P1108

Code

MINI P — Powertrain

Manifold absolute pressure (MAP) sensor - signal too low at full load for low engine speed

Brand: MINI

Type: P — Powertrain

Views: UK: 1 EN: 4 RU: 2

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Page language: EN

Causes

Failed or drifting MAP sensor
Short to ground or open in MAP sensor signal wiring or poor connector contact
Lost 5 V reference or poor sensor ground
Intake system restrictions (blocked intake, clogged air filter, closed throttle) producing abnormally low manifold pressure at full load
Large vacuum/boost leaks downstream of the sensor or between turbo and intake
ECU input circuit fault

Symptoms

Check Engine light (MIL) illuminated
Reduced engine power or limp-home mode under load at low RPM
Hesitation, stumbling or poor acceleration when accelerating from low RPM
Poor fuel economy, unstable idle or stalling in some cases
Possible additional codes related to fuel trim, boost control, or MAF

What to check

Read freeze-frame and live data (MAP, RPM, throttle position, MAF/airflow, commanded boost) with a scan tool and reproduce issue at low RPM/full-load.
Compare MAP reading to expected values for engine speed and throttle position; compare MAP vs calculated manifold pressure from MAF or load.
Visually inspect MAP sensor connector and wiring for damage, corrosion, pin push-out or water ingress.
Back-probe MAP sensor pins: verify 5 V reference (key ON), ground continuity, and sensor output voltage.
Perform a pressure/vacuum test of the intake: check for boost/vacuum leaks, collapsed hoses, restricted air filter or clogged intake path.
Unplug the MAP sensor and observe ECU reaction (some systems revert to default); use a hand vacuum/pressure pump to bench-test the sensor if available.

Signal parameters

Typical MAP sensor output: approx. 0.5–4.5 V for 0–100 kPa (manufacturer dependent). Output increases with manifold absolute pressure.
At full load/near-atmospheric pressure expect a high MAP voltage (close to the upper end of the sensor range) or near 100 kPa reading; at vacuum/idle the voltage is lower.
Expected live-data relationship: MAP should rise with throttle opening and correlate with MAF/engine load; a much lower-than-expected voltage at wide-open throttle/low RPM is abnormal.

Diagnostic algorithm

Connect a scan tool, record freeze-frame, and confirm P1108 is active or historic. Note RPM, throttle position, MAP value when the code set.
Reproduce the condition safely (low engine speed with heavy throttle) while monitoring live MAP, RPM, throttle position, MAF/airflow and commanded boost.
Visually inspect MAP sensor and intake/boost plumbing for damage, disconnected hoses, or restrictions.
With ignition ON (engine OFF) back-probe the MAP sensor connector: check for stable 5 V reference, ground continuity and that sensor output is within expected idle/atmospheric ranges. If no 5 V or no ground, trace harness to ECU.
With engine running, observe MAP voltage change as throttle is opened. If output does not rise toward expected values, suspect sensor or wiring short to ground.
Bench-test the sensor with a handheld vacuum/pressure pump if available: apply known pressures and verify sensor output follows the expected curve (compare to factory spec).
Perform a smoke or pressure test of the intake/boost system to locate leaks or restrictions that could cause incorrect manifold pressure under load.
Repair or replace failed components: secure/repair wiring and connectors, replace the MAP sensor if out of spec, repair intake leaks or restrictions. If wiring and sensor check good, consider ECU input circuit diagnosis.
Clear codes and road-test under the same conditions to confirm the fault does not return and that MAP behavior, fuel trims and drivability are restored.

Likely causes

Faulty MAP sensor
Damaged/loose wiring or corroded connector (signal, 5 V reference, ground)
Intake or boost plumbing leak or restriction
Failed sensor reference voltage or ground at ECU harness
Less likely: ECU fault

Fault status

⚠️ Status

P1108 — MAP sensor signal too low at full load/low engine speed. Check MAP sensor, wiring, reference/ground and intake/boost system for leaks or restrictions.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours

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P1108 — Manifold absolute pressure (MAP) sensor - signal too low at full load for low engine speed