Fault Phenomenon:
A 2019 GAC Honda HR-V with a 1.5L engine and CH2A CVT transmission, having a mileage of 61,000 km, reported difficulty starting the engine. Once started, several warning lights illuminated on the dashboard, including tire pressure (TPMS), engine malfunction (MIL), electronic parking brake, VSA, brake system, and EPS lights. The vehicle operates normally on flat roads but struggles with acceleration uphill.
Diagnostic Process:
After starting the engine, the technician observed the multiple warning lights as described. Using the Honda diagnostic tool (HDS), the error code “P0087 – Low Fuel Pressure” was detected. The P0087 code indicates a problem with the high-pressure fuel system. The powertrain control module (PCM) uses feedback from the fuel pressure sensor to regulate the fuel pump’s pressure. If the actual pressure deviates significantly from the target, the PCM registers this fault.
The P0087 code triggers when the fuel pressure is significantly lower than the target pressure (2.5 MPa to 15.0 MPa). If the fuel pressure remains below or above the target pressure for 4 seconds, the PCM detects a fault.
Analysis:
The low-pressure fuel system involves components like the PCM, fuel lines, fuel pump, fuel filter, and pressure regulator, while the high-pressure system includes the high-pressure fuel pump, distribution pipe, pressure sensor, fuel control valve, and injectors. The high-pressure fuel pump is driven by the camshaft and is responsible for compressing fuel to high pressure for injection into the engine.
After reviewing the electrical circuits, we found that the low-pressure fuel pump and high-pressure fuel system circuits seemed intact. As the fault code was only P0087, it indicated an issue with the high-pressure fuel system. Possible causes were narrowed down to:
- Fuel line obstruction
- Clogged fuel filter
- Fuel pressure regulator malfunction
- Internal failure of the low-pressure fuel pump
- Fuel injector stuck open
- Faulty high-pressure fuel pump
- Faulty fuel pressure sensor
- High-pressure pump camshaft failure
Diagnosis:
After clearing the fault codes, the HDS showed an abnormal result during the fuel pressure test. The fuel pressure for the direct injection system was 0 MPa, compared to a normal value of 4.0 MPa. With further testing, it was determined that the high-pressure fuel pump was malfunctioning. No unusual noise or vibration was detected from the pressure relief valve, indicating the pump was faulty.
Solution:
Replacing the high-pressure fuel pump resolved the issue. After ensuring no fuel leaks, the system was reassembled, and the engine started. A road test confirmed the fault was eliminated, and all systems operated correctly.
Summary:
In this case, the hard starting was caused by a faulty high-pressure fuel pump, which prevented proper fuel injection at startup and during heavy load conditions. After eliminating the low-pressure system components and confirming the issue with the high-pressure system, the pump was replaced, restoring normal engine operation. This case highlights the importance of diagnostic tools to pinpoint complex issues, particularly when multiple warning lights appear.
