BMW 320i Prins LPG P1100 P1101 Fault Codes After Service – Airflow and Pressure Issues

User question

bmw 320i lpg lli aracım devamlı p1100 p1101 hatası veriyyor oto gaz prinns marka llpg servisine gittim çıkınca 10 km gitmeden p 110 p1101 hata sı veriyor lpg basınç ayarı ile ilgilimidir

Artificial Intelligence Response

Direct answer to the question

• Short answer: Yes—an incorrect or unstable LPG pressure and/or poor LPG calibration can indirectly trigger P1100–P1101, but on BMW 320i (E90/N46) these codes most commonly point to a MAF/air‑intake plausibility problem. Verify the engine is fault‑free on gasoline first, then correct LPG pressure stability and mapping.
• Key points:
  • P1100/P1101 are “airflow plausibility/out‑of‑range” faults (MAF vs. modeled airflow).
  • Vacuum leaks, dirty/failing MAF, throttle body adaptation, or wiring can cause them.
  • LPG that runs lean/rich due to pressure drop/spikes or mis‑mapping will push fuel trims to limits and set these codes shortly after driving.

Detailed problem analysis

• What the DME is flagging:
  • The BMW DME (DME MSV70/MSV80 family on N46) continuously cross‑checks MAF signal against throttle angle, RPM, MAP, lambda feedback and learned fuel trims. If measured airflow or the correction needed to keep lambda ≈1 is outside the self‑test window, it stores P1100/P1101.
• Why it happens “10 km after leaving service”:
  • Many OBD monitors only complete under steady cruise after closed‑loop learning (typically a few minutes of driving). As soon as trims drift beyond limits (e.g., LTFT > ~+15% or STFT swings), the codes set—hence the repeatable fault within a short distance.
• How LPG contributes:
  • If reducer pressure sags at load, injectors can’t deliver commanded fuel → mixture goes lean → trims climb → airflow plausibility fails.
  • If pressure is too high or injectors oversized, mixture goes rich at certain load cells → trims go negative → plausibility fails.
  • MAP/temperature sensor placement/calibration errors in the LPG kit distort gas density compensation, causing load‑dependent mixture errors even with “correct” static pressure.

Current information and trends

• Field experience and current community resources consistently tie P1100/P1101 on N46 to MAF/air‑intake plausibility and frequently report recurrence on LPG‑converted cars if the gasoline side isn’t perfect or the LPG map is not road‑tuned.
• Best practice in 2024–2026 LPG tuning circles: closed‑loop, road‑load calibration using live trims and lambda on gasoline first, then mirroring those results on LPG with stable rail pressure and per‑RPM/load correction maps. Pressure stability under transient load is emphasized more than just “a fixed setpoint.”

Supporting explanations and details

• Typical healthy figures for a 2.0L N46 (guideline values, warm engine, sea level):
  • MAF at hot idle: roughly 2–4 g/s; at 2500 rpm no‑load: roughly 8–12 g/s.
  • Fuel trims: STFT within about ±5%, LTFT within about ±8% on gasoline. On LPG, match these as closely as possible; persistent deviations indicate mapping/pressure issues.
• LPG pressure behavior criteria (generic, reducer‑dependent):
  • At steady cruise and moderate load, rail pressure should be stable (variation typically within ±0.05–0.10 bar).
  • Wide‑open throttle shouldn’t show a transient drop greater than ~0.2 bar; if it does, look for clogged filters, weak reducer, low coolant heat transfer, or undersized lines.
• Why “throttle body cleaning/adaptation” sometimes helps:
  • Carbon on the throttle and unlearned stops alter modeled airflow; after cleaning, perform DME throttle adaptation reset so the internal model matches reality.
• Why vacuum leaks are critical on N46:
  • Crankcase ventilation (CCV/PCV) hoses, intake boots, DISA seal, and small vacuum lines commonly harden/crack. Any unmetered air after the MAF will create the same plausibility error the LPG then amplifies.

Ethical and legal aspects

• Safety: Work on LPG only with the tank valve closed, engine off, and in a ventilated area; no sparks or open flames. Depressurize the rail before opening any fittings.
• Emissions: Do not defeat OBD monitors or lambda feedback. Repairs should restore proper closed‑loop operation on both fuels to protect the catalyst.

Practical guidelines

1. Isolate the fault
   • Switch LPG off (force gasoline only), clear codes, and drive 50–100 km.
   • If P1100/P1101 return on gasoline: fix the gasoline side first (MAF/intake/Throttle/CCV/wiring). If they do not return on gasoline but do on LPG: focus on LPG pressure and mapping.
2. Gasoline‑side baseline (must be perfect before LPG tuning)
   • Inspect/clean or replace the MAF with an OE‑quality unit if readings are erratic.
   • Smoke‑test the intake for leaks (airbox to head, including CCV and DISA).
   • Clean throttle body; then perform throttle adaptation reset (ISTA/INPA).
   • Verify O2 sensor operation and trims under idle/cruise/load.
3. LPG‑specific checks (Prins)
   • Log live data: gas rail pressure, gas temp, MAP, injector pulse, STFT/LTFT while driving (idle, 2000–3000 rpm steady, uphill load, WOT).
   • If pressure dips at load: check/replace LPG filters, verify reducer coolant flow/temperature, check reducer diaphragm, line restrictions, and injector rail size.
   • Verify MAP/temperature sensor placement (sample from common plenum, no dead legs) and correct sensor calibration in software.
   • Perform a proper road calibration: adjust the LPG map so trims on LPG mirror gasoline trims across the load/rpm grid. Avoid relying on idle/neutral revs only.
4. Wiring and grounds
   • Inspect MAF harness for chafing, corrosion, poor grounds. Verify 12 V/5 V reference and signal with a scope if available to catch intermittent dropouts that only appear on vibration/load.
5. Acceptance test
   • After each change, clear adaptations and codes, drive through the monitor conditions, and confirm trims and MAF plausibility remain normal for at least one full drive cycle without returning faults.

Possible disclaimers or additional notes

• “Correct” LPG pressure setpoints vary by reducer/injector family—always use the Prins documentation for your exact kit. Focus on stability under load rather than a single static number.
• Some aftermarket MAFs read systematically off; if in doubt, borrow a known‑good OE MAF for A/B testing.

Suggestions for further research

• Prins service manual for your exact system (reducer/injector type) for pressure specs and sensor calibration.
• BMW ISTA service procedures for N46: throttle adaptation, smoke test points, and MAF diagnostics.
• Case studies of N46 with LPG for typical vacuum‑leak locations and successful trim targets.

Brief summary

• Your recurring P1100/P1101 are airflow plausibility faults. LPG pressure that is mis‑set or unstable will aggravate trims and can trigger these codes, but the root cause is often on the gasoline/air‑intake side (MAF, vacuum leaks, throttle adaptation). First prove the engine is clean on gasoline, then stabilize and road‑tune the Prins system with live‑data logging (pressure, trims, lambda). If you’d like, share a short log (idle, cruise, uphill) of MAF g/s, MAP, gas pressure, STFT/LTFT on gasoline and on LPG—I can pinpoint the failing step.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.