P24A0: Closed Loop Particulate Filter Regeneration Control At Limit Temperature Too Low

What it means

With regeneration running closed-loop the controller is at maximum heat-input demand yet cannot raise EGT to setpoint - typical for a load-poor drive cycle.

At a glance

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

How it works

The DPF regeneration system heats the exhaust so soot can burn off, while exhaust temperature feedback lets the controller regulate that heating. P24A0 sets when the controller reaches its maximum heat demand but the measured temperature remains below the regeneration target.

Common causes

Most likely first.

1. Low engine load or repeated short trips
2. Exhaust-temperature sensor reading low or inaccurately
3. Exhaust leak reducing temperature
4. Faulty regeneration heat source or control

Symptoms

• Check engine light or DPF warning light on
• Power loss / limp mode
• Increased fuel consumption
• Failed forced regeneration attempts

How to diagnose it

1. Check freeze-frame data for trip length, speed, engine load, and regeneration status to see whether low-load driving kept exhaust temperature down.
2. Compare live exhaust temperature readings before and during regeneration, checking for implausibly low or inconsistent sensor values.
3. Inspect exhaust temperature sensor wiring and connectors for damage, corrosion, or a poor connection.
4. Look for exhaust leaks around the DPF and temperature sensors that could reduce or distort measured heat.
5. Check for related engine, heater, or regeneration-control faults that could limit the system's heat input.
6. Use the manufacturer's procedure to assess DPF soot load and determine whether a service regeneration is safe and appropriate.

Common fixes

• Repair a damaged temperature sensor connector or wiring.
• Repair exhaust leaks affecting the DPF temperature readings or heat retention.
• Replace a temperature sensor that fails testing against the manufacturer's specification.
• Repair the confirmed regeneration heat-source or control fault.
• Perform a service regeneration after correcting the cause and confirming it is safe.

Can I keep driving?

A DPF warning may progress to reduced power as soot continues to accumulate, so avoid repeated short, low-speed trips and arrange diagnosis. Do not attempt to force a regeneration if the vehicle warns against it.