Diesel Trouble Codes

P0232 — Turbocharger Boost Sensor A Circuit High (5.9 Cummins 24-Valve (VP44))

Diagnostic reference for 5.9L Cummins 24-Valve VP44 (1998.5–2002) when ECM reports P0232. Focus on electrical diagnosis of the boost pressure sensor circuit…

Updated September 2, 2026

What it means

The ECM has detected an abnormally high voltage signal from the turbocharger boost pressure sensor circuit. On this platform the turbo is a fixed-geometry Holset HX35/HY35 with no variable geometry or electronic VGT actuator [authoritative platform facts]. A boost code therefore points to the boost/MAP sensor circuit, wiring, or a boost leak rather than VGT vanes [authoritative platform facts].1

Most likely causes

  1. Boost pressure sensor (MAP) internal failure causing high voltage output — Sensor biased high or shorted internally, producing voltage above expected range.1
  2. Wiring short to voltage or chafed harness raising signal voltage — Boost sensor signal wire shorted to a higher voltage source or grounded/shorted due to chafing, connector corrosion, or pin damage.1
  3. Connector or terminal corrosion / poor contact at boost sensor — Oxidized or loose connector increases resistance or creates intermittent high-voltage readings.1
  4. Boost leak causing abnormal pressure readings interpreted as circuit high — Large pre-throttle boost leak can cause erratic sensor behavior; platform has fixed-geometry turbo, so boost control issues are mechanical leaks or sensor faults, not VGT [authoritative platform facts].1
  5. ECM input circuit fault — Internal ECM reference or pull-up fault causing high voltage reading on the sensor input.1

How to diagnose

  1. Verify code and freeze frame; confirm P0232 is present and note engine conditions at set.
  2. Visually inspect boost pressure sensor, wiring, and connectors for damage, oil contamination, corrosion, or chafing.
  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; look for voltage stuck high or out of range.
  5. Inspect intake tract for boost leaks (intercooler pipes, boots, clamps) consistent with fixed-geometry turbo system.
  6. Perform wiggle test on harness and connector while monitoring live data to reveal intermittent high readings.
  7. If electrical values are normal, compare boost sensor reading to a known-good scan tool reading or substitute sensor to isolate sensor vs circuit fault.
  8. Check ECM connector and pins for corrosion or damage; verify ECM power/ground integrity before condemning ECM.

Parts and tools you may need

Rough cost and difficulty

Parts cost varies by brand and region; labor depends on shop rates and diagnostic time. Electrical diagnosis typically requires minimal parts unless sensor or wiring replacement is needed.

When to see a pro

If wiring faults are found in high-pressure fuel areas, or if ECM replacement is suspected, have a qualified diesel technician perform diagnosis and repair. Do not attempt repairs on high-pressure fuel lines or safety-critical systems without proper training and tools.

Sources

  1. Curated DTC seed — 5.9 Cummins 24-Valve (VP44) (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎