Fuel Pump failure is a common cause of triggering the engine fault code. Data shows that approximately 30% of P0087 (low fuel rail pressure) fault codes directly result from pump failures. For instance, in the case reported by Automotive News in 2022, a certain brand of vehicle model saw its fault code trigger rate soar by 52% when the fuel pump pressure output dropped to 60% of the designed value (such as 45psi). Industry terms such as “oil rail pressure deviation” (±5psi is the upper tolerance limit) are directly related to the OBD-II protocol (SAE J1979 standard). When the sampling frequency of the pressure sensor reaches 100Hz, if a pressure fluctuation of more than 20% is detected within 10ms, the ECU will immediately record the fault.
The degradation of pump performance will disrupt the air-fuel ratio control logic. Experimental data show that when the pump flow rate decreases by 30% from the nominal value (such as 150L/h), the fuel injection pulse width needs to increase by 15% compensatorily. However, after exceeding the ECU closed-loop control range (λ value deviation ±0.1), P0171/P0174 will be forcibly triggered (the system is too rare). A typical case is the 2020 investigation report of the National Highway Traffic Safety Administration (NHTSA) of the United States: Due to the wear of the fuel pump impeller of a certain car manufacturer, the flow rate decreased by 25%, causing 140,000 vehicles to have a batch of fault codes. The average repair cost reached 650±100, and the recall budget exceeded 90 million.
The risk of false alarms from sensors has risen simultaneously. The fuel pressure sensor (FPS) may output noise signals when the pump is abnormal. If the sampling standard deviation exceeds 0.5V (10% of the full scale 5V), it will be misjudged as a sensor failure. For instance, Ford’s 2021 Technical bulletin pointed out that due to poor contact in the oil pump circuit, voltage glitches (amplitude ±2V) were caused, which were mistakenly recorded by the ECU as P0193 (high input of the oil pressure sensor circuit), with a misdiagnosis rate of 37%. The industry solution needs to be combined with the Fault Tree Analysis (FTA) model to reduce the bit error probability to less than 5% by synchronously monitoring the correlation between the pump current (normal range 4-8A) and the pressure curve (R²≥0.95).
The indirect failure chain is equally significant. The failure of the fuel pump can trigger secondary codes such as P0300 (random fire failure) : When the fuel supply from the pump is insufficient, causing the cylinder pressure to fluctuate by more than 15%, the crankshaft position sensor (CKP) detects that the rotational speed deviation exceeds 200rpm and activates the fire failure detection algorithm (analyzing every 200 revolutions). The empirical evidence comes from Toyota’s 2023 hybrid model research: The failure of the fuel pump module leads to an 8-fold increase in the underignition rate, a 40% increase in the probability of triggering an emission over-limit warning (P0420), and directly shortens the lifespan of the three-way catalyst to 65% of the original design of 100,000 miles.
To sum up, fuel pump failures are strongly associated with the engine code through paths such as pressure loss, flow attenuation, and electrical interference. The technical specifications require that during maintenance, the performance parameters of the pump (such as flow ≥95% of the nominal value) be detected first, and the system risk be controlled within the ISO 26262 ASIL-B safety level.