P07B9 code meaning
Transmission Park Position Sensor/Switch B Circuit Low
Powertrain system Generic code P07xx codes Check engine light
What P07B9 means
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. P07B9 is the same check as P07B3 for sensor B: below 446 counts (43.6 % of 5 V) in GM's selector modules, below 35 % in the ICCM, 115 or less in the 2025 diesel engine module, after two trips. A short to ground or an open supply is typical.
P07B9 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P07B9
- 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
Common causes of P07B9
- Most likelySignal shorted to ground or supply wire open
- PossibleSelector knob not fully seated or connector not latched
- PossibleSensor in the P button faulty
- Less likelySelector or control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Park position sensorElectronic range selectorSensor wiringTransmission control module
What each part of P07B9 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 7 | Area: transmission. |
| B9 | The exact fault in that area. |
What to do next
- Note P07B9 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P07B9
What does P07B9 mean?
P07B9 means "Transmission Park Position Sensor/Switch B Circuit Low". With electronic gear selection the park position sensor/switch reports the park request or position. It is a generic code, so it means the same on every make.
Is it safe to drive with P07B9?
Drive gently and only to a workshop. With P07B9 the car can go into limp mode (reduced power) to protect itself.
Will P07B9 fail an emissions test?
P07B9 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P07B9 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P07B9 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.