P1571

Code

MINI P — Powertrain

Engine control module (ECM), sensor supply circuit A - high output

Brand: MINI

Type: P — Powertrain

Views: UK: 1 EN: 4 RU: 0

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Page language: EN

Internal ECM voltage regulator failure
Wiring short to battery/ignition feed on the sensor supply circuit
Aftermarket device or modification feeding the sensor supply rail
Faulty connector or pin damage causing cross-connection with a high-voltage circuit
Poor or missing ground that changes reference behavior
Intermittent harness damage (chafing, corrosion)

Malfunction Indicator Lamp (MIL/Check Engine) illuminated
Stored/active P1571 code (may appear with other codes)
Erratic or out-of-spec sensor voltages (e.g., temperature, pressure, throttle)
Reduced drivability, limp-home behavior or degraded performance if ECM limits functions
Possible no-start or hard-start in extreme cases

Read and record all stored codes and freeze-frame data with a compatible scanner
Visually inspect wiring harnesses and connectors related to sensor supply A for damage, corrosion, or pin push-out
Check for aftermarket accessories spliced into engine harness near sensor power rail
Measure battery voltage (engine off and running) to confirm nominal system voltage
Measure the sensor supply A voltage at the ECM harness connector (with ignition ON, engine OFF) and at representative sensors
Perform a continuity/short-to-power test from the sensor supply circuit to battery positive and to other power circuits

Sensor supply A (ECM reference) target ≈ 5.0 V (typical range 4.75–5.25 V) — verify vehicle-specific spec
Battery voltage (engine off) ≈ 12.4–12.8 V; running ≈ 13.5–14.8 V
If supply measures significantly above spec (e.g., near battery voltage or >5.5 V) suspect short to battery or ECM regulator fault
When sensors disconnected the reference may change — measure both at ECM connector and at sensors

Connect a diagnostic scanner, retrieve P1571 and any related codes, record freeze-frame and operating conditions.
Visually inspect connectors and wiring for sensor supply A for damage, corrosion, aftermarket taps, or pinback/bridging.
With ignition ON (engine OFF) measure voltage at the ECM sensor supply A pin and at a representative sensor power pin. Compare to manufacturer specification (≈5 V).
If voltage is high at ECM connector, suspect ECM internal regulator — verify grounding and battery voltage, then consult OEM test procedures before ECM replacement.
If voltage is normal at ECM but high at the sensor connector, inspect harness between ECM and sensor for a short to battery/another power source; perform back-probing and continuity/short tests.
Disconnect sensors on that supply rail and re-measure. If voltage returns to expected range when sensors disconnected, inspect each sensor for internal leakage or short to power.
Wiggle/torque test wiring while monitoring voltage to find intermittent faults.
Repair identified wiring or connector faults, then clear codes and road-test to confirm fault does not return.
If wiring/connector repairs do not correct the fault and ECM is confirmed as source by following OEM bench/ECM tests, replace or reprogram ECM per manufacturer procedure.

⚠️ Status

P1571 — ECM: Sensor supply circuit A high output (sensor reference voltage above expected range)

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

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P1571 — Engine control module (ECM), sensor supply circuit A - high output