Diesel Trouble Codes

P0237 — Turbocharger/Supercharger Boost Sensor A Circuit Low (LB7 Duramax)

Diagnostic reference for P0237 on LB7 Duramax (2001–2004).

Updated September 2, 2026

What it means

The engine control module has detected an abnormally low voltage signal from the boost pressure sensor circuit.1

Most likely causes

  1. Boost pressure sensor (MAP) electrical fault – low voltage / short to ground — Sensor supply, signal or ground wiring fault causing the ECM to see a low voltage on the boost sensor circuit.1
  2. Boost pressure sensor connector or wiring chafed / corroded — Damaged harness or connector at the MAP/boost sensor leading to low signal voltage.1
  3. ECM input fault for boost sensor circuit — Internal ECM reference/ground issue causing a persistent low reading on the boost sensor input.1

How to diagnose

  1. Verify code and freeze-frame; confirm P0237 is present and not accompanied by under/overboost performance codes.
  2. Inspect boost pressure sensor (MAP) connector and wiring for corrosion, oil contamination, chafing, and secure seating.
  3. Check sensor reference voltage and ground at the sensor connector with key on, engine off; compare to spec.
  4. Measure sensor signal voltage at idle and with engine running; a stuck low voltage supports a circuit fault.
  5. Inspect intake tract for damage that could affect sensor readings; LB7 uses fixed-geometry IHI turbo, no VGT actuator.
  6. If circuit tests normal, evaluate ECM inputs and consider ECM connector inspection.
  7. Clear codes and road test to confirm code return.

Parts and tools you may need

Rough cost and difficulty

Cost varies by region and labor rates; electrical diagnosis typically lower than component replacement. Obtain local quotes.

When to see a pro

If wiring tests normal but code persists, have a qualified diesel technician evaluate ECM inputs. Do not attempt high-pressure fuel system service. Seek professional help for any safety-critical repairs.

Sources

  1. Curated DTC seed — LB7 Duramax (curated) ↩︎ ↩︎ ↩︎ ↩︎