P2BB9 code meaning
Engine Coolant Temperature Sensor 6 Circuit High
Powertrain system Generic code P2Bxx codes Check engine light
What P2BB9 means
A high signal from coolant sensor 6 corresponds to a resistance so large that only an interrupted circuit, a disconnected plug or a wire shorted to a voltage source explains it; read as temperature it would be colder than −60 °C. GM's tables check for this once the engine has run more than 10 s or intake air is warmer than −20 °C. For the sixth-sensor channel the limit is about 298 kΩ in the 2019 L3B/common edition (19OBDG03D) and about 174 kΩ in 2025 (25OBDG03B); 5 s of failures within 6 s give a Type B fault with the MIL on the second trip. As with P2B2E, GM's row names the radiator sensor while the low fault is tied to sensor 6. Bulletin 21-NA-149 lists P2BB9 for chafed harnesses on 2019–2021 pickups. The grounded counterpart is P2BB8.
P2BB9 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2BB9
- MIL on after the second trip
- Sensor 6 shows about −40 °C or lower
- Fans may run continuously
Common causes of P2BB9
- Most likelySensor 6 connector unplugged or not latched
- Most likelyBroken signal or ground wire, or signal shorted to voltage
- PossibleOpen sensor element
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Engine coolant temperature sensor 6Wiring harnessECM
What each part of P2BB9 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| B | Area: hybrid propulsion. |
| B9 | The exact fault in that area. |
What to do next
- Note P2BB9 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 P2BB9
What does P2BB9 mean?
P2BB9 means "Engine Coolant Temperature Sensor 6 Circuit High". A high signal from coolant sensor 6 corresponds to a resistance so large that only an interrupted circuit, a disconnected plug or a wire shorted to a voltage source explains it; read as temperature it would be colder than −60 °C. It is a generic code, so it means the same on every make.
Is it safe to drive with P2BB9?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P2BB9 fail an emissions test?
Yes, it can. P2BB9 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2BB9 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P2BB9 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.