The Transmission Control Module (TCM) has detected a voltage signal from the engine speed sensor circuit that exceeds the normal operating range. This typically indicates an open circuit or a sensor failure that prevents the TCM from accurately monitoring engine RPM.
The sensor has suffered an internal electrical failure, resulting in an open circuit or incorrect voltage output.
Chafed, broken, or severed wires between the sensor and the TCM are creating an open circuit.
Moisture or oxidation at the sensor or TCM plug is interrupting the signal flow.
An internal circuit failure within the Transmission Control Module is incorrectly processing the speed signal.
No, this is an electrical circuit code. It indicates a problem with how the speed is being reported to the computer, not a failure of the transmission gears or clutches.
No. It is very common to misdiagnose this as a TCM failure, but the issue is almost always a failed sensor or damaged wiring. The TCM should only be replaced after all wiring and sensors have been fully validated.
Low system voltage can sometimes cause erratic sensor readings, but a persistent 'Circuit High' code usually points to a hard electrical fault in the sensor circuit.