P0748 - TRANSMISSION FLUID PRESSURE (TFP) SOLENOID – ELECTRICAL

POST UPDATED IN January, 2023

Description of DTC code P0748 Generic

Diagnostic code P0748 OBD2 is established at the time the PCM (Powertrain Control Module) finds a fault in the transmission pressure control solenoid. The solenoid aims to regulate the transmission flow pressure, ensuring efficient transmission operation in every gears.

When initiating a gear change, the pressurized fluid is diverted in each hydraulic circuit by the solenoid, maintaining the pressure required to keep the clutches and the gears engaged.  If the pressure is not sufficient, the transmission may slide, while if the pressure exceeds the limit, the transmission may overheat and components of the transmission may be damaged.

In order to maintain the pressure of the transmission fluid within the given range, the Powertrain Control Module constantly monitors the actual fluid pressure at various operating parts in the transmission, then compares the reading obtained with the wished pressure. If the PCM finds an electrical fault in the solenoid control circuit, causing the actual pressure to be delayed from the set pressure, this code is set and the Check Engine light is illuminated.

Symptoms of fault code P0748 Generic

  • MIL light on.
  • Established other codes related to transmission.
  • Transmission slippage.
  • Transmission overheats.
  • Fuel consumption increases.

Causes of OBD2 P0748 Generic

These are the causes of DTC code P0748 OBDII:

  • Cables or connectors in bad condition, causing a short circuit.
  • The transmission fluid may be degraded.
  • Control solenoid may be defective.
  • Transmission valve body is defective.
  • Obstructions in the fluid flow in the body of the valve.

Possible solutions of the DTC code P0748 Generic

To solve the problems generated by the fault code P0748 OBD2 you must do the following:

  • Determines the level and condition of the transmission fluid. If the level is too low, you must adjust it. Also check for fluid leaks and repair if so. If you notice that the fluid has a dark color, must be replaced as well as the fluid filter and oil sump.
  • Using the manufacturer's manual, locate the transmission cables and check the condition of each one. If there are burned, worn or corroded cables you should replace them.
  • It measures resistance and continuity levels as well as ground integrity in all cables related to this code. Consult the service manual for manufacturer's specifications. Note that these tests must be performed with the cables disconnected from the control modules.
  • Although electrical values vary by manufacturer, there must be 0 resistance in the circuits and connectors. If not, and exceeds the manufacturer's limit, the circuit is shorted. Change the cables that you consider to be in bad condition.

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