Circuit Description

WARNING: This page is about a different car, the 2002 Toyota Land Cruiser. However, it is still accessible from the selected car via links, so may be relevant.

Fuel pump operating speed is controlled by engine operating conditions such as: starting, idling, light load or heavy load. Engine Control Module (ECM) delivers an input signal from FPC terminal on ECM to FPC terminal on fuel pump Electronic Control Unit (ECU) in accordance with engine operating condition. Fuel pump ECU uses this input signal to determine how much voltage should be delivered to fuel pump for varying fuel pump operating speed. When engine starts, or engine is under heavy load at high speeds, ECM delivers input signal of approximately 3.8 volts to fuel pump ECU. Fuel pump ECU then delivers approximately battery voltage to fuel pump and fuel pump operates at high speed. When engine is under heavy load at low speeds, ECM delivers an input signal of approximately 2.5 volts to fuel pump ECU. Fuel pump ECU then delivers approximately 10 volts to fuel pump and fuel pump operates at medium speed. When engine is idling or under light loads, ECM delivers an input signal of approximately 1.3 volts to fuel pump ECU. Fuel pump ECU then delivers approximately 8.5 volts to fuel pump and fuel pump operates at low speed. DTC is set when ECM detects an open or short in a fuel pump ECU circuit with engine speed of 1000 RPM or less. Possible causes are:

Fuel pump ECU circuit is open or shorted.
Defective fuel pump ECU.
Defective fuel pump ECU power source circuit.
Defective fuel pump.
Defective ECM.