P07BB: Transmission Park Position Sensor/Switch B Circuit Performance/Low

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. P07BB means sensor B reads in the band between its 'released' and 'pressed' zones (53.2–73.7 % of 5 V, ICCM 45–58 %), checked only when P07B9/P07BA are not set, after two trips. GM's 2017 bulletin also lists it for a knob not fully seated or a connector not latched. No other manufacturer is documented.

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

• P button sensor faulty or worn
• Knob not seated, button sticking
• Contact resistance in the connector
• Module software

What to check, in order

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

1. Check the fluid level and condition
2. With the connector unplugged, check whether the signal wire is making contact with ground.
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 P07BB means

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

Frequently asked questions

Can I keep driving with code P07BB?

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

What causes code P07BB?

The most common causes are: p button sensor faulty or worn; knob not seated, button sticking; contact resistance in the connector.

Related codes

• P07BCTransmission Park Position Sensor/Switch B Circuit Performance High
• 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
• P07BETransmission Park Position Sensor/Switch A/B Correlation

Sources

• gsi.ext.gm.com: 19OBDG03D Diagnostics
• gsi.ext.gm.com: 19OBDG03B Diagnostics
• gsi.ext.gm.com: 23OBDG03A Part2
• static.nhtsa.gov: MC 10116541 9999

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.