Quick Answer
The P2404 code means the EVAP leak-detection pump sense circuit did not respond within its calibrated range or performance pattern. It does not prove the pump itself is bad or that the fuel cap is leaking. Save the complete scan record first, then identify the VIN-specific pump, feedback method, wiring and test procedure before replacing anything.
What Does the P2404 Code Mean?
The P2404 code is standardized as “Evaporative Emission System Leak Detection Pump Sense Circuit Range/Performance.” The EVAP system stores gasoline vapors instead of releasing them into the air. On vehicles that use an electric leak-detection pump or an evaporative leak check module, the ECM evaluates a feedback or “sense” result while the system tests its ability to create and monitor pressure or vacuum.
“Sense circuit” is broader than one universal sensor wire. A design may infer pump movement from a switch, electrical current, or pressure/vacuum behavior inside an integrated module. Obtain the pump location, connector view, feedback PID and self-test sequence from VIN-specific service information.
“Range/performance” means the response did not match the ECM’s expected functional pattern. Causes can be electrical, mechanical, pneumatic, contamination-related or software-related. It is a monitored result, not a parts verdict.
P2403 vs. P2404, P2405, P2406 and P2407
| Code | General description | Key distinction |
|---|---|---|
| P2403 | Leak-detection pump sense circuit/open | The ECM classifies the feedback path as a circuit or open fault. |
| P2404 | Leak-detection pump sense circuit range/performance | The feedback or system response fails the expected functional pattern. |
| P2405 | Leak-detection pump sense circuit low | The electrical classification is low; it does not mean low tank pressure. |
| P2406 | Leak-detection pump sense circuit high | The electrical classification is high; it does not mean excessive pump output. |
| P2407 | Leak-detection pump sense circuit intermittent/erratic | The feedback is unstable or disappears intermittently. |
An OEM example shows why VIN research matters. Subaru bulletin 09-107-23 covers only specified Ascent model years and links P2404 with an ELCM pump that may temporarily seize, drain-tube contamination and revised ECM logic. That repair path cannot be transferred automatically to another Subaru or another brand.
P2404 Symptoms and Likely Causes
The EVAP monitor runs only under selected operating or key-off conditions, so acceleration and idle may feel normal. The code still matters because readiness may remain incomplete, and vapor leakage or liquid-fuel contamination needs prompt attention.
The MIL may be the only obvious symptom when the failure occurs during an automatic EVAP self-test.
P2404, pending status or an incomplete EVAP monitor may prevent an emissions-test pass.
Related pump, pressure-sensor, switching-valve or leak codes can identify which test failed first.
Strong gasoline odor, visible wetness or difficult refueling requires separate safety evaluation.
Practical cause-checking order
- Connector and harness exposure: water, salt, impact, terminal spread, corrosion or chafing near the tank, canister or pump.
- Power, ground or battery condition: voltage drop, weak key-off supply, a blown fuse or poor ground can distort operation and feedback.
- Air, vapor and drain paths: pinched hoses, blocked filters, restricted drains, wrong routing or damaged seals can prevent the expected response.
- Liquid or debris intrusion: water, oil, dust or liquid fuel can contaminate the module, pump, filter or canister. Tank topping-off can saturate the canister.
- Pump or integrated module fault: an internal switch, motor, diaphragm or sensing element may fail after external paths pass.
- Calibration or ECM path: a VIN-specific bulletin may prescribe updated logic. Consider controller hardware last.
Recent work is an important clue. If P2404 appeared after fuel-tank, canister, collision, exhaust or rear-underbody service, recheck crushed hoses, swapped lines, unsecured connectors, missing clips and disturbed grounds before ordering a pump.
How Serious Is P2404, and Can You Drive?
When the P2404 code is the only fault, with a steady MIL, normal operation, no odor and no fuel leakage, a short light-load trip to a diagnostic location may be reasonable when the owner’s manual allows it. Do not postpone service: readiness may remain incomplete, and another fault could be hidden behind the same warning lamp.
Stop and arrange a tow if you see liquid fuel, smell a strong or worsening raw-fuel odor, see smoke, notice a burning smell, experience repeated stalling or unsafe power loss, or have a flashing MIL with severe misfire. Those conditions are not a normal consequence of P2404 and require immediate safety assessment.
EVAP service involves flammable vapor near the fuel tank. Use approved ventilation, eliminate ignition sources, follow OEM pressure-relief and battery procedures, and never use shop air or unapproved smoke fluid. For underbody access, use rated lift points and supports, never a jack alone.
How to Diagnose P2404 in the Right Order
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Save every code, status and test result
Scan all modules before clearing. Record current, pending, permanent and history status; freeze frame; failure order; calibration IDs; readiness; Mode $06 results; and related EVAP codes. Companion pump, valve or pressure-sensor codes can change the branch. Note fuel level, refueling, weather, battery history and recent repairs.
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Identify the VIN-specific EVAP architecture
Locate the pump, canister, filter, valves, drain tube and integrated sensors in the service manual. Obtain connector views, diagrams, monitor criteria and current bulletins. Confirm whether the assembly is called LDP, DMTL, ELCM or something else. Never transfer Subaru thresholds, test duration or software instructions to another vehicle.
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Inspect the physical and electrical paths safely
With the system safe, inspect the fuel cap, filler area, lines, filters, drain, housing, connector seals, pins, harness retainers and grounds. Look for vapor stains, liquid fuel, water, oil, dust, rodent damage, impact and heat. After recent work, compare routing and connector seating with the diagram.
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Prove supply, ground, feedback and sealing
Follow the OEM pinpoint test with a multimeter, current clamp and, when specified, approved EVAP test equipment. Measure loaded voltage drop and terminal tension correctly. If the system cannot create the expected pressure or vacuum, isolate restrictions, leaks and valve sealing before blaming feedback.
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Compare command with actual response
When supported, run the prescribed EVAP or pump test while watching command, feedback, tank pressure, valve state and monitor results. A command with no response narrows the search but does not distinguish a failed pump from missing power, poor ground, blockage or unsupported scan coverage.
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Confirm the failed item and required setup
Condemn the pump, ELCM, canister, sensor or valve only after its external circuit and physical path pass. Check calibration applicability before software and use the OEM-authorized programming process; CR Max P is not a substitute. Restore clips and seals, perform required setup, then verify the monitor.
Specifications are vehicle-specific. There is no universal P2404 voltage, resistance, current, pressure, vacuum, fuel-level window, pump run time or drive cycle. Use only the units, connector loads, test conditions and pass/fail limits for the exact VIN and current service information.
P2404 Repairs and Typical Costs
The repair follows the failed test: wiring work, restoring a restricted hose/filter/drain, replacing a proven pump or ELCM, replacing a contaminated integrated canister, or applying an eligible OEM calibration update. A gas cap is the fix only when testing proves its sealing problem caused the result.
| Possible path | Current US estimate |
|---|---|
| Check-engine-light diagnosis and testing | $122–$233 |
| Fuel evaporative canister replacement, only when the confirmed failed pump/module is serviced with that assembly | $555–$640 |
| Connector, harness, hose, filter or drain-path repair | VIN-specific quote |
| Separate leak-detection pump or ELCM replacement | VIN-specific quote |
| OEM software update or control-module work | VIN-specific quote |
RepairPal’s national estimates were updated August 7, 2026 and exclude location, taxes, fees and related work. The rows are alternatives, not amounts to add. Because the pump may be separate, inside an ELCM or bundled with a canister, request a VIN-based quote after isolation.
Using iCarsoft CR Max P for P2404
On a supported vehicle, iCarsoft CR Max P can preserve P2404 code status and available freeze frame, review readiness and monitor results, display ECU-provided live data and save a report. EVAP PIDs, system tests and active commands depend on the exact VIN, ECU and software, so confirm coverage before purchase.
Evidence-first EVAP diagnosis
iCarsoft CR Max P
Preserve DTC evidence, review supported EVAP data and monitor results, and compare available command with feedback before replacing an emissions component.
Check current CR Max P price and availabilityCheck CR Max P compatibility by VINBefore an EVAP system test, read its OEM conditions. If a function is absent, that is a coverage limitation, not evidence of pump or ECM failure. Hearing a pump run also does not prove adequate current, airflow, sealing or feedback accuracy. Pair scan evidence with electrical and leak testing.
Know the measurement boundary. iCarsoft CR Max P does not directly measure circuit voltage drop, current, resistance, terminal tension, vapor leakage, physical pressure/vacuum, hose restriction or internal pump condition. Use a suitable multimeter, current clamp, approved EVAP smoke/pressure-vacuum equipment and visual inspection alongside scan data.
How to Verify a P2404 Repair
Save a post-repair scan and compare it with the original. Confirm connectors, clips and hoses are restored; no leakage or odor remains; battery condition is suitable; and calibration matches applicable bulletins. Clear erasable DTCs only after saving evidence and through the allowed procedure.
Run the exact EVAP test or monitor conditions. Verify P2404 does not return as current or pending, companion codes stay absent, and available command, feedback and monitor results agree. One clean idle proves little because many tests need a particular fuel level, soak, temperature or key-off sequence.
Finally, recheck readiness after an appropriate operating period. Do not promise a universal number of starts or miles; monitor conditions differ by calibration and may be affected by ambient temperature or fuel level. If the monitor will not run, diagnose the unmet enable condition instead of repeatedly clearing codes, disconnecting the battery or replacing another part.
A permanent P2404 can remain immediately after a successful repair. If the vehicle stores it as a permanent DTC, a scan tool or battery disconnect cannot erase it. Once current and pending faults are absent, the OBD system removes the permanent record only after the applicable monitor reruns and passes.
Related EVAP Code Guides
P2404 Frequently Asked Questions
Does P2404 mean the leak-detection pump is bad?
No. P2404 records an out-of-range or incorrect performance result from the pump’s sense path. A failed pump is possible, but power, ground, feedback wiring, a blocked hose or filter, contamination, leakage, valves and vehicle-specific software can produce a similar result. Confirm the architecture and follow its pinpoint test.
What is the difference between P2404 and P2407?
P2404 is a range/performance classification: the response does not match the expected functional pattern. P2407 is intermittent/erratic: the sense signal becomes unstable or drops out. Both require circuit and physical checks, but P2407 places more emphasis on intermittent terminals, harness movement and moisture.
Can a loose gas cap cause the P2404 code?
It is not the default conclusion. A loose or damaged cap more directly causes an EVAP leak code, while P2404 concerns the leak-detection pump sense response. On some calibrations a system leak may prevent the expected test result, so inspect the cap but do not replace it without evidence.
Can I drive with P2404?
A short light-load trip may be reasonable when the MIL is steady, the vehicle operates normally, there is no fuel odor or leak, and the owner’s manual permits it. Stop for liquid fuel, strong vapor odor, smoke, burning smell, severe misfire, stalling or unsafe power loss.
How much does P2404 cost to repair?
Current US check-engine-light diagnosis averages $122–$233. A confirmed fuel evaporative canister replacement averages $555–$640, but that figure applies only when the failed pump or module is serviced with the canister. Wiring, separate pumps, integrated ELCMs and software require a VIN-specific quote.
Can iCarsoft CR Max P diagnose P2404?
On a supported vehicle, CR Max P can preserve codes and freeze frame, view available EVAP data and monitor results, and may offer an EVAP test or active command. It cannot physically measure voltage drop, pump current, terminal tension, leakage, pressure/vacuum or restrictions, and it does not replace OEM programming procedures.
Technical and cost references
- SAE J2012_202509, Diagnostic Trouble Code Definitions, revised September 1, 2025, and the current J2012DA_202607 digital annex, dated July 29, 2026.
- Subaru TSB 09-107-23, DTC P2404 / Reprogramming Files, dated July 18, 2023, for specified 2019–2023 Ascent vehicles and an OEM-specific ELCM/software example.
- Subaru TSB 09-128-24, DTCs P2404, P0016-19, P0021, & U0100 Diagnostic Procedures, dated October 8, 2024, for specified 2022–2024 BRZ vehicles and an OEM-specific test sequence.
- RepairPal Check Engine Light Diagnosis & Testing Cost Estimate, $122–$233, updated August 7, 2026.
- RepairPal Fuel Evaporative Canister Replacement Cost Estimate, $555–$640, updated August 7, 2026.
Product information: Official iCarsoft CR Max P page.
Editorial note: Educational information only. This guide does not replace VIN-specific service information, fuel-vapor precautions, approved EVAP leak-test equipment, safe vehicle lifting or diagnosis by a qualified technician. Never introduce shop air, an ignition source or unapproved smoke into the fuel-vapor system, and do not bypass an emissions component.
