Code Definition

P0891 — TCM Power Relay Sense Circuit High

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0891

P0891 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0891 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.

Because P0891 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The fault code P0891 is activated when the control module detects a high signal in the Transmission Control Module (TCM) power relay sense circuit. This high signal condition indicates that the voltage in the sense circuit, which is responsible for monitoring the status of the TCM power relay, exceeds the upper limit of the normal operational range. A high signal could suggest an issue with the relay's function or a fault in the circuitry, potentially impacting the accurate monitoring of power relay status and thereby affecting the TCM's operation and transmission control.

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