MAF sensor: $80–$200
- O2 sensor (each): $100–$250
- Fuel injector (each): $60–$160
- Catalytic converter: $400–$1,200
- Spark plugs (set of 16 for HEMI): $100–$200
DIY-Friendly Repairs
The 2018 Ram 1500 is one of the most DIY-accessible trucks. The engine bay is spacious, parts are affordable, and repair procedures are well-documented. MAF sensor replacement takes 5 minutes. Spark plugs on the HEMI require a 5/8" plug socket — the plug tubes are deep but accessible. O2 sensors may require penetrating oil due to years of heat exposure. Injector replacement requires fuel rail removal but is manageable for experienced DIYers.