P0748 code definition
This code stands for Pressure Control Solenoid Electrical. In some vehicle makes, this code may have a different definition, so be sure to check on the specific for your vehicle.
What the P0748 code means
The pressure control solenoid manages transmission line pressure by monitoring various driving conditions such as speed, engine load, and throttle position. It sends messages to the vehicle’s computer in order to facilitate the appropriate pressure for those specific conditions. Signals are sent in the form of voltage readings, and if these readings indicate fluid pressure which does not match the expected measurements, this code will set.
What causes the P0748 code?
The pressure control solenoid electrical may set an error if any of the following conditions exist:
- Contaminated or dirty transmission fluid
- Low transmission fluid
- Hydraulic clogs inside the transmission fluid passageways
- A bad electronic pressure control solenoid
- Mechanical internal transmission failure
- A faulty TCM (transmission control module)
- A faulty PCM (rarely)
What are the symptoms of the P0748 code?
If this code is stored you may not notice any discernible symptoms, or you may notice severe shifting problems such as a lack of shifting altogether. The engine may stall at idle, shifting may be harsh or there could be slippage, or the transmission could overheat. Other signs include decreased fuel economy and a lit malfunction indicator lamp (MIL). Other codes may set, such as those related to gear ratio, shift solenoids, or transmission slippage.
How does a mechanic diagnose the P0748 code?
Identifying the source of this error may include:
Verifying the stored code(s) and recording data with a scanner hooked up to the vehicle’s computer
Monitoring the scanner while driving to check whether the PCM is commanding the pressure control solenoid
Checking the transmission fluid level and condition
Visually inspecting the wiring and connectors for damage like corrosion or breaks
Performing pinpoint tests such as voltage and continuity tests on the pressure control solenoid circuit
Using a pressure gauge to measure the solenoid’s function
Removing the transmission pan to check for metal shavings or debris which indicate that internal mechanical transmission failure has begun
Common mistakes when diagnosing the P0748 code
It’s not uncommon for this error to be chalked up to an engine misfire issue, or to assume that the high pressure pump is the culprit. Wiring and other involved circuitry may be overlooked as possible causes. It’s important to make sure that a complete diagnostic process is carried out.
How serious is the P0748 code?
Transmission issues should always be addressed as quickly as possible. Even if the problem has not advanced to the point that internal mechanical failure has occurred, experiencing symptoms means that there is an issue which could become serious in very short order.
What repairs can fix the P0748 code?
Possible fixes for this DTC include:
- Repairing pressure control circuitry such as wiring and connectors
- Replacing the pressure control solenoid
- Replacing the electronic pressure regulator
- Rebuilding or replacing the complete transmission, including torque converter
- Flushing and replacing the transmission fluid
- Replacing the TCM
Additional comments for consideration regarding the P0748 code
Checking the transmission fluid condition is a crucial step in rectifying any transmission-related error. If the fluid appears or smells burned or is a dark, opaque color, it is almost a certainty that the vehicle has been operated at a low fluid level. This means that catastrophic internal damage may have already occurred.
While some parts of the diagnostic process may be done at home, such as assessing the transmission fluid (if you have a dipstick), transmissions are not typically the kind of project you want to do in the driveway. It’s best to consult a qualified professional as soon as possible.
Need help with a P0748 code?
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