P2804 indicates an intermittent fault in the Transmission Range Sensor B circuit. This sensor reports the gear selector position to the transmission control module; when its signal fluctuates, the module may not know the correct gear. The result is often an illuminated check‑engine light, an erratic shift indicator, and possible starting or shifting problems.
Internal failure of the sensor can produce an intermittent signal, causing the circuit to drop or spike randomly.
Broken, chafed, or pinched wires in the sensor circuit can create intermittent opens or shorts, often due to age or heat exposure.
Oxidation or poor connection at the sensor or harness can cause voltage fluctuations that appear as intermittent faults.
If the sensor's ground path or 5 V reference is unstable, the signal can become erratic, especially under vibration.
A malfunction in the controller that processes the sensor input is possible but rare; it usually shows additional codes.
A mis‑adjusted shift lever or worn linkage can cause the sensor to read incorrectly, leading to intermittent circuit behavior.
No. While the PCM can be at fault, the majority of P2804 cases are due to a faulty sensor, damaged wiring, or poor connections. PCM replacement is rarely needed and is often a misdiagnosis.
The vehicle may still move, but you may experience erratic shifting, failure to start in Park, or a limp‑home mode. It is advisable to diagnose and repair the issue promptly to avoid transmission stress.
If the wiring, connectors, and voltages at the sensor are all within specification, and the fault persists after checking those, the sensor is the likely culprit.
A basic OBD‑II scanner, digital multimeter, and wiring diagram for the transmission range circuit are typically sufficient. An oscilloscope can help capture intermittent signals.