P049C: EGR B Flow Excessive Detected

What it means

Same as P049A but with measured flow above the required rate - typically EGR valve sticking open or position sensor offset low.

At a glance

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

How it works

EGR B meters exhaust gas back into the engine to control combustion temperature and emissions. The control module compares requested operation with flow feedback; P049C specifically means measured EGR B flow is greater than required, which can happen if its valve remains open or feedback is inaccurate.

Common causes

Most likely first.

1. EGR valve B sticking open
2. Position sensor reads low

Symptoms

• Check engine light on
• Pinging or knocking under load
• Power loss and hesitation
• Possible rough idle
• Failed emissions inspection (NOx)

How to diagnose it

1. Check freeze-frame data and compare commanded EGR B operation with flow and position feedback to confirm when excess flow was detected.
2. Identify EGR B using the vehicle's service information and inspect the valve, cooler passages, connector, and wiring for damage or deposits.
3. With a scan tool, command EGR B closed and check whether position and flow feedback return to the expected closed-state readings.
4. Test whether the EGR B valve seals and moves freely according to the manufacturer's procedure.
5. If the valve closes correctly, test the EGR B position sensor and wiring for a low or biased reading against the manufacturer's specification.

Common fixes

• Clean deposits that prevent EGR B from closing fully.
• Repair damaged EGR B wiring or connector terminals.
• Replace an EGR B valve that sticks open or fails to seal.
• Replace a position sensor only if its readings fail the specified test.

Can I keep driving?

Excess EGR B flow can cause rough running, stalling, or loss of power, so avoid driving if the engine cannot idle reliably or respond safely. If it runs normally, keep trips short and gentle until diagnosed.