P0468 is an evaporative emissions (EVAP) system code that can be confusing when you first see it on your scan tool. It points to a problem with the EVAP purge flow sensor circuit, specifically a high signal. In plain language, your car’s computer is seeing an electrical value from the EVAP sensor that doesn’t make sense. While this code usually won’t leave you stranded, it can cause drivability issues, fuel odor, and a failed emissions test. Understanding what P0468 means, how it behaves, and how to fix it will save you time, money, and frustration.
What Does P0468 Mean?
P0468 is defined as “EVAP Purge Flow Sensor Circuit High Input” (or similar wording depending on the manufacturer). The EVAP system captures fuel vapors from the gas tank and routes them to the engine to be burned instead of vented to the atmosphere. The purge flow sensor (or EVAP pressure/flow sensor on some cars) tells the ECU how much vapor is flowing.
When the ECU sees a voltage signal from this sensor that’s higher than the expected range, it flags P0468. This can be caused by wiring faults, a failing sensor, or sometimes a problem inside the ECU itself. The code is electrical in nature, not just a simple leak like many other EVAP codes.
Quick Reference
- Code: P0468
- Meaning: EVAP purge flow sensor circuit high input
- System: EVAP (evaporative emissions control)
- Severity: Low to moderate (usually not an immediate breakdown risk)
- Typical fixes: Wiring repair, connector cleaning, purge flow/pressure sensor replacement
Real-World Example / Field Notes
In the shop, I usually see P0468 on vehicles that have had previous EVAP work or have lived in rust-prone or very hot climates. One example: a compact SUV came in with a check engine light, slight fuel smell, and code P0468 stored. The owner had already replaced the gas cap and purge valve with cheap aftermarket parts. After testing, the actual problem was a corroded ground splice and a partially broken wire near the EVAP sensor harness, causing the sensor signal to float high. A simple wiring repair and a new OEM-style connector fixed the issue permanently.
Symptoms of P0468
- Check engine light (MIL) on: The most common and sometimes only symptom.
- Failed emissions test: OBD readiness monitors may not set, or the inspector sees the stored code.
- Fuel odor: You may notice a mild fuel smell near the rear of the vehicle or around the filler neck.
- Rough idle or stumble: Incorrect EVAP purging can slightly upset the air-fuel mixture at idle.
- Hard start after refueling: Excessive or poorly timed vapor purging can make hot restarts harder.
- Reduced fuel economy: The ECU may adjust fuel trims to compensate for incorrect EVAP data.
- Other EVAP codes present: P0440–P0456 or related codes may show up alongside P0468.
Common Causes of P0468
Most Common Causes
- Faulty EVAP purge flow/pressure sensor: Internal failure causing a stuck-high voltage signal.
- Damaged or corroded wiring: Open circuits, short to voltage, or high resistance in the signal or ground wire.
- Poor electrical connections: Loose, bent, or corroded terminals at the sensor or ECU connector.
- Aftermarket or incorrect replacement parts: Non-OEM sensors or purge valves that don’t match factory specs.
- Previous EVAP repairs done incorrectly: Harnesses stretched, pinched, or misrouted during other work.
Less Common Causes
- ECU/PCM internal fault: Rare, but possible if all wiring and sensor tests pass.
- Short to voltage in shared circuits: Another component on the same reference or signal line feeding voltage into the circuit.
- Water intrusion: Moisture in connectors or junction blocks near the rear of the vehicle.
- Ground issues: Rusted or loose chassis grounds causing the sensor reference to float high.
- Modified fuel or EVAP system: Custom fuel tanks, venting modifications, or emissions deletes confusing the ECU.
Diagnosis: Step-by-Step Guide
You’ll want at least a basic OBD-II scan tool, a digital multimeter, and ideally a wiring diagram for your specific vehicle. A smoke machine and a bidirectional scan tool with live data and Mode $06 are very helpful, but not mandatory for a basic diagnosis.
- Confirm the code and check for companions. Scan the vehicle and note all stored and pending codes. If you see other EVAP or voltage-related codes, address them together, as they may share a root cause.
- Check freeze-frame data. Look at engine load, RPM, fuel level, and temperature when P0468 set. This helps you reproduce the conditions later and rules out intermittent issues.
- Inspect the EVAP sensor and harness. Locate the EVAP purge flow or pressure sensor (often near the charcoal canister or on top of the tank). Look for broken connectors, rubbed-through insulation, or obvious corrosion.
- Verify power, ground, and reference voltage. With the key on, use a multimeter to check that the sensor has proper 5V reference (if applicable), ground, and supply voltage. Any missing or low reading needs to be fixed before blaming the sensor.
- Measure the sensor signal voltage. Back-probe the signal wire with key on, engine off. Compare the reading to service manual specs. A fixed high voltage (near 5V or battery voltage) usually indicates a short to power or an internal sensor fault.
- Wiggle test the harness. While monitoring live data or the signal voltage, gently move the harness and connectors. If the signal spikes or drops, you likely have an intermittent wiring or connector issue.
- Check continuity and shorts. With the sensor unplugged and battery disconnected, measure resistance between the signal wire and ground, power, and other circuits. Any unexpected continuity or low resistance suggests a short that must be repaired.
- Use scan tool data and Mode $06. On more advanced tools, monitor EVAP pressure/flow readings and related test results. If the sensor output is unrealistic compared to operating conditions, it’s likely faulty.
- Substitute a known-good sensor (if available). On some vehicles, temporarily swapping in a known-good sensor is a quick confirmation, as long as you clear codes and retest under similar conditions.
- Consider ECU testing last. Only after all wiring, grounds, and the sensor itself check out should you suspect the ECU. In many cases, a dealer-level scan tool or an automotive electronics specialist is needed to confirm.
Pro tip: Always fix wiring and connector issues before replacing the sensor. Many P0468 repairs I see are simply corroded connectors or broken wires near the rear of the car, especially in salty or coastal regions.
Possible Fixes & Repair Costs
Most P0468 fixes involve restoring proper sensor signal to the ECU. That usually means repairing wiring, cleaning or replacing connectors, or replacing the EVAP purge flow/pressure sensor itself. Typical repair costs at a professional shop range from about $100–$200 for simple wiring or connector repairs, $150–$350 for sensor replacement, and $400+ if extensive harness work or ECU replacement/programming is required. Costs vary with vehicle make, part availability (OEM vs aftermarket), labor rates in your area, and how difficult the sensor is to access.
- Repair or replace damaged wiring and terminals in the EVAP harness.
- Clean corroded connectors and apply dielectric grease where appropriate.
- Replace the EVAP purge flow/pressure sensor with a quality OEM or OE-equivalent part.
- Secure and reroute harnesses away from exhaust heat or sharp edges.
- In rare cases, replace or reprogram the ECU/PCM after confirming it’s faulty.
Can I Still Drive With P0468?
In most cases, you can still drive with P0468 without immediate danger to the engine or drivetrain. However, you may notice a check engine light, mild drivability issues, and a fuel smell. The bigger concern is that your vehicle will likely fail an emissions or state inspection until the code is fixed and the monitors run to completion. Prolonged driving with EVAP issues can also mask other problems if you get used to seeing the MIL on all the time.
What Happens If You Ignore P0468?
If you ignore P0468, you risk long-term fuel odor, potential vapor leaks, and guaranteed emissions test failures. Over time, unaddressed wiring or connector problems can worsen and start affecting other circuits. You may also miss new, more serious codes because the check engine light is already on, making it harder to catch issues early.
Related Codes
- P0474 – Exhaust Pressure Sensor Intermittent
- P0473 – Exhaust Pressure Sensor High
- P0472 – Exhaust Pressure Sensor Low
- P0471 – Exhaust Pressure Sensor Range/Performance
- P0470 – Exhaust Pressure Sensor
- P0469 – EVAP Purge Flow Sensor Circuit Intermittent
- P0467 – EVAP Purge Flow Sensor Circuit Low
- P0466 – EVAP Purge Flow Sensor Circuit Range/Performance
- P0465 – EVAP Purge Flow Sensor Circuit
- P0464 – Fuel Level Sensor “A” Circuit Intermittent
Key Takeaways
- P0468 points to an electrical issue in the EVAP purge flow sensor circuit, not just a simple gas cap problem.
- Common causes include a bad sensor, damaged wiring, and corroded connectors near the EVAP components.
- Symptoms are usually mild but include a check engine light, possible fuel odor, and failed emissions tests.
- Proper diagnosis with a scan tool and multimeter prevents unnecessary parts replacement.
- Most repairs are affordable if caught early, especially when wiring problems are addressed before they spread.
Vehicles Commonly Affected by P0468
P0468 can show up on many makes, but it’s more frequently seen on certain platforms that are sensitive to EVAP sensor and wiring issues. You’ll commonly find this code on:
- GM vehicles (Chevrolet, GMC, Buick, Cadillac) with rear-mounted EVAP canisters.
- Ford and Lincoln SUVs and trucks where harnesses run near the frame rails.
- Chrysler, Dodge, and Jeep models with EVAP sensors mounted near the tank or canister.
- Some Nissan and Infiniti vehicles that use combined EVAP pressure/flow sensors.
- Older compact cars and crossovers that have seen heavy rust or off-road use.
FAQ
Can P0468 cause my car to run rough?
Yes, it can. While many vehicles only show a check engine light, some will have a slightly rough idle, stumble, or hard starts if the EVAP system purges vapor at the wrong time due to incorrect sensor feedback.
Is P0468 the same as a loose gas cap?
No. A loose or bad gas cap usually sets codes like P0440, P0442, or P0456. P0468 is an electrical fault in the purge flow sensor circuit, not a simple pressure leak from the fuel cap.
How do I know if the EVAP sensor itself is bad?
You confirm a bad sensor by checking that power, ground, and reference signals are correct, then measuring the sensor output. If the wiring and connections are good but the signal stays stuck high or is out of spec, the sensor is likely faulty.
Can I clear P0468 and just keep driving?
<pYou can clear the code, and it may stay off for a while, but if the underlying issue isn’t fixed, P0468 will usually return once the ECU runs its EVAP tests again. Relying on clearing codes without repairs can hide developing problems.
How urgent is it to fix P0468?
It’s not an emergency like low oil pressure or overheating, but you should schedule a repair soon. Leaving P0468 unresolved can lead to emissions test failures, stronger fuel odors, and more extensive wiring damage over time.