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Home / DTC / P1158 — Fuel Trim Adaptation Additive Bank 1 Low

P1158 — Fuel Trim Adaptation Additive Bank 1 Low

Detailed page for trouble code P1158.

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Code

P1158

BMW P — Powertrain

Fuel Trim Adaptation Additive Bank 1 Low

Brand: BMW
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Intake air leak (vacuum, intake boot, manifold gasket)
  • Contaminated or failed mass air flow (MAF) sensor
  • Faulty oxygen (lambda) sensor or heater circuit on Bank 1
  • Low fuel pressure or failing fuel pump/regulator
  • Leaking or clogged fuel injector(s) on Bank 1
  • Wiring/connectors or ECU software/parameter issue

Symptoms

  • Check Engine Light / MIL on
  • Rough idle or intermittent stumbling
  • Poor throttle response or reduced performance
  • Reduced fuel economy
  • Elevated or fluctuating CO/HC emissions
  • Possible hard starting under some conditions

What to check

  • Read and record stored freeze frame and all related codes
  • Scan live data: STFT and LTFT (additive) for Bank 1 and Bank 2
  • Monitor upstream oxygen sensor voltages/lambda and heater status
  • Check MAF sensor raw output (g/s) and intake air temp readings
  • Verify fuel rail pressure and fuel pump operation
  • Visually inspect intake tract, vacuum lines, and PCV hoses; perform smoke test

Signal parameters

  • Long Term Fuel Trim (LTFT) Bank 1 (additive)
  • Short Term Fuel Trim (STFT) Bank 1
  • Upstream O2 sensor voltage / lambda Bank 1
  • MAF: mass air flow (g/s) and frequency
  • Fuel rail pressure (bar/psi)
  • Injector pulse width / duty cycle Bank 1

Diagnostic algorithm

  1. Retrieve all DTCs and freeze frame data. Note conditions when code set (load, temp, RPM, fuel trim values).
  2. Clear codes and perform a controlled test drive while monitoring STFT/LTFT, MAF, O2 sensors and fuel pressure to reproduce the fault.
  3. Visually inspect intake tract, intake manifold gasket, vacuum lines, PCV and turbo inlet/outlet boots for cracks, loose clamps or leaks. Use a smoke test if needed.
  4. Check MAF sensor operation and cleanliness. Clean MAF with approved cleaner or substitute with known-good sensor if suspect.
  5. Measure fuel rail pressure at key-on and engine running; compare to manufacturer spec. Test fuel pump supply and pressure regulator.
  6. Monitor upstream O2 sensor waveform for proper switching and response; check heater circuit resistance/voltage. Replace sensor if out of spec or slow.
  7. Inspect injector wiring and measure injector current/pulse width. Perform balance or flow test on Bank 1 injectors if suspect.
  8. Inspect wiring/connectors to sensors and ECU for corrosion, damage or poor grounds. Repair as needed.
  9. If no mechanical fault found, check for ECM software updates or calibration issues; perform adaptation reset/relearn per BMW procedure and retest.
  10. After repairs, clear codes and verify that LTFT/additive values return to acceptable range and that MIL does not return.

Likely causes

  • Intake tract vacuum leak or cracked intake boot
  • MAF sensor contamination/incorrect reading
  • Faulty oxygen sensor providing incorrect feedback
  • Low fuel pressure (weak pump, clogged filter, regulator issue)
  • Wiring or connector corrosion at sensors on Bank 1

Fault status

⚠️ Status
Fuel trim adaptation for Bank 1 is below expected range; engine control has flagged a fuel trim adaptation fault affecting mixture control for bank 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

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