Powertrain, generic (extended)

P2B97 Exhaust Pressure Control Valve A Position Exceeded Learning Limit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2B97 concerns the electrically driven exhaust back-pressure flap of GM's 3.0-litre Duramax diesel. After key-off the module moves the flap to its fully closed and fully open stops and stores what the SENT position sensor reports there. GM's 2025 table 25OBDG04B flags a learned value outside its window: closed below 4.8 % or above 14.7 % of 5 V, wide open below 80 % or above 96.5 %, enabled with coolant 30–150 °C and at least 9.5 V; Type A, MIL after one trip, no debounce. GM preliminary information PIP5874B for 2023 Silverado/Sierra with the 3.0 l LZ0 restricts the replacement part and asks for a borescope look at flap travel and welding slag before the valve is changed. P2B98 and P2B99 cover supply and driver faults, P0476 the general function check.

Likely causes

Flap travel blocked by welding slag, soot or corrosion
Position sensor in the actuator drifted
Actuator gear or motor worn so the stops are not reached
Weak battery during the key-off learn

Symptoms

  • Check engine light after one drive
  • Slower warm-up or reduced exhaust heating for aftertreatment
  • Possibly reduced engine power

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–1,500
Time1–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

exhaust pressure control valve aexhaust pressure valve position sensor

Related codes

P2B98P2B99P0476P048BP047F

References: gsi.ext.gm.com, static.nhtsa.gov.