Diesel Trouble Codes

DTC 125 — Injection Control Pressure Signal Out of Range – High — International DT466E

Navistar three-digit code for the International DT466E (1996–2003) HEUI engine. The ECM sees the ICP sensor voltage above its valid range. Diagnose the ICP…

Updated October 15, 2026

What it means

DTC 125 means the ECM is reading the Injection Control Pressure (ICP) sensor signal voltage above its valid range on the DT466E HEUI system. The code is a sensor-signal fault, not a confirmation that actual injection control pressure is high.1

Most likely causes

  1. Failed ICP sensor internally biased high — The ICP sensor can fail and output a voltage above the normal range, setting DTC 125.1
  2. ICP signal circuit shorted to voltage / wiring fault — A short to battery or 5 V reference on the ICP signal wire raises the voltage seen by the ECM.1
  3. Oil intrusion into ICP connector causing high bias — Oil in the ICP connector can contaminate the sensor terminals and skew the signal high.2
  4. ECM reference/ground issue affecting ICP reading — A poor ECM ground or reference voltage problem can make the ICP signal appear high.1

How to diagnose

  1. Verify the code is active and note freeze-frame conditions; clear codes and retest to confirm repeatability.
  2. Inspect the ICP sensor and harness for oil in the connector, damaged wiring, chafing, and corrosion; repair as needed.
  3. Disconnect the ICP sensor and check the ECM reference voltage and ground at the harness with key on; compare to spec.
  4. Measure the ICP sensor signal voltage at idle and during cranking with a scan tool or DVOM; look for voltage above the valid range.
  5. If the signal is high with the sensor disconnected, suspect a short to voltage in the signal wire or ECM fault; if the signal is normal with a known-good sensor, replace the ICP sensor.
  6. After repair, clear codes and run the engine through idle and load to confirm DTC 125 does not return and ICP pressure readings are plausible.
  7. If DTC 331 or DTC 334 also appear, evaluate the high-pressure oil system (IPR valve, high-pressure oil pump, leaks) separately, as those codes indicate actual pressure issues.

Parts and tools you may need

Tools you’ll need

Rough cost and difficulty

Likely repairPartsShop laborWho usually does it
Wiring or connector repair$10–$1001–4 hrsDIY with tools and a manual
ICP (injection control pressure) sensor$60–$2000.5–1.5 hrsDIY with tools and a manual
ECM/PCM replacement (programmed)$600–$2,0001–3 hrsShop

Typical US independent-shop figures; labor runs about $140–$200 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

If the signal wire tests shorted to voltage inside the harness or the ECM shows abnormal reference voltage, have the harness and ECM evaluated by a qualified diesel technician. If DTC 125 persists after sensor and wiring repair, or if accompanying high-pressure oil codes (e.g., DTC 331, 334) appear, professional diagnosis of the HEUI high-pressure oil system is required.

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

  1. Curated DTC seed — International DT466E (curated) ↩︎ ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — International DT466E (curated) ↩︎