P0474
Exhaust Pressure Sensor A Circuit Intermittent/Erratic
Exhaust / emissions
Generic OBD-II
Medium
What it means
P0474 means the exhaust pressure (back-pressure) sensor "A" is sending an intermittent or erratic signal to the ECM. This sensor helps manage EGR flow and, on diesels, DPF regeneration. The cause is usually a failing sensor, a loose connector, or wiring that breaks contact as it moves. The engine still starts and runs, though diesels may briefly enter reduced-power mode.
Medium
Can I keep driving? Yes — the car starts and drives. On diesels it may occasionally drop into reduced-power (limp) mode, so plan to get it fixed.
Common symptoms
What you'll notice
- Check-engine light on
- Occasional reduced power or limp mode (common on diesels)
- Slightly reduced fuel economy
- Possible rough or erratic running under load
Common causes
Most likely first
- Faulty exhaust pressure (back-pressure) sensor ALikely
- Intermittent break, chafe, or short in the sensor wiringCommon
- Loose or corroded electrical connector at the sensorCommon
- Blocked or cracked pressure sensing tube/portLess often
- ECM fault (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and watch the sensor's live signal while wiggling the harness to catch the intermittent fault.
- Inspect the connector and wiring for corrosion, loose pins, or chafing.
- Check the sensor's sensing tube/port for blockage, soot, or cracks.
- Test the sensor's signal against spec and replace it if erratic.
- Repair wiring or replace the sensor, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0474?+
Short-term yes — the engine still starts and runs. On diesels the code can trigger reduced-power mode intermittently, which is safe but inconvenient, so repair it soon.
Can I just clear P0474?+
You can, but an intermittent fault like this usually returns. The 'intermittent/erratic' label means you'll likely need to catch it by wiggle-testing the wiring.
Related codes
Often seen with P0474
Read & clear P0474 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX