Hello, The first code is a corelation issue as shown below, a scan tool will verify the sensor data which they most likely did when they pulled the codes. The other code if you wrote it correctly is a fuel system code. If the cooling system level is low, this would be a good idication of their diagnosis being correct, but it is possible the ECT or EOT sensor is at fault. If the fuel system is having an issue such as an injector leaking fuel, this would cause the oil level to be higher and not have a milky look to the engine oil.
P012F - Engine Coolant Temperature/Engine Oil Temperature Correlation
Description:This DTC sets when the maximum difference between the engine coolant temperature and the engine oil temperature exceeds the calibrated threshold for a prescribed amount of time depending on engine operating conditions.
- Low engine coolant level
- Cooling system flow concerns
- Cooling system pressure loss
- ECT sensor
- EOT sensor
- Oil cooler flow concerns
Diagnostic Aids:The threshold value varies between 9°C (16°F) and 17°C (30°F) depending on the speed and load applied to the vehicle.
P0087 - Fuel Rail/System Pressure - Too Low
Description:The powertrain control module (PCM) regulates the fuel rail pressure by controlling the fuel volume control valve and fuel pressure control valve. When the PCM is no longer capable of maintaining the fuel pressure the DTC is set.
- Low pressure fuel system
- Fuel pressure control valve stuck open
- Fuel volume control valve stuck closed
- Leaking fuel injector
Diagnostic Aids:Use the high pressure fuel injection pump 4-pin inline connector to diagnose the fuel volume control valve and fuel pressure control valve.