P0175 Code: Honda Accord (2018-2023) - Causes, Symptoms & Fixes

Diagnostic guide: P0175 on 2018–2023 Honda Accord

Important data note

• Owner complaints for this exact make/model/year/issue: No NHTSA complaints found.
• Official recalls in NHTSA database: No recalls found.
• No recalls found in NHTSA database (as required by the data rules).
• These data points are limited to what’s in the snippet you provided. No complaint counts or recall entries do not imply the issue can’t occur in the real world; they merely reflect the given data snapshot. The guide below uses general automotive knowledge and typical P0175 behavior on Honda Accords, along with the typical symptoms and diagnostic flow you’d follow in the shop.

CODE MEANING AND SEVERITY

• Code: P0175
• Description (OBD-II generic): System Too Rich (Bank 2)
• On many modern inline-4 Hondas (like many Accord engines), “Bank 2” terminology isn’t as relevant because there is typically a single cylinder bank. When P0175 appears on an Accord, it generally indicates that the engine control module (ECM/PCM) is detecting that the fuel trim on Bank 2 is richer than expected (too much fuel relative to the measured air). This results in higher than target air-fuel ratio (AFR) and can trigger the MIL (check engine light).
• Severity and drivability: Moderate. A rich condition can cause rough running, emissions concerns, and reduced fuel economy. If left unresolved, it can lead to catalytic converter overheating or failure, misfires, or catalyst damage in some cases.
• Likelihood you’ll see related codes: Often P0175 is accompanied by P0171/P0174 (lean conditions on Bank 1/Bank 2) if the trims swing between banks, or by sensor-related codes (P013x, P014x) if sensors are involved. Always check for multiple codes and freeze-frame data.

COMMON CAUSES ON THE 2018–2023 HONDA ACCORD

Note: While the same list applies broadly, Hondas (especially with turbocharged 1.5L/2.0L engines and direct injection) have some model-specific patterns.

Likely causes

• Vacuum leaks or PCV system issues on the intake side (including around the PCV valve and hoses). A leak can cause erratic fuel trims and a compensating rich condition on one bank.
• Faulty or dirty mass air flow (MAF) sensor. A MAF that reads high or fluctuates can cause the PCM to enrich fuel to compensate for perceived extra air.
• Faulty or slow upstream oxygen sensor (O2 sensor) on Bank 2. The sensor may report rich or slow response, causing the PCM to over-fuel.
• Fuel delivery issues
  • Excessively high fuel pressure (faulty fuel pressure regulator or pump issue in some configurations) can cause over-fueling.
  • Injectors leaking or sticking open on Bank 2, causing excess fuel on that bank.
• Direct injection-specific carbon buildup and port injection balance (for engines with direct injection). Carbon buildup can disrupt air-fuel delivery and sensor readings, leading to abnormal fueling.
• Exhaust or intake leaks that alter sensor readings (before/after the O2 sensors) can skew fuel trims.
• Faulty or degraded sensor wiring or PCM/ECU communication issues (less common but possible).
• Fuel quality issues or incorrect octane/fuel additives (less common but possible in some cases).

Less common / secondary causes

• Stuck open or failing intake manifold vacuum gasket on Bank 2 side (especially on engines with split banks).
• Faulty or contaminated downstream exhaust components altering cat/pre-cat readings (less common as primary cause but possible with persistent trim issues).
• Software/ calibration issues in the ECM/PCM (rare, but require factory software update if applicable).

SYMPTOMS YOU MIGHT NOTICE

• Check Engine Light (CEL) or MIL illuminated.
• Rough idle or hesitation, especially at idle or low load.
• Noticeable increase in fuel consumption (lower MPG).
• Strong fuel odor from exhaust or around the tailpipe (fuel-rich exhaust can be noticeable).
• Possible exhaust smoke or a dark exhaust plume under certain driving conditions.
• Possible misfire symptoms if the rich condition triggers cylinder misfires.
• Possible improvement after engine warms up (trim behavior can vary with temperature and load).

DIAGNOSTIC STEPS (step-by-step flow)

Note: Always work safely and with the engine cool when performing inspections that involve fuel or cooling systems. Use a scan tool capable of live data, fuel trims, and bank-specific readings.

A. Confirm and characterize

• Scan for codes: Confirm P0175 is present. Note any related codes (P0171, P0174, P013x, P014x, P0138, P0139, etc.).
• Retrieve freeze-frame data: Look at long-term fuel trim (LTFT) and short-term fuel trim (STFT) for Bank 2. If LTFT is +15% to +30% or higher, you’re in a confirmed rich condition for Bank 2. Compare Bank 1 trims if available.
• Check engine coolant temperature (ECT) and air temperature values for anomalies, as trim calculations depend on accurate air-temperature measurements.

B. Inspect primary suspects (mechanical and sensor health)

• Vacuum leaks and PCV system
  • Visually inspect intake plumbing, hoses, and PCV valve for cracks, disconnections, or deteriorated hoses.
  • Perform a smoke test if available to reveal small leaks in intake manifolds, gaskets, or vacuum lines.
• MAF sensor
  • Inspect for dirt/debris. Clean with a specialized MAF cleaner if you suspect contamination (follow product instructions).
  • Check for proper air intake restrictions (clogged air filter, collapsed intake tube).
  • After cleaning, clear codes and drive to see if trims normalize.
• O2 sensors (Bank 2 upstream O2 sensor)
  • Use live data to compare the Bank 1 vs Bank 2 O2 sensors’ readings and switching behavior. A Bank 2 sensor that lags or reads abnormally rich can drive compensation in the PCM.
  • Inspect wiring and connectors for damage or corrosion.
• Fuel system
  • Check fuel pressure with a fuel pressure gauge and compare to factory specs for the engine variant (turbo 1.5L or 2.0L). Verify regulator/pump functionality.
  • If accessible, perform a fuel injector balance test for Bank 2 injectors (listening with a stethoscope or using a noid light with a fuel pressure test rail) to detect leaks or sticking injectors.
  • Inspect fuel filter (if applicable) and overall fuel quality.
• Direct injection carbon buildup (especially for 2.0T or 1.5T engines)
  • Consider potential carbon buildup on intake valves affecting mixture and sensor readings. If symptoms align (rough idle, misfires, poor acceleration), a carbon-cleaning service may be considered.
• Exhaust leaks
  • Check for leaks before the downstream O2 sensors or at the exhaust manifold that could alter EGT/O2 readings.
• Electrical and connectors
  • Inspect harnesses to Bank 2 sensors and injectors for chafed wires or loose connectors.
  • Check PCM power and ground circuits for consistency.

C. Targeted tests if issues remain

• Swap/replace suspect sensor (start with easier/cheaper items):
  • Bank 2 upstream O2 sensor
  • MAF sensor (if not recently serviced)
  • PCV valve (and associated hoses)
• Clean or replace injectors if a balance test indicates misbehavior on Bank 2 injectors.
• Re-measure fuel pressure after any pump/filter changes.
• If all external causes are ruled out, consider engine management/ECU reprogramming or more extensive diagnostics with manufacturer guidance.

D. Do not forget basic maintenance checks

• Air filter: replaced if dirty.
• Spark plugs: check condition and gaps; replace if worn—misfires can skew fuel trim readings.
• Engine oil and necessary fluids: ensure proper levels; some faults can be aggravated by poor lubrication or sensor grounding.

RELATED CODES

• P0171: System Too Lean (Bank 1)
• P0174: System Too Lean (Bank 2)
• Other fuel trim related traces may appear (P013x/P014x family) depending on sensors and bank behavior.
• Note: If multiple fuel-trim codes are present, approach diagnosis as a system-wide fueling issue rather than a single sensor problem. Use live data to compare trims between banks and correlate with sensor readings.

REPAIR OPTIONS AND COSTS (2025 PRICES)

Prices vary by region, labor rate, and parts quality. The ranges below reflect typical U.S. shop pricing as of 2025 and are intended as ballpark figures.

A. Quick fixes / low-cost fixes

• Clean MAF sensor or replace if needed
  • Parts: $20–$130 (clean) or $70–$180 (new)
  • Labor: $40–$120
  • Estimated total: $60–$300
• Vacuum leaks and PCV valve service
  • PCV valve replacement: Part $10–$25; Labor $40–$120
  • Vacuum hose replacement: Parts $5–$50; Labor $40–$150
  • Estimated total: $60–$350
• O2 sensor (Bank 2 upstream) inspection; replacement if faulty
  • Parts: $60–$230
  • Labor: $60–$140
  • Estimated total: $120–$370

B. Moderate fixes

• Fuel pressure regulation / fuel system service
  • Fuel pressure regulator (or related fuel rail service): Parts $60–$200; Labor $100–$250
  • Fuel pump replacement (if needed): Parts $150–$500; Labor $200–$600
  • Estimated total: $300–$1300
• Injector servicing (Bank 2 injectors)
  • Cleaning service or replacement (if sticking/leaking): Parts $30–$100 per injector (if replacing 1–2 injectors, or a set $120–$400 total)
  • Labor $150–$350
  • Estimated total: $300–$900 (single bank focus) or $600–$1600 for full bank/whole-set service
• Intake manifold gasket or major vacuum leak repair
  • Parts $60–$300
  • Labor $200–$700
  • Estimated total: $260–$1000

C. Major / advanced repairs

• Direct-valve carbon cleaning (intake-valve cleaning, walnut blasting, etc.)
  • Parts: $0–$60 (chemicals) or up to $60 for specialized cleaning agents
  • Labor: $500–$1100
  • Estimated total: $500–$1100 (for modest cleaning); more if extensive
• Intake manifold gasket replacement or major manifold work
  • Parts: $100–$500
  • Labor: $300–$800
  • Estimated total: $400–$1300
• PCM/ECU/software reflash or programming (rare; only under manufacturer guidance)
  • Parts/Labor: $100–$300 in many shops; plus any dealership programming fees
  • Estimated total: $100–$500

D. When to expect higher costs

• If multiple components are implicated (e.g., MAF, O2 sensor, injectors, and a fuel-pressure system) or if there is significant carbon buildup, total repair cost can approach the top of the ranges above.
• If a dealer-level diagnostic is required and special tooling is needed, expect higher labor rates.

Note: These price ranges assume typical U.S. shop rates and generic replacement parts. Local taxes, shop certifications, and vehicle access constraints can affect total cost. Always get multiple estimates and ask for an itemized quote.

DIY vs PROFESSIONAL

• DIY-friendly options (lower-risk, low-cost)
  • Cleaning MAF sensor (with proper aerosol cleaner) if you’re comfortable handling sensor cleaning and clearing codes afterward.
  • Inspecting vacuum hoses, PCV valve, air filter, and basic wiring visually.
  • Checking and logging live fuel-trim data via a capable OBD-II scanner to observe trim behavior.
  • Replacing simple components like upstream O2 sensor (if you’re comfortable with basic electrical work) with proper torque specs.
• Professional tasks (recommended for accuracy and safety)
  • Fuel pressure testing and diagnosis (requires gauge and proper safety).
  • Injector balance testing and cleaning/replacement.
  • Smoke testing for vacuum leaks (requires specialized equipment).
  • Intake carbon buildup remediation for direct-injection engines (often requires walnut blasting or specialized cleaners and expertise).
  • PCM/ECU software updates (requires dealer tooling and correct calibration).
• Safety and warranty considerations
  • Working with the fuel system and ignition system requires caution to avoid fire hazards.
  • If your car is under warranty or you’re in a covered maintenance program, consult the manufacturer guidelines.

PREVENTION

• Regular maintenance on schedule
  • Replace air filter on time to prevent MAF contamination or restricted airflow.
  • Maintain PCV system: replace PCV valve as recommended by Honda service intervals.
  • Use quality fuel and appropriate octane as specified for your engine variant.
  • Avoid fuel with high ethanol content if not recommended; use stabilizers if you drive infrequently.
• Keep intake system clean
  • For direct-injection engines, consider periodic fuel-system cleaners that are compatible with direct-injection systems (per Honda guidelines) to reduce carbon buildup; consult your owner’s manual or dealer guidance.
• Monitor fuel trim readings
  • If you notice fuel economy dropping or the MIL coming on intermittently, address fuel trim anomalies promptly rather than waiting for a more serious symptom.
• Prompt attention to rough idle or misfires
  • Misfires can accelerate catalyst damage and increase emissions, making it important to diagnose early.
• Regular sensor checks
  • Ensure MAF and O2 sensors are in good condition; replace failing sensors before they drive larger issues.

Bottom line

• P0175 on a 2018–2023 Honda Accord points to a richer-than-expected fuel condition on Bank 2. The most common root causes tend to be vacuum/PCV issues, MAF sensor behavior, O2 sensor readings, or actual fuel delivery anomalies (pressure or injectors). Start with quick sensor/air-path checks and move toward fuel-system testing if the problem persists. Because of modern direct-injection engines, carbon buildup and injector health can also play a significant role.
• Given the data snapshot provided (no complaints, no recalls), this guide emphasizes diagnosis based on standard automotive practice and Honda-specific considerations, while remaining transparent about data limitations.

If you want, I can tailor a diagnostic flowchart for your exact Accord engine variant (1.5L turbo vs 2.0L turbo) and provide a more precise set of tests and part-cost estimates based on your location.