P07B8: Transmission Park Position Sensor/Switch B Circuit/Open

With electronic gear selection the park position sensor/switch reports the park request or position. On GM's shift-by-wire selectors (2017 LaCrosse, XT4/XT5, Bolt EV, later SUVs and pickups) it is the P button, read by two redundant analog sensors A and B with separate 'released' and 'pressed' voltage zones. P07B8 means the circuit of the redundant sensor B is open. No manufacturer document available to us uses this code; GM covers an open analog circuit under its low and high codes (P07B9/P07BA). With one channel missing, the module can no longer cross-check the park request.

Symptoms

• Check engine light, 'service transmission' or 'unable to shift' message
• Park cannot be selected by button, or the car will not shift out of P
• P button illumination off

Most likely causes

• Wire or connector to the selector open
• Connector not latched
• Sensor faulty

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the fluid level and condition
2. Check the continuity of the wire between the component and the control module.
3. Read the input and output speed in live data
4. Check the connector and wiring
5. Check for other related engine codes
6. Consult the manufacturer's procedure for the transmission

Good to know

• Repair difficulty: medium
• It can trigger limp mode.

What each character of P07B8 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 7: Transmission
• B8: Specific fault in that system

Frequently asked questions

Can I keep driving with code P07B8?

Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.

What causes code P07B8?

The most common causes are: wire or connector to the selector open; connector not latched; sensor faulty.

Related codes

• P07B9Transmission Park Position Sensor/Switch B Circuit Low
• P07BATransmission Park Position Sensor/Switch B Circuit High
• P07BDTransmission Park Position Sensor/Switch B Circuit Intermittent/Erratic
• P07B2Transmission Park Position Sensor/Switch A Circuit/Open
• P07BETransmission Park Position Sensor/Switch A/B Correlation
• P0705Transmission Range Sensor A Circuit (PRNDL Input)

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 19OBDG03A Diagnostics

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.