Transmission Fluid Pressure Sensor Circuit Intermittent
The P0844 code indicates that the powertrain control module (PCM) has detected an intermittent signal from the transmission fluid pressure (TFP) sensor or switch. This sensor monitors hydraulic pressure inside the transmission to ensure proper shift timing and line pressure. An intermittent circuit issue can cause erratic transmission behavior, such as harsh or delayed shifts, and may lead to transmission damage if ignored.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or erratic shifting
- Transmission slipping or delayed engagement
- Reduced fuel economy
2. Most Common Causes
- Faulty transmission fluid pressure sensor/switch 'A' (intermittent internal failure)
- Damaged, chafed, or corroded wiring in the signal, 5V reference, or ground circuit
- Loose, corroded, or poorly retained connectors at the sensor or TCM/PCM
- Low or contaminated transmission fluid causing actual pressure fluctuations
- Internal TCM/PCM failure (uncommon)
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data to capture conditions when the fault occurred.
Step 2: Inspect transmission fluid level and condition; top off or replace if necessary.
Step 3: Visually check the TFP sensor wiring and connector for damage, corrosion, or loose connections.
Step 4: Use a multimeter to test the sensor's resistance and voltage output per manufacturer specifications.
Step 5: If wiring and fluid are okay, replace the TFP sensor and clear codes; test drive to verify repair.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive for extended periods, as intermittent pressure readings can cause transmission damage. You may experience harsh shifts or slipping, which can worsen over time.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on the vehicle and shop rates. The sensor itself is often inexpensive, but labor may vary.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.