P2398Diesel Intake Air Flow B Position Sensor Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2398 is logged when the position signal of the B intake throttle falls below its lower limit. Likely reasons are a signal lead shorted to ground, a lost 5 V supply, or a broken signal wire that the module input pulls low; on SENT sensors the transmitted raw value can also leave its range. No manufacturer documents P2398 itself. For the A valve, GM's LML reacts to less than 0.40 V persisting 5 s, its SENT-equipped 2017 diesels to under 1 % of 5 V in 200 of 250 checks (two trips), while Ford's 2023 diesels flag readings under 0.08 V lasting 3 s. If several 5 V sensors fail at once, suspect a shorted shared reference circuit. The flap is normally switched off, leaving the EGR loop with less control.
- What you may notice
- MIL on
- Further 5 V sensor codes at the same time
- Regeneration suspended
- Likely causes
- LikelySignal wire shorted to ground
- PossibleOpen 5 V reference or open signal wire
- PossibleShared 5 V reference pulled down by another faulty sensor
- RareInternally failed position sensor
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €30 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.