P2803: Transmission Range Sensor B Circuit High

What it means

Voltage on the range sensor B signal line is above the expected window. Wire shorted to B+ or sensor open.

At a glance

• Usually lights the check-engine light
• The engine or gearbox may go into limp mode

How it works

Range sensor B provides one of the transmission control unit’s selector-position signals. P2803 sets when that signal voltage is above the expected window, commonly because the wire is shorted to battery voltage or the sensor circuit is open.

Common causes

Most likely first.

1. Signal wire shorted to B+
2. Open range sensor B
3. Connector pins corroded - high contact resistance

Symptoms

• Check engine or transmission warning light on
• Harsh, delayed, or missing shifts
• Possible limp mode (locked in one gear)
• Slipping or shuddering during gear changes

How to diagnose it

1. Capture freeze-frame data and check live B-channel voltage or range status to confirm the signal is high when the fault sets.
2. Inspect the range sensor B connector and harness for a backed-out pin, corrosion, broken wire, or contact with a power feed.
3. Using the wiring diagram, check the B-channel signal for a short to battery voltage and verify the sensor’s supply and ground circuits.
4. Disconnect the sensor as directed by the manufacturer’s procedure and check whether the high signal remains on the harness side.
5. Test sensor B output and circuit continuity against the manufacturer’s specification before replacing the sensor.

Common fixes

• Reconnect a loose range sensor B plug or repair a backed-out terminal.
• Repair the B-channel wire shorted to battery voltage.
• Repair an open in the range sensor B circuit.
• Replace range sensor B if its output is high with a verified good harness and connections.

Can I keep driving?

Avoid driving if the range display is incorrect, shifting is erratic, or limp mode is active; the transmission may not know which range is selected. Stop if the selected range does not match the vehicle’s response.