Code Definition

P1804 — Transmission 4-Wheel Drive High Indicator Circuit Failure

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Generic

About P1804

P1804 is a manufacturer-specific powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1804 is stored, the module has detected a signal or supply voltage higher than the expected operating range.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1804 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The powertrain control module (PCM) or transfer case control module (TCCM) sets P1804 when it detects an issue in the 4WD High indicator circuit. This circuit is responsible for signalling when the vehicle is engaged in 4WD High mode. A failure may indicate an open, short, or unexpected voltage condition in the circuit.

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