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.

Likely causes

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

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, gsi.ext.gm.com.