P2B98Exhaust Pressure Control Valve A Supply Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2B98 says the motor of exhaust pressure control valve A is not getting enough supply voltage. On GM's 3.0-litre Duramax, whose 2025 table 25OBDG04B documents the code, the H-bridge that drives the exhaust flap reports undervoltage below 6 V; 240 failed out of 300 samples taken every 12.5 ms set it, outside cranking and with the powertrain relay delivering more than 11 V. Type A, MIL after one trip. Because the main relay is fine in that case, the loss lies further on: a fuse, the feed wire, the connector or a weak ground of the driver. GM bulletin 21-NA-149 lists P2B98 among codes that chafed engine harnesses and blown fuses caused on 2019–2021 trucks, the 3.0 l LM2 included. Without power the flap stays put, so warm-up and back-pressure control suffer. P2B99 is the overheating driver.
- What you may notice
- Check engine light after one drive
- Exhaust flap without function, slower warm-up
- Further codes for the same fuse or harness
- Likely causes
- LikelyBlown fuse or interrupted feed to the valve actuator
- PossibleEngine harness chafed and shorted (GM 21-NA-149)
- PossibleCorroded connector or poor ground at the actuator
- RareWeak battery or charging fault causing voltage dips
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €30 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.