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Technical Description of OBD-II Trouble Code
Electrical Issue with Pressure Control Solenoid A
What does that signify?
This is a standard diagnostic trouble code (DTC) for transmission and is usually applicable to OBD-II vehicles with automatic transmissions.
This may include vehicles from various manufacturers such as Ford, Mercury, Lincoln, Jaguar, Chevrolet, Toyota, Nissan, Allison/Duramax, Dodge, Jeep, Honda, Acura, etc. Although it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration.
When the P0748 OBD-II trouble code is triggered, it means that the Powertrain Control Module (PCM) has detected a problem with the Transmission Pressure Control Solenoid “A”. Most automatic transmissions have at least three solenoids, namely solenoid A, B, and C. The trouble codes associated with the “A” solenoid are codes P0745, P0746, P0747, P0748, and P0749. The specific code is determined by the particular malfunction that alerts the PCM and causes the Check Engine Light to illuminate.
The purpose of the Transmission Pressure Control Solenoids is to regulate the fluid pressure for the proper functioning of an automatic transmission. The PCM receives an electronic signal based on the pressure within the solenoids. An automatic transmission operates through bands and clutches that change gears by applying fluid pressure at the right place and time. Based on signals from devices that monitor the vehicle’s speed, the PCM controls the pressure solenoids to direct fluid at the appropriate pressure to different hydraulic circuits, thereby changing the transmission gear ratio at the correct moment.
The code P0748 is triggered when the Pressure Control Solenoid “A” experiences an electrical malfunction.
Example of a transmission pressure control solenoid:
What is the severity of this DTC?
Initially, the severity of this code is moderate, but if not addressed promptly, it can escalate to a more severe level.
What are some of the symptoms of the code?
Symptoms of a P0748 trouble code may include:
What are some of the common causes of the code?
Possible causes for this P0748 transmission code may include:
What are some P0748 troubleshooting steps?
Prior to starting the troubleshooting process for any malfunction, it is advisable to research the Technical Service Bulletins (TSB’s) specific to the vehicle’s year, model, and transmission. In some cases, this can save a significant amount of time by providing guidance in the right direction. It is also recommended to check the vehicle records to determine the last time the filter and fluid were changed, if possible.
Fluid & Wiring Inspections
The first step is to check the fluid level and examine the condition of the fluid for any contamination. Before changing the fluid, it is important to check the vehicle records to verify the last time the filter and fluid were changed.
Next, perform a detailed visual inspection to check the condition of the wiring for any obvious defects. Inspect the connectors and connections for security, corrosion, and damaged pins. This should include all wiring and connectors related to the transmission pressure control solenoids, transmission pump, and PCM. Depending on the configuration, the transmission pump may be electrically driven or mechanically driven.
Advanced Steps
The advanced steps are highly specific to the vehicle and require specialized equipment for accurate execution. These procedures necessitate the use of a digital multimeter and the specific technical references for the vehicle. It is important to obtain the specific troubleshooting guidelines for the vehicle before proceeding with the advanced steps. Voltage requirements may vary depending on the specific model of the vehicle. Fluid pressure requirements will also vary based on the transmission design and configuration.
Continuity Checks
Unless otherwise specified by the technical data, the normal readings for wiring and connections should be 0 ohms of resistance. Continuity checks should always be performed with the power removed from the circuit to avoid shorting the circuit and causing further damage. Resistance or lack of continuity indicates faulty wiring that is either open or shorted and must be repaired or replaced.
What are some common repairs for this code?
Possible misdiagnosis may include:
We always recommend seeking professional mechanical service to resolve this issue. However, if that is not possible, we offer the option to permanently delete this specific DTC. All other codes will continue to be addressed. If you are interested in this option, please upload your ECU file to our portal.
