P0192 — Fuel Rail Pressure Sensor Circuit Low Input — LB7 Duramax

The ECM sees the fuel rail pressure sensor signal voltage lower than expected on the LB7 Duramax.

Updated October 15, 2026

What it means

The ECM detects the fuel rail pressure sensor signal voltage is lower than expected.¹

Most likely causes

1. Rail pressure sensor electrical fault (sensor internal failure, connector corrosion, wiring short to ground or open). — On the LB7 Duramax the rail pressure sensor circuit low typically presents as an electrical fault in the sensor/wiring rather than a mechanical rail pressure issue.²
2. Chafed or damaged wiring harness to the rail pressure sensor¹
3. ECM input circuit fault. — The engine control module detects the fuel rail pressure sensor signal voltage is lower than expected.¹

How to diagnose

1. Verify freeze frame and confirm P0192 is present with no accompanying rail pressure performance codes.
2. Inspect rail pressure sensor connector and wiring for corrosion, oil intrusion, chafing, and proper pin tension.
3. Check sensor reference voltage and signal return at the sensor connector with key on engine off; compare to spec.
4. Monitor rail pressure sensor PID with scan tool during key on and cranking; look for stuck low voltage.
5. Inspect ECM harness connector and related grounds for moisture/corrosion.
6. If electrical tests pass, substitute a known-good rail pressure sensor and retest.
7. Clear codes and road test to confirm repair.

Parts and tools you may need

• Digital multimeter
• Scan tool with live data
• Wiring diagram
• Contact cleaner
• Replacement rail pressure sensor

Tools you’ll need

• digital multimeter — Measures reference voltage, signal return, and continuity to confirm low sensor voltage and wiring faults for P0192.
• OBD-II scan tool — Reads P0192 freeze frame and monitors rail pressure sensor PID voltage to verify stuck low signal during key on and cranking.
• fuel pressure gauge — Provides actual rail pressure to compare against sensor PID and rule out mechanical pressure issues while diagnosing electrical low voltage.
• inspection mirror and flashlight — Allows visual inspection of the rail pressure sensor connector and harness for corrosion, oil intrusion, and chafing in tight engine locations.

Rough cost and difficulty

Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

If wiring faults are found in the main harness or ECM connector shows damage, have a professional diagnose and repair to avoid intermittent faults.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources