Transmission Fluid Pressure Sensor Circuit Low
The P0842 code indicates that the transmission control module (TCM) has detected a low voltage signal from the transmission fluid pressure (TFP) sensor or switch circuit. This sensor monitors hydraulic pressure inside the transmission to ensure proper shifting. A low circuit condition can be caused by a faulty sensor, damaged wiring, low transmission fluid, or internal transmission issues. This can lead to harsh shifting, slipping, or limp mode.
01. Most Common Causes
- Faulty transmission fluid pressure sensor
- Damaged or corroded wiring/connectors in the sensor circuit
- Low or contaminated transmission fluid
- Internal transmission mechanical failure
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or delayed shifting
- Transmission slipping or overheating
- Vehicle enters limp mode
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
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 pins.
Step 4: Test the sensor voltage and resistance with a multimeter; compare to manufacturer specs.
Step 5: If sensor and wiring are okay, perform a transmission pressure test to rule out internal issues.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as low transmission pressure can cause internal damage. If the vehicle is shifting poorly or in limp mode, have it towed to a shop.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Replacing the sensor can range from $100-$300 including parts and labor. If internal transmission repairs are needed, costs can exceed $1,000.