Vehicle: 2017 Hyundai Santa Fe, AWD, L4-2.4L, Automatic Transmission/Transaxle

Mileage: 129,901 Miles

Problem: The Santa Fe was in the shop because the malfunction indicator light (MIL) was on and the engine ran poorly.

Case Details: With a scan tool, the technician found two diagnostic trouble codes (DTCs):

• P0087 - Fuel Rail/System Pressure Too Low
• P0191 - Fuel Rail Pressure Sensor Circuit Range/Performance

He found the high-side fuel pressure was OK at idle, but when increasing RPM, it dropped to 60-70 PSI, started to run poorly and the MIL began flashing. The fuel supply pressure-tested OK with a gauge.

The technician replaced the high-pressure pump, which put the pressure within specifications with no returning DTCs. The technician drove the vehicle to get it ready for a smog check. All the readiness monitors ran to completion except the EVAP monitor. Also, the P0087 permanent DTC could not be erased, even after several drive cycles. DTC P0191 could be erased. The technician didn’t see anything wrong with fuel pressure data. A call went out to an ALLDATA Tech-Assist consultant.

The consultant advised that permanent DTCs need to run through the associated monitor several times and pass to clear the code. They cannot be cleared with a scan tool and may also persist even after the battery has been disconnected. In most cases, it takes about three successful drive cycles, which often include the engine to be started cold and warmed up past a certain threshold. It might take several test drives over several days to clear the DTC.

If you have no warning lights and no other DTCs, and the vehicle runs and drives fine, the DTC will clear by itself as the customer drives it.

Confirmed Repair: The technician took the vehicle on a longer drive and made sure the fuel system monitored completely. On the next key cycle, the permanent DTC magically cleared. Problem solved!