P2B99Exhaust Pressure Control Valve A Driver Current/Temperature Too High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2B99 reports that the output stage driving exhaust pressure control valve A is running too hot or carrying too much current. In GM's 2025 diesel table 25OBDG04B for the 3.0-litre Duramax, the H-bridge driver temperature has to exceed 170 °C in 240 of 300 samples at 12.5 ms intervals, outside cranking and with more than 11 V on the powertrain relay; Type A, one trip. GM names internal faults of the valve motor as a typical cause, for example shorted windings or a flap that binds so the motor stalls under load. A harness short can overload the driver as well; bulletin 21-NA-149 lists P2B99 on 2019–2021 trucks with the 3.0 l LM2 and chafed engine wiring. The driver then usually shuts down to protect itself and the flap is left uncontrolled. P2B98 is the supply fault, P2B97 the learn fault.
- What you may notice
- Check engine light after one drive
- Exhaust flap no longer controlled
- Possibly reduced power or longer warm-up
- Likely causes
- LikelyValve motor with internal fault such as shorted windings
- PossibleFlap binding from soot or corrosion so the motor stalls
- PossibleShort in the actuator wiring (GM 21-NA-149)
- RareDefective driver stage in the control module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €1,800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.