Code
P1106
ALFA ROMEO
P — Powertrain
Boost pressure sensor fault
Views:
UK: 3
EN: 11
RU: 8
AI status
Completed
Completed
100%
Causes
- Failed or intermittent boost pressure (MAP) sensor
- Damaged or corroded sensor connector or wiring (open, short to ground or to 5V)
- Poor reference voltage or ground at the sensor
- Intake/vacuum/boost leak (intercooler, hoses, clamps)
- Faulty boost control solenoid, turbo actuator or wastegate causing unexpected boost
- ECU software/firmware error or ECU fault (less common)
Symptoms
- MIL/Check Engine Light on
- Reduced engine power or limp-home mode
- Poor acceleration under load or delayed boost
- Surging or unstable idle in some cases
- Increased fuel consumption or black smoke under load (diesel/turbocharged petrol)
- Hissing or audible boost leak
What to check
- Read freeze-frame and live data with a scan tool to confirm P1106 and operating conditions when the code set (RPM, load, temp, boost reading)
- Visual inspection of boost/MAP sensor, connector, and wiring for damage, corrosion or loose pins
- Check for proper 5V reference and ground at the sensor connector (key ON, engine OFF)
- Backprobe and measure sensor signal voltage at idle and while applying boost (compare to expected range)
- Perform smoke test or pressure check for intake/intercooler leaks and inspect vacuum hoses
- Verify operation of boost control solenoid and turbo actuator (apply/observe commanded changes and sensor reaction)
Signal parameters
- Reference supply: typically 5.0 V (key ON) — verify per vehicle spec
- Signal output (typical): approximately 0.5 V at high vacuum to ~4.5 V at high boost (sensor-specific; consult Alfa Romeo data)
- Pressure range: common MAP/boost sensors cover roughly -1.0 bar (vacuum) to +2.5–3.0 bar (relative boost); check exact spec
- Expected behavior: signal voltage should rise smoothly with increasing boost; no intermittent dropouts or fixed values
- Tolerance: deviations of >±0.2–0.5 V from expected values or open/short conditions may set the code
Diagnostic algorithm
- Connect a diagnostic scanner, read DTC(s) and freeze-frame data. Confirm P1106 is active or stored.
- Visually inspect MAP/boost sensor and wiring harness for damage, loose connectors, water intrusion or corrosion.
- With ignition ON, backprobe sensor connector: verify 5V reference present, good ground continuity, and measured signal voltage (engine OFF).
- Start engine and monitor live MAP/boost signal while revving gently. Signal should change smoothly from vacuum to boost range. Note any stuck, intermittent or out-of-range values.
- If reference or ground missing or incorrect, trace wiring, repair open/corroded connections and retest.
- If wiring and supply are good but signal is implausible, perform a smoke test or pressure test to find intake/boost leaks; repair leaks and retest.
- Test boost control components (solenoid, actuator, wastegate) to ensure commanded boost matches actual. Repair or replace faulty parts.
- If wiring and boost control check OK, bench-test or replace the MAP/boost sensor with OEM part and verify correct output.
- After repairs, clear codes and perform a road test under load to confirm the code does not return. If code returns with valid sensor and wiring, consider ECU/ software evaluation.
Likely causes
- Broken sensor harness / connector pins corroded
- Sensor output voltage stuck high or low (internal sensor failure)
- Loss of 5V reference or bad ground to sensor
- Large intake leak or stuck bypass valve producing implausible boost reading
- Failed boost control valve/solenoid preventing proper boost regulation
Fault status
Status
Boost pressure (MAP) sensor circuit fault — signal out of range or implausible compared with engine conditions.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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