Code Definition

P1890 — Transmission 4WD Mode Select Return Input Circuit Failure

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

About P1890

P1890 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 P1890 is stored, the module has detected an electrical-circuit fault in the wiring, connector, or driver associated with the named component.

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.

P1890 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

This DTC is set when the transfer case control module detects an electrical fault in the four wheel drive mode select switch return input circuit. The return input provides feedback on the position of the mode selector, such as two wheel drive, four wheel drive high, and four wheel drive low. DTC P1890 sets when the return signal is missing, out of range, or inconsistent with the switch position for a calibrated time. As a result the module cannot reliably read the requested mode, so the selected mode may not engage and a warning light may illuminate.

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