P1804: Transmission 4-Wheel Drive High Indicator Circuit Failure
MediumPowertrainTransmission
What does P1804 mean?
P1804 is a diagnostic trouble code indicating "Transmission 4-Wheel Drive High Indicator Circuit Failure". The ECU is reading a voltage that is above the expected range. This can be caused by a short to power in the wiring, a failed sensor, or a connector issue in the transmission.
Symptoms you may notice
- Check engine light (MIL) illuminated on dashboard
- Harsh or delayed gear shifts
- Transmission slipping
- Vehicle stuck in one gear (limp mode)
- Intermittent warning lights
Estimated repair cost
Typical range in Australia (parts + labour)
$300 – $3000 AUD
Common causes
- Damaged or corroded wiring harness
- Loose or disconnected electrical connector
- Failed transmission sensor or actuator
- Blown fuse in the related circuit
- Poor ground connection
What should you do?
This code sits in the exterior lighting. Nothing about how the car drives changes, but how easily other road users see you does, and a light out is an on-the-spot fine and an inspection failure. Worth sorting before you next drive at night.
Get a diagnosis for YOUR car
Code P1804 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.