Code
P2455
ISUZU
P — Powertrain
DPD Differential Pressure Sensor Circuit High
Views:
UK: 23
EN: 74
RU: 47
AI status
Completed
Completed
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Causes
- Faulty differential pressure (DPD/DPF) pressure sensor
- Short to battery voltage in the sensor signal circuit
- Poor or corroded connector or pin making a high-voltage contact
- Open or damaged harness causing intermittent/high readings
- Poor sensor ground or reference voltage problem
- Severely clogged/restricted DPF producing an actual high differential pressure
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- DPF/regen warning messages or frequent regen cycles
- Reduced engine performance or limp mode on some vehicles
- Poor fuel economy and increased exhaust smoke
- Failure to complete DPF regeneration or regeneration errors
What to check
- Read and record freeze-frame and live data for differential pressure sensor voltage and engine operating conditions
- Visual inspection of sensor, connector and wiring for damage, corrosion, pin push-out or contamination
- Backprobe sensor connector to measure signal voltage, reference (supply) voltage and ground with key on/engine off and during operation
- Check continuity and resistance between sensor ground and vehicle chassis/ECM ground
- Measure differential pressure across DPF with diagnostic tool or hand vacuum/pressure gauge to confirm actual pressure
- Clear code and perform drive cycle to verify if fault returns after repairs
Signal parameters
- Typical sensor type: 3-wire analog (signal, 5 V reference, ground)
- Reference/supply voltage: ≈5 V (consult OEM spec)
- Signal output: approximately 0.5 V at near-zero differential to ~4.5 V at high differential pressure (consult OEM for exact curve and thresholds)
- A circuit-high DTC is triggered when signal exceeds the ECM-specified upper threshold (often near supply voltage)
Diagnostic algorithm
- Retrieve freeze frame and live data; note signal voltage, engine speed, load and whether DPF regeneration was active when code set.
- Perform a careful visual inspection of sensor, harness and connector for damage, crushed wires, corrosion or water intrusion.
- With ignition ON (engine off), backprobe the connector: verify reference voltage (~5 V) present, verify good ground continuity to chassis/ECM, and record the sensor signal voltage. A signal near supply voltage indicates circuit high.
- Wiggle test harness while monitoring signal to look for intermittent shorts; inspect for chafing or pin contact with 12V circuits.
- If wiring appears suspect, disconnect sensor and measure signal at harness connector: if signal remains high at harness, suspect wiring/ECM; if signal goes to open-circuit level or changes, suspect sensor.
- Use a hand-held vacuum/pressure pump to apply known differential pressures to the sensor and confirm the sensor signal changes smoothly within expected voltage range per OEM spec.
- Measure actual differential pressure across the DPF (front and back) with a diagnostic tool or pressure gauge to determine if the DPF is physically restricted.
- If wiring and grounds test normal but sensor output is incorrect, replace the differential pressure sensor. If actual DPF pressure is excessive, investigate and service or replace the DPF and associated exhaust restrictions.
- After repair, clear codes, run required DPF regeneration if needed, and verify the code does not return during appropriate drive cycle.
Likely causes
- Failed differential pressure sensor (internal short or output stuck high)
- Signal wire shorted to 12V or to the sensor supply (reference)
- Corroded/loose connector at the sensor causing incorrect voltage reading
- Actual high pressure differential due to blocked DPF or soot accumulation
- Bad ground at sensor or ECM causing elevated signal voltage
Fault status
Status
DPD/DPF Differential Pressure Sensor Circuit High — Sensor signal higher than ECM threshold (possible short to voltage, sensor fault, or excessive pressure differential). MIL on.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
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