The P0991 OBD-II code indicates a problem with the Transmission Fluid Pressure Sensor/Switch “E” circuit. This code is triggered when the engine’s control module (PCM) or the Transmission Control Module (TCM) detects an intermittent issue with the fluid pressure sensor or its electrical circuit.
What Does the P0991 Code Mean?
The P0991 code means that there is an intermittent issue with the Transmission Fluid Pressure Sensor/Switch “E” circuit. This sensor plays a crucial role in helping the PCM or TCM manage the hydraulic fluid used to engage the clutches in the transmission, facilitating smooth shifting.
What Causes the P0991 Code?
Several factors can trigger the P0991 code, including:
- Transmission Control Module (TCM) failure
- Low transmission fluid level
- Transmission fluid pressure sensor failure
- Wiring issues within the circuit
What Are the Symptoms of the P0991 Code?
Common symptoms associated with the P0991 code include:
- Transmission may not shift properly
- Increased fuel consumption
How Serious Is the P0991 Code?
The P0991 code is considered urgent and may lead to significant malfunctions, potentially causing severe damage to the vehicle. It is important to address this issue promptly to avoid compromising the safety and performance of your vehicle.
How to Diagnose the P0991 Code
To diagnose the P0991 code, a mechanic will typically follow these steps:
- Use an OBD-II scanner to confirm the P0991 code and check for any related codes.
- Inspect the transmission fluid level and condition.
- Examine the wiring and connectors associated with the Transmission Fluid Pressure Sensor.
- Test the Transmission Fluid Pressure Sensor for proper function.
- Check the TCM for any faults or failures.
Common Repairs for the P0991 Code
Common repairs for the P0991 code may include:
- Replacing a faulty Transmission Fluid Pressure Sensor
- Repairing or replacing damaged wiring or connectors
- Refilling or replacing low or contaminated transmission fluid
- Replacing a malfunctioning Transmission Control Module (TCM)
How Much Does It Cost to Fix the P0991 Code?
The cost to fix the P0991 code can vary widely based on the root cause of the problem. Simple repairs, like replacing a sensor or fixing wiring issues, may cost between $100 to $300. However, if the TCM needs to be replaced, the cost could range from $500 to $1,500 or more, depending on the vehicle model and labor costs.
Can I Fix the P0991 Code Myself?
If you have experience with automotive repairs and the necessary tools, you may be able to diagnose and fix the P0991 code yourself. However, it is crucial to understand the complete diagnostic routine and ensure all underlying issues are addressed. If you’re uncertain, it is always best to consult with a professional mechanic to avoid unnecessary repairs.
