Technical Description of OBD-II Trouble Code
Intermittent Issue with Pressure Control Solenoid A
What does that signify?
This is a standard diagnostic trouble code (DTC) for transmissions and is commonly found in OBD-II vehicles with automatic transmissions.
This can apply to various vehicle brands such as Ford, Mercury, Lincoln, Jaguar, Chevrolet, Toyota, Nissan, Allison/Duramax, Dodge, Jeep, Honda, Acura, etc. While it is a generic code, the specific repair steps may differ depending on the year, make, model, and powertrain configuration.
When the P0749 OBD-II trouble code is triggered, it means that the Powertrain Control Module (PCM) has detected an issue with the Transmission Pressure Control Solenoid “A”. Most automatic transmissions have three solenoids, namely solenoid A, B, and C. The trouble codes associated with the “A” solenoid are 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 relies on bands and clutches that change gears by ensuring the fluid pressure is in the correct place at the right 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 appropriate time.
The P0749 code is triggered when the Pressure Control Solenoid “A” operates intermittently.
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?
Some symptoms of a P0749 trouble code may include:
What are some of the common causes of the code?
Possible causes for this P0749 transmission code may include:
What are some P0749 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. This can save a significant amount of time by providing guidance in the right direction. If possible, check the vehicle records to confirm when the filter and fluid were last changed.
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, verify the vehicle records to determine when the filter and fluid were last changed.
Next, conduct 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 or mechanically driven.
Advanced Steps
The advanced steps are highly vehicle-specific and require specialized equipment for accurate execution. These procedures necessitate the use of a digital multimeter and specific technical references for the vehicle. Obtain the specific troubleshooting guidelines for your vehicle before proceeding with the advanced steps. Voltage requirements may vary depending on the specific vehicle model. Fluid pressure requirements will also differ 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 misdiagnoses may include:
We hope that the information provided in this article has been helpful in guiding you towards resolving the issue with your pressure control solenoid trouble code. However, please note that this article is purely informational, and the specific technical data and service bulletins for your vehicle should always take precedence.
