Powertrain
generic / SAE
P0840
Transmission Fluid Pressure Sensor/Switch A Circuit Range/Performance
The transmission fluid pressure sensor A reading is implausible compared to commanded line pressure. The TCM detects sensor drift or hydraulic leakage.
SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number8 / 40
Possible causes
- Pressure sensor drift high
- Internal hydraulic leak medium
- Sensor element aged beyond calibration window low
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Inspection / repair
- Difficulty: hard
- DIY: shop recommended
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References
sae:J2012