What Does P047C Mean?
The exhaust pressure sensor 'B' circuit voltage is below the minimum threshold expected by the ECM. This low signal typically indicates an open ground circuit, a shorted signal wire, or a failed sensor. The driver may experience a check engine light with possible reduced power mode as the ECM cannot verify exhaust backpressure conditions.
Common Causes
30%
Exhaust pressure sensor 'B' internal failure producing a low or zero voltage output
28%
Signal wire shorted to ground in the wiring harness
22%
Open circuit in the 5V reference supply to the sensor
15%
Corroded connector causing high resistance on the signal wire
5%
ECM sensor input circuit fault
Diagnostic Steps
1
Check the exhaust pressure sensor 'B' signal voltage at the ECM connector with KOEO — a reading below 0.2V confirms a low circuit. Normal KOEO reading should be approximately 0.5V-1.0V (atmospheric).
2
Disconnect the sensor and measure the 5V reference at the sensor connector. If missing or low, check for a short on the shared 5V reference bus that could pull down voltage to all sensors on that circuit.
3
With the sensor disconnected, check if the signal wire reads near 5V (pulled up by the ECM). If it reads near 0V, the signal wire is shorted to ground somewhere in the harness.
4
Inspect the harness for damage, especially where it routes near metal edges, exhaust components, or frame members. Look for bare wire contacting chassis ground.
5
If wiring is intact, measure the sensor output by applying known pressures with a hand pump. Output should increase linearly from ~0.5V at 0 kPa to ~4.5V at full scale. Replace if output stays low.
Estimated Repair Cost
$80 - $450
Parts + labor, varies by vehicle and location
The exhaust pressure sensor 'B' circuit voltage is below the minimum threshold expected by the ECM. This low signal typically indicates an open ground circuit, a shorted signal wire, or a failed sensor. The driver may experience a check engine light with possible reduced power mode as the ECM cannot...
The most common cause of P047C (Exhaust Pressure Sensor "B" Circuit Low) is: Exhaust pressure sensor 'B' internal failure producing a low or zero voltage output
Typical repair costs for P047C range from $80 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive short distances. The ECM may enter a limited power mode to protect the engine. DPF regeneration will likely be suspended, so avoid extended driving to prevent DPF plugging.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P047C to identify the root cause.
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Quick Info
Category
Powertrain
System
Exhaust / Emissions System
Difficulty
Type
Generic (SAE)
Recommended Tools
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