P1572

Code

MINI P — Powertrain

Engine control module (ECM), sensor supply circuit A - noisy signal

Brand: MINI

Type: P — Powertrain

Views: UK: 1 EN: 2 RU: 1

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Page language: EN

Causes

Damaged or corroded wiring or connector on sensor supply (VREF) circuit A
Poor or high-resistance ground or battery negative connection
Faulty sensor drawing intermittent current or shorting to power/ground
ECM internal fault or bad VREF regulator inside the ECM
Excessive electrical noise from charging system or aftermarket accessories
Loose connector pins or poor contact at ECM or sensor connector

Symptoms

Check Engine Light (MIL) on, P1572 stored
Intermittent or erratic sensor readings (MAP, TPS, MAF, or other sensors on supply rail)
Rough idle, hesitation, or stalling
Reduced engine performance or limp-home mode
Poor fuel economy or surging
Codes from affected sensors (low/high input, implausible signal)

What to check

Read all stored codes and freeze frame data; note conditions when code set
Visual inspection of wiring harnesses and connectors for circuit A sensors for corrosion, pin damage, or water ingress
Check battery voltage and charging system for proper operation
Check engine and chassis grounds for corrosion, tightness, and low resistance
Backprobe sensor supply (VREF) at the ECM connector and at the sensors with key ON and engine running
Use an oscilloscope to look for noise/ripple on the sensor supply rail and on affected sensor signals

Signal parameters

Sensor reference supply (VREF) ≈ 5.0 V (key ON and engine running)
VREF stability: variation ideally < ±0.05 V under normal conditions
Allowed ripple/noise: typically < 0.1 V peak-to-peak on the reference rail
Sensor supply source impedance: low (typically < 100 Ω); high resistance indicates poor connection
Affected sensor signals should be steady and logical for the given operating condition (no bursts of high-frequency noise)

Diagnostic algorithm

Retrieve full DTC list, freeze frame and live data. Note which sensors are on 'circuit A' per vehicle wiring diagram.
Perform a visual inspection: connectors, pins, harness abrasion, signs of moisture or repairs along the sensor supply and ground paths.
Confirm battery & charging system health (battery voltage, alternator output, ripple). Repair if outside spec.
Check and clean main engine/chassis grounds and battery negative terminal; measure resistance to chassis/engine (< 0.5 Ω desirable).
With key ON, measure VREF at the ECM VREF pin and at each sensor on circuit A using a multimeter. Compare voltages; if missing or unstable, suspect wiring/ECM.
Use an oscilloscope to scope the VREF at the ECM and at the sensor connector with engine running. Look for excessive noise, ripple, or intermittent drops when the fault occurs.
Perform a wiggle test of the harness/connectors while monitoring VREF and affected sensor signals to reproduce the noise/interruption.
Isolate sensors: disconnect suspected sensors on circuit A one at a time and see if the code clears or noise stops. If disconnecting a specific sensor eliminates the noise, test or replace that sensor.
Check continuity and for shorts to battery voltage and ground between ECM VREF pin and each sensor; repair damaged wiring or connectors.
If wiring and sensors test good but noise persists at the ECM supply pin, consider ECM internal regulator fault. Verify with manufacturer procedures; replace ECM only after confirming external wiring and components are good.
After repairs, clear codes and road-test to confirm the issue is resolved and code does not return.

Likely causes

Open, short, or high-resistance in the VREF/sensor supply wiring or connector
Corroded or loose ground/battery connection causing reference instability
A failing sensor on circuit A intermittently loading the supply
Alternator/charging system ripple introducing noise onto the reference rail
Internal ECM regulator or driver fault (less common)

Fault status

⚠️ Status

Noisy or unstable sensor supply (VREF) detected on ECM sensor supply circuit A. Voltage exceeds noise/ripple thresholds or shows intermittent drops, causing corrupted sensor signals.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

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P1572 — Engine control module (ECM), sensor supply circuit A - noisy signal