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2009 Hyundai Accent P0451 and P0496 EVAP Codes Reappear After Clearing - O2 Sensor or System Leak?

Model: 2009 Hyundai Accent Fault Code: P0132 Posted: 2017-03-16 15:11

2009 Hyundai Accent GS (110,000 miles, 5-speed manual) — Recently experienced recurring DTCs: P0451 (Evaporative Emission System Pressure Sensor/Switch Range/Performance), P0496 (Evaporative Emission System High Purge Flow), and now P0328 and P0132. The vehicle has been through multiple emission component replacements including OEM gas cap, FTPS, PCSV valve, CCV, and all rubber hoses — all confirmed intact. After clearing the codes via OBD-II, the MIL light typically reactivates after ~20 miles as expected. However, today I noticed that instead of P0451 or P0496 returning, new codes P0328 (O2 Sensor Circuit Low Signal) and P0132 (O2 Sensor Circuit Range/Performance — Bank 1, Sensor 1) appeared. I’ve heard about the characteristic 'clicking' noise in 1.6L Hyundai engines, and have already replaced the PCSV valve and all emission-related components. My question: Could this be a failing O2 sensor that has been silently causing the EVAP codes to remain pending? If I replace the O2 sensor, will it resolve both the new P0328/P0132 and eliminate the earlier EVAP codes? I understand the technical definitions of these codes but lack advanced diagnostic tools. As a college student with limited access to professional diagnostics, I need reliable insight to keep my car running without MIL illumination — especially in Miami’s hot climate. Additional note: The vehicle was originally registered in Illinois and has now been driven in Florida’s high-heat environment for several years. Could temperature extremes be contributing to intermittent failures? I’m prepared to share more data (email: taymac1112@gmail.com) if needed. Any input would be greatly appreciated. UPDATE: After troubleshooting, I discovered oil seepage from the throttle body directly onto the PCSV connector harness — a known issue in high-mileage 1.6L engines. Cleaning and re-taping exposed wiring resolved the codes temporarily. However, the EVAP codes have returned after refueling, and I’m now considering a professional smoke test to identify potential leaks in the evaporative system. I’ve attached fuel trim data (3000 RPM steady throttle) and freeze frame details for P0451. If anyone sees anomalies or patterns, please advise.

Related fault codes
P0132P0328P0451P0496
Comments (10)
Anonymous 2017-03-16 18:10

To better diagnose the issue, please share fuel trims, O2 sensor voltage readings, and freeze frame data. A professional diagnostic scan is recommended to avoid unnecessary part replacements.

Anonymous 2017-03-20 06:47

I captured city driving data: initial start under load, followed by steady-state throttle operation. My OBD-II adapter in the torque app failed to record short-term fuel trims — I’ll try a different scanner later today to retrieve accurate fuel trim values for idle and 3000 RPMs.

Anonymous 2017-03-20 10:02

O2 sensor signals appear normal. This suggests P0132 is not due to sensor failure. Please provide freeze frame data for P0132, along with long-term and short-term fuel trims at idle and under load (30 seconds minimum). Also share freeze frame details for P0496. Note: Several known Hyundai-specific causes exist for P0496 — check the forum threads for references.

Anonymous 2017-03-22 16:58

All codes are currently pending except P0446, which is active and set. I’ve attached freeze frame data for P0446. A pending P0172 (system too rich) also appeared recently. This raises concern — could the engine be receiving excess fuel via the purge valve during refueling? The vehicle has difficulty starting after filling up, dies intermittently, and idles erratically until revved back to normal. Is this a sign of an electrical or emission system issue?

Anonymous 2017-03-23 09:34

P0451, P0496, and P0446 are related EVAP system issues — they may not directly affect drivability but indicate a potential leak. Since P0446 is active, test the vent valve circuit for proper operation using voltage or ohm checks. BBBind.com offers detailed electrical schematics. Have you confirmed the canister vent valve was replaced? If so, consider a smoke test to detect leaks in hoses — this is difficult to diagnose without such testing.

Anonymous 2017-03-23 14:14

Thanks! I’ll perform an ohm and voltage test on the entire circuit. Here’s the short-term fuel trim data collected at 3000 RPM steady throttle. Important note: After refueling, the car struggles to start — it dies multiple times and idles erratically until revved; once recovered, it runs smoothly. This behavior is unusual and may point to a deeper issue.

Anonymous 2017-03-23 16:54

The P0172 code appearing after refueling could indicate excess fuel flow from the evaporative canister through the purge valve. Since P0446 is active, prioritize fixing that first. Fuel trims at 3000 RPM appear normal — this suggests the issue may be upstream or related to a leak in the EVAP system.

Anonymous 2017-03-28 17:39

I found the root cause — at least I believe so. The PCSV valve tested fine on ohm resistance, but its connector showed poor voltage readings. After removing the intake assembly and inspecting the harness, I noticed oil seepage from the throttle body — a known high-mileage issue in 1.6L Hyundai engines. This oil was directly contacting the PCSV connector, which is seated in an upward-facing position. Using a cotton swab, I found oil inside the male plug of the wiring harness. I cleaned both the connector and the valve prongs with ISP (isopropyl alcohol), re-taped a chafed wire running under the throttle body, and after multiple test runs, all codes disappeared. The car started immediately after refueling (half tank) and now runs much smoother — especially at low RPMs. This fix cost me nothing. Thanks to everyone for the guidance!

Anonymous 2017-03-30 08:22

UPDATE: Codes have returned. I’ve posted freeze frame data for P0451 (EVAP Pressure Sensor/Performance) and P0496 (High Purge Flow). The vehicle is now being taken to a mechanic this weekend. I’ll share full results after the service. After months of troubleshooting, I’m considering switching to an American-made vehicle. Please review the data below for any anomalies: P0451: $07EF — Evaporative Emission System Pressure Sensor/Switch Range/Performance P0496: $07EF — Evaporative Emission System High Purge Flow (Pending) Freeze Frame Data (P0451): - FUELSYS1(): CL - FUELSYS2(): -- - LOAD_PCT(%): 38.8 - ECT(°F): 321 - SHRTFT1(%): -4.7 - LONGFT1(%): 1.6 - MAP(psi): 1.0 - RPM(rpm): 2393 - VSS(mph): 28 - SPARKADV(°): 35.0 - IAT(°F): 170 - TP(%): 14.1 - RUNTM(sec): 171 - EVAP_PCT(%): 100.0 - FLI(%): 73.7 - BARO(psi): 2.1 - VPWR(V): 14.159 - LOAD_ABS(%): 36.9 - EQ_RAT(): 0.999 - TP_R(%): 7.1 - AAT(°F): 163 Any insights from this data would be greatly appreciated.

Anonymous 2017-03-30 11:22

A hands-on diagnostic by a certified auto shop is strongly recommended. Before any repair begins, discuss with the technician what warranty or assurance they offer for accurate diagnosis and fix — especially since EVAP issues can be intermittent. If the vehicle is under warranty, ensure that repairs are covered. A professional smoke test may be necessary to detect hidden leaks in the evaporative system.