P0237 — Turbocharger/Supercharger Boost Sensor A Circuit Low — 7.3 Power Stroke

Diagnostic reference for 7.3L Power Stroke (1999–2003) P0237.

Updated October 15, 2026

What it means

Generic definition: PCM sees the boost (MAP) sensor signal voltage below its valid range. On the 7.3L the MAP sensor reads boost through a small hose from the intake; a cracked, plugged or disconnected hose, an unplugged or corroded connector, or a failed sensor can set it. Expect low power because the PCM limits fuel on a bad boost signal.¹

Most likely causes

1. MAP sensor signal voltage low due to wiring/connector fault — Inspect the MAP sensor connector for corrosion, loose terminals, or unplugged condition; check the signal and reference wires for chafing, opens, or shorts to ground. Compare MAP reading key-on engine-off to barometric pressure as a sanity check.¹²
2. Boost reference hose to MAP sensor cracked, plugged, or disconnected — The 7.3L MAP sensor uses a small hose from the intake. A cracked, oil/soot-plugged, or disconnected hose causes an implausible low signal and can set P0237/P0236. Inspect the hose for cracks, collapse, oil contamination, and secure connections at both ends.¹²
3. MAP sensor internal failure — A failed MAP sensor can pull the signal low. If wiring and hose are intact, substitute/verify sensor output against a known-good unit or scan-tool data.¹³

How to diagnose

1. Verify code and freeze-frame; confirm P0237 is present and note engine conditions.
2. Key-on engine-off: compare MAP PID to barometric pressure; a grossly low reading suggests circuit/hose issue.
3. Inspect MAP sensor connector and wiring for corrosion, loose pins, or damage; repair as needed.
4. Inspect the small boost reference hose from intake to MAP sensor for cracks, plugging with oil/soot, or disconnection; replace/clean and re-secure.
5. With wiring and hose verified, check MAP sensor output voltage/signal behavior under idle and light load; compare to expected range and substitute sensor if suspect.
6. Clear codes, test drive, and confirm P0237 does not return and boost control is restored.

Common mistake to avoid

Replacing the turbo before smoke-testing the intake. Boost leaks at intercooler boots, end tanks and clamps are a common cause of low power and underboost codes, and they mimic a failing turbo. Source: BD Diesel — 6.7L Power Stroke problems and real fixes.

Parts and tools you may need

• Digital multimeter
• Scan tool with live data (MAP/BARO PIDs)
• Basic hand tools
• Replacement MAP sensor (if testing indicates failure)
• Replacement vacuum/boost reference hose and clamps

Tools you’ll need

• OBD-II scan tool — Reads P0237 and MAP PID to compare key-on barometric pressure and live boost readings for grossly low values.
• Digital multimeter — Checks MAP sensor supply, ground, and signal voltage at the connector to confirm low signal or wiring faults.
• Hand vacuum pump with gauge — Applies controlled vacuum to the MAP sensor and reference hose to verify sensor response and detect leaks or blockages.
• Inspection mirror and flashlight — Lets you see the small boost reference hose and MAP connector on the 7.3L for cracks, oil plugging, or disconnections.

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 persist, signal remains out of range after sensor/hose replacement, or you need to access high-pressure oil systems, have a qualified diesel technician diagnose and repair. Do not service high-pressure oil injection components without proper training and safety equipment.

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