Code Definition

P1890 — Throttle Position signal input

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

About P1890

P1890 is a manufacturer-specific powertrain diagnostic trouble code recorded for GM vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

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

The Transmission Control Module relies on a throttle position signal to schedule shift points, control line pressure, and manage torque during shifts. On these GM systems the TCM does not read the throttle sensor directly but receives the throttle position value from the Engine Control Module over the serial data bus, such as Class 2 or CAN. DTC P1890 sets when the TCM receives a throttle position value that is missing, out of range, or implausible compared with other data, or when the signal integrity is lost. The result is usually altered shift behaviour, since the transmission loses the thr...

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