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Hyundai Elantra 2001 P0450 and U0P00 Codes: Check Engine Light On, EVAP System Issue

Model: Hyundai Elantra Fault Code: P0450 Posted: 2015-05-18 21:51

My 2001 Hyundai Elantra (4-door, 57,000 miles) has a check engine light on. After visiting an auto parts store, two diagnostic codes were returned: P0450 and U0P00. The P045-50 code indicates an issue with the evaporative emissions system, specifically related to the fuel tank pressure sensor (FTP sensor). The U0P00 code is less common and may indicate a communication failure in the vehicle's powertrain control module or a missing diagnostic trouble code. Some sources suggest that 'U' codes are often related to data link communications. I have not made any modifications to the vehicle, nor has it experienced an accident. However, when refueling, I notice resistance in the fuel filler neck — the gas hose/muzzle clicks and does not allow full force of fuel entry until I ease off pressure on the lever. This makes filling the tank slower than usual. I'm wondering if this fuel fill issue could be related to the EVAP system or simply a mechanical obstruction. Also, I'm unsure whether 'U0P00' is correctly interpreted — could it actually be 'U0100' or another code? Or is it valid but not recognized by some diagnostic tools? Any insight into how to diagnose and potentially fix these issues at home or with a friend would be greatly appreciated.

Related fault codes

P0450

Comments (3)

Anonymous 2015-05-19 08:16

The U0P00 code is uncommon and may indicate a communication failure between the vehicle's modules. It could also mean no diagnostic trouble code was found — check the service manual for confirmation. The P0450 code points to an evaporative emissions system issue, specifically involving the fuel tank pressure (FTP) sensor. Ensure that all EVAP components are intact and properly connected. If there have been any electrical modifications or repairs in the past (e.g., fuel pump replacement, added accessories), those could interfere with the system. Also, check for any signs of leaks or blockages in the EVAP lines.

Anonymous 2015-05-19 10:33

I've not made any changes to my vehicle. The issue I'm noticing is during fueling — when I try to fill the tank, the gas hose/muzzle clicks and resists full insertion. I have to ease off pressure on the lever for it to allow fuel flow. This makes refueling take longer than normal. Could this resistance be related to a clogged or damaged EVAP system component? Or is it just a mechanical issue with the filler neck? I'm not certain if 'U0P00' is correct — could it actually be 'U0100' or another code? Is that possible, or is it a valid but unrecognized code in some systems? Any clarity on this would help me understand what's going on. Would it be safe to attempt repairs myself, or should I have a friend with experience handle it?

Anonymous 2015-05-19 10:45

The U0P00 code typically translates to 'no diagnostic trouble code found' in service manuals — this may indicate that the diagnostic tool failed to detect any active fault. It could also suggest a communication error between modules. The P0450 code confirms an issue with the evaporative emissions pressure sensor or switch, which is part of the EVAP system. This component monitors fuel tank pressure and helps prevent fuel vapors from escaping into the atmosphere. A faulty sensor can trigger the check engine light and lead to failed emissions tests. It's recommended to inspect the EVAP system for leaks, clogs, or damaged hoses. If the issue persists, a professional scan with an OBD2 scanner may be needed to confirm code accuracy.