P047C: Exhaust Pressure Sensor B Circuit Low

What it means

Exhaust pressure sensor B below lower plausibility — short to ground. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

Exhaust pressure sensor B measures pressure in the exhaust system for functions such as DPF monitoring or turbo control. The control module sets P047C when sensor B’s circuit signal falls below the expected lower range, commonly because the signal is shorted to ground or has a poor connection.

Common causes

Most likely first.

1. Short to ground
2. Connector pins corroded - high contact resistance
3. Harness chafing through insulation

Symptoms

• Check-engine light on
• Possible reduced engine power
• Possible increased exhaust smoke
• Possible reduced fuel economy

How to diagnose it

1. Record freeze-frame data and check live sensor B data to confirm the low reading and the conditions when it occurs.
2. Inspect sensor B’s connector and harness for corrosion, pin damage, or insulation rubbed through to ground.
3. Check the sensor B signal wire for a short to ground using the wiring diagram and manufacturer’s procedure.
4. Test connector terminal contact and circuit continuity, paying particular attention to corroded pins or damaged grounds.
5. Test sensor B against the manufacturer’s specification after verifying its wiring and pressure passage.

Common fixes

• Clean and secure corroded or loose sensor B connector terminals.
• Repair the sensor B signal wire where it is shorted to ground or chafed.
• Repair a damaged connector or harness section causing poor contact.
• Replace sensor B if its output remains below specification with a sound circuit.

Can I keep driving?

If the engine runs normally, drive gently and avoid heavy loads or towing. A false low pressure reading can disrupt DPF or turbo control and may bring reduced power or increased smoke.