Exhaust Pressure Sensor "A" Circuit Low
P0472 indicates the exhaust pressure sensor is sending a voltage signal lower than expected to the PCM. This sensor monitors exhaust backpressure in diesel or turbocharged engines to control variable nozzle turbochargers and diesel particulate filter regeneration. A low signal typically means an electrical fault in the sensor circuit or sensor failure.
What You Might Notice
- Check Engine Light illuminated
- Lack of engine power or reduced performance
- Unable to perform diesel particulate filter regeneration
- Potential limp mode operation
- Turbocharger boost control issues
Most Common Causes
- 1
Exhaust pressure sensor failure
The sensor itself may be internally shorted to ground or have failed, preventing it from generating proper voltage signals to the PCM.
- 2
Open signal wire or connector
A broken or disconnected signal wire between the exhaust pressure sensor and PCM prevents voltage from reaching the module, causing a low input signal.
- 3
Short to ground in signal circuit
A damaged wire or terminal in the signal circuit that contacts ground will pull the signal voltage down to near zero volts.
- 4
Open power supply circuit
Loss of power to the sensor due to a broken wire, bad connector, or blown fuse in the supply circuit prevents the sensor from operating.
How to Diagnose It
- 1
Check Exhaust pressure sensor failure — The sensor itself may be internally shorted to ground or have failed, preventing it from generating proper voltage signals to the PCM.
- 2
Check Open signal wire or connector — A broken or disconnected signal wire between the exhaust pressure sensor and PCM prevents voltage from reaching the module, causing a low input signal.
- 3
Check Short to ground in signal circuit — A damaged wire or terminal in the signal circuit that contacts ground will pull the signal voltage down to near zero volts.
- 4
Check Open power supply circuit — Loss of power to the sensor due to a broken wire, bad connector, or blown fuse in the supply circuit prevents the sensor from operating.
How to Fix It
- 1
Test and replace exhaust pressure sensor
Use a multimeter to verify sensor voltage under load; if voltage is below specification or shorted to ground, replace the sensor with a new one. Verify connector cleanliness and proper seating.
- 2
Inspect and repair signal wiring
Visually inspect the signal wire between the sensor and PCM for breaks, pinches, or abrasion. Use a multimeter to check for continuity and shorts to ground. Repair or replace damaged wiring as needed.
- 3
Check connector and terminals
Disconnect the sensor connector and inspect pins for corrosion, bending, or looseness. Clean contacts with electrical contact cleaner and reconnect firmly. Check for corrosion at the PCM connector as well.
- 4
Verify power supply and fuse
Check the dedicated fuse for the exhaust pressure sensor circuit and replace if blown. Verify 5V or 12V supply voltage (depending on vehicle) is present at the sensor connector with ignition on.
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