P0842 means the pressure sensor or switch A circuit is reading low. That can mean low actual pressure, a bad sensor, a wiring problem, or a circuit that is shorted or pulled down.
P0842 Versus P0841
P0841 says the signal is out of the expected range. P0842 is more specific: the signal is too low. That narrows the test path, but it still does not prove whether the pressure itself is low or the electrical signal is wrong.
Common Causes
- Failed pressure sensor or switch.
- Shorted wiring or connector corrosion.
- Low fluid level or aerated fluid.
- Restricted filter or pressure loss.
- Valve-body or internal leakage.
Symptoms
The vehicle may shift harshly, slip, delay engagement, go into limp mode, or only show a warning light. If the symptom changes hot versus cold, that detail helps separate electrical signal trouble from a real hydraulic issue.
Diagnosis
We inspect wiring and connector condition, compare pressure sensor voltage to scan data, check fluid and pan evidence, and look for companion pressure or ratio codes. If the sensor signal is low but the transmission behaves normally, the circuit is suspect. If the vehicle slips, pressure loss may be real.
Repair Path
A P0842 repair may stay small if it is a sensor or harness fault. If low pressure is confirmed, the repair can involve the valve body, pump, filter, seals, or internal clutches.
