P084E

What it means

P084E is a generic code meaning the powertrain control module or transmission control module has detected an intermittent fault in the circuit of transmission fluid pressure sensor or switch 'H'. The signal drops out, spikes or jumps to an implausible value and then returns to normal, rather than staying faulty. Which sensor or switch 'H' refers to, and where it sits, depends on the make, model and transmission, so check the manufacturer's data.

Symptoms

• Gearbox warning light or malfunction indicator lamp on
• Harsh, delayed or flared gear changes that come and go
• Transmission going into limp mode, often stuck in one gear
• Occasional loss of certain gears or no engagement for a moment
• Gear shifts that feel inconsistent, especially when the gearbox is hot or the car goes over bumps

Possible causes

• Damaged, chafed or corroded wiring to the pressure sensor or switch, with intermittent open circuit or shortlikely
• Loose, corroded or contaminated connector at the sensor, valve body or control unitlikely
• Faulty transmission fluid pressure sensor or switch giving an erratic signalpossible
• Transmission fluid leaking into the harness or connector, or fluid contaminated by debrispossible
• Low fluid level or aerated fluid causing unstable pressure readings, depending on the transmissionpossible
• Internal harness fault inside the transmission, or a fault in the valve body or solenoid assemblyrare
• Faulty control unit or an outdated calibration where the manufacturer has issued a known updaterare

How to diagnose

1. Read all stored and pending codes and the freeze frame data; note temperature, speed, gear and whether other pressure or solenoid codes are present
2. Check the transmission fluid level and condition (where a dipstick or check procedure is provided), looking for burnt smell, debris or foaming
3. Look for known issues and bulletins for the specific model and transmission, and identify which sensor is 'H' from the manufacturer's data
4. Inspect the wiring and connector for the sensor for chafing, heat damage, corrosion, fluid ingress and bent or pushed-back pins
5. With the engine running, wiggle the harness and connector while watching live pressure data or sensor status for dropouts
6. Check the sensor's reference voltage, ground and signal at the connector against specification, and test wiring continuity and insulation
7. Compare live pressure readings against expected values in different gears and temperatures
8. If the wiring is sound, test or substitute the sensor as the manufacturer's procedure allows, and check for any available calibration update

How to fix

• Repair or replace damaged wiring and fix any chafing at the source
• Clean, re-seat or replace corroded or loose connectors and terminals, and cure any fluid ingress
• Replace the faulty transmission fluid pressure sensor or switch
• Correct the fluid level or change the fluid and filter to the manufacturer's specification, and fix any leaks
• Repair the internal harness or valve body assembly if tests point to it
• Apply a manufacturer calibration update only where an outdated calibration is a documented cause

Can I keep driving?

Nearby codes

• P084DGenericTransmission Fluid Pressure Sensor/Switch H Circuit High
• P084FGenericPark/Neutral Switch Output Circuit