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Home / DTC / P1176 — Mixture 2 strength (additive) fault

P1176 — Mixture 2 strength (additive) fault

Detailed page for trouble code P1176.

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Code

P1176

ALFA ROMEO P — Powertrain

Mixture 2 strength (additive) fault

Brand: ALFA ROMEO
Type: P — Powertrain
AI status
Completed
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Page language: EN

Causes

  • Failed additive dosing pump or metering unit
  • Additive concentration sensor (dosage sensor) faulty or out of calibration
  • Clogged or leaking additive injector/nozzle
  • Low or contaminated additive in tank
  • Wiring harness fault: open, short to ground or intermittent connector
  • Corroded or loose electrical connectors

Symptoms

  • Malfunction Indicator Lamp (MIL) / Check Engine light illuminated
  • Additive or emission system warning message on dash
  • Poor drivability under load or after cold start
  • Higher than normal emissions, possible failed emissions test
  • Possible rough idle or hesitation
  • Reduced fuel economy in some cases

What to check

  • Read/record freeze frame and full DTC list with a capable scan tool
  • Confirm vehicle manufacturer-specific description of P1176 and related pending codes
  • Check additive tank level and inspect for contamination or foreign debris
  • Visually inspect wiring harness and connectors for damage, corrosion or poor connection at additive pump/sensor and ECU
  • Perform continuity and resistance checks on pump and sensor circuits (compare to manufacturer specs)
  • Command additive pump/sensor with diagnostic tool (if supported) and watch for correct operation

Signal parameters

  • Additive sensor output voltage: typically within a narrow expected range — consult manufacturer specs (example ranges commonly 0.5–4.5 V depending on sensor type)
  • Sensor resistance: check service manual for expected ohms; open/short indicates fault
  • Pump current draw: compare measured amp draw to spec when commanded (excessive or zero draw indicates mechanical/electrical fault)
  • Command duty cycle or on/off status from ECU: should change when commanded by diagnostics
  • Injector/nozzle pulse width: present on some systems when additive is metered; confirm pulse activity during dosing

Diagnostic algorithm

  1. Retrieve and record DTCs and freeze-frame data with a full-function scan tool. Check for related codes (fuel trims, O2 sensors, other additive related codes).
  2. Verify additive tank level and visually inspect additive for contamination, crystallization or water ingress; top up with correct additive if required.
  3. Visually inspect wiring and connectors at additive pump, sensor and ECU for damage, corrosion, or poor seating. Repair any damaged wiring or connectors.
  4. With connector disconnected, measure sensor resistance/voltage at harness side and compare to service data. Reconnect and measure while commanding system if possible.
  5. Command the additive pump using the scan tool and observe pump operation and current draw. If pump does not run or draws excessive current, remove and bench-test/replace pump.
  6. Check additive feed lines, filters and dosing injector/nozzle for blockages; clean or replace as required.
  7. If sensor readings are out of spec while wiring and pump are known good, replace the additive concentration sensor.
  8. After component repair or replacement, clear codes, re-learn any required adaptations per manufacturer procedure, and perform a test drive including conditions that previously set the code. Re-scan to ensure code does not return.
  9. If problem persists and wiring/power/GND are good, consider ECU diagnostic reflash or replacement per manufacturer guidance.

Likely causes

  • Additive dosing pump electrical failure or stuck mechanical parts
  • Additive concentration sensor producing incorrect voltage or resistance
  • Blocked additive feed line or injector nozzle
  • Low additive level or contaminated additive tank
  • Damaged connector or pin corrosion in sensor/pump circuit

Fault status

⚠️ Status
ECU reports additive/mixture strength for bank 2 outside expected range; control has set a fault and illuminated the MIL. Related emission control strategies may be limited until fault is resolved.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

Similar codes

P1175 P1177 P0172 P0175 P2196 P0191
89

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