P227C

Code

Generic P — Powertrain

Barometric Pressure Sensor C Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 29 EN: 50 RU: 29

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Page language: EN

Causes

Short to ground on the BARO sensor C signal wire
Open or high-resistance wiring/connector between sensor and ECM
Failed BARO sensor (internal short or failed electronics)
Poor or missing sensor reference voltage (usually 5V) or ground
Corroded or damaged connector pins
Intermittent connection due to abrasion or broken wire

Symptoms

Check Engine / MIL illuminated
Poor idle quality, stumbling or surging
Hard or extended cranking, possible hard start
Reduced engine performance or drivability issues
Poor fuel economy
Erratic barometric/MAP readings on a scan tool

What to check

Retrieve freeze-frame and live data with a scan tool; note BARO sensor C voltage and reported pressure
Check for other stored codes that could indicate shared circuits (e.g., MAP, MAF, ECM power/ground)
Visually inspect BARO sensor, wiring harness, and connector for damage, corrosion or water intrusion
Backprobe sensor connector with key ON, engine OFF to measure signal voltage, reference (5V) and ground
Wiggle wiring while watching live data for intermittent changes
Perform continuity and resistance checks from the harness connector to the ECM pin (power/ground/signal)

Signal parameters

Typical BARO signal voltage: approximately 0.5–4.5 V (varies by manufacturer)
Expected reference voltage: ~5.0 V (key ON), verify exact value per vehicle
Expected ground: near 0 V with low resistance to chassis ground
Barometric pressure: roughly 80–105 kPa (varies with altitude and weather)
Low-circuit condition: signal voltage below sensor's lower threshold (often

Diagnostic algorithm

Connect a scan tool and confirm P227C is current or pending. Record freeze-frame data and live BARO C voltage/pressure.
Visually inspect sensor and harness for damage, water, corrosion or loose connector. Repair any obvious issues.
With key ON, engine OFF, backprobe the sensor connector: verify 5V reference, signal voltage, and ground. If reference or ground is absent, trace to fuse/ECM.
If the signal is low but reference and ground are good, check continuity of the signal wire to the ECM pin. Look for short to ground (measure resistance to chassis ground).
Wiggle the harness and connectors while watching live data to identify an intermittent wiring fault.
If wiring checks good, substitute a known-good BARO sensor (or bench-test/measure sensor per manufacturer) and re-test.
If replacement sensor does not clear the low reading, perform ECM power/ground diagnostic (check ECM pin voltages and grounds) and consider ECM fault if other causes are ruled out.
After repair, clear codes and perform a drive cycle to verify repair and that code does not return.

Likely causes

Damaged signal wire shorted to chassis ground
Corroded connector at the BARO sensor
Failed BARO sensor element
Lost 5V reference or sensor ground at the harness
Aftermarket sensor or recent service disturbed wiring

Fault status

⚠️ Status

Barometric Pressure Sensor C Circuit Low — signal voltage below expected range. Check sensor, connector, wiring for short to ground or loss of reference/ground; ECM fault is possible if wiring and sensor test good.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours