P1641 Code failures by brands


Description of DTC code P1641

The fuel pump is enabled for a few seconds after turning the key to the ON setting. With this, the pump is primed and the fuel system is pressurized. In case the engine does fail to crank or the key is in the ON position, the Powertrain Control Module (PCM) deactivates the pump according to a timing schedule set by the manufacturer. For the fuel pump to operate, the PCM must receive signals from various sensors indicating that the engine has started and is operating regularly. In this sense, the most vital signal is from the engine speed sensor, which relays the engine RPM.

When the ignition circuit is turned on, a dedicated relay that delivers power to the fuel pump is also turned on. With this relay, a low amperage circuit is used to close a high amperage circuit through the activation of an electromagnet, which in turn drives a moving contact point with a stationary live contact point. This whole process indicates that the PCM electronics, being delicate, does not require sending high amperage current to an electrical consumer, which in this case is the fuel pump.

However, when there is prolonged use, the contact points of the high amperage switch in the relay may be damaged to the point of burning out and as an end result, the contact is no longer usable. Once this happens, the PCM interprets this as a circuit fault and will set the P1641 OBDII diagnostic code.

Symptoms of fault code P1641

  • Check Engine lamp illumination.
  • The engine does not start, although it may be an intermittent condition.
  • If the engine starts, it stops or shuts off unexpectedly.

Causes of OBD2 P1641

The reasons for which the P1641 OBD2 fault code is set are:

  • Circuit wires or connectors may have been damaged.
  • The circuit may be open or shorted.
  • If the fuel pump has resistors, the resistors may be faulty.
  • The fuel pump motor may be faulty.
  • The Fuel Pump Control Module may be in poor condition.

Possible solutions of the DTC code P1641

The steps to follow to correct the DTC P1641 OBDII code are:

  • Consult the Technical Service Bulletins.
  • Verify that the battery has a sufficient charge level for the good operation of the fuel pump control circuit. If deficiencies are found, make the appropriate corrections.
  • Check the fuel pump relay to verify that it is not in bad condition or that its pin connections are not damaged. Repair as necessary.
  • Inspect all fuel pump-related wiring and connectors. If these tests detect burned wires or corroded connectors, make repairs as necessary.
  • Measure the input voltage, resistance, ground signal, and continuity of the circuits related to this code. If these readings are inconsistent with the values specified by the manufacturer, make the appropriate repairs.

Codes related to P1641

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