What it means
Same as P24A7 with the control line shorted to supply. EGR mixes inert exhaust into intake to lower combustion peak temperature — too little raises NOx, too much causes misfires and rough running.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The EGR cooler coolant pump circulates coolant through the cooler to carry heat away from recirculated exhaust. The control module monitors the pump control line and sets P24AA when that line reads high, which can happen if it is shorted to supply voltage. The pump may then fail to switch as intended, risking poor EGR cooler cooling.
Common causes
Most likely first.
- Control line shorted to supply
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
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
- Record freeze-frame data and review pump command and feedback to see whether the high reading occurs with the pump on or off.
- Inspect the pump harness for pinched or melted insulation where the control wire could contact a supply wire or battery feed.
- Check the pump connector for corrosion, moisture, loose fit, or a pushed-back terminal.
- Using the manufacturer's circuit test procedure, check whether the control line is shorted to supply voltage and wiggle the harness while monitoring the circuit.
- If the wiring is not shorted to supply, test the pump and control-module output according to the manufacturer's procedure.
Common fixes
- Repair a pinched section where the pump control wire contacts a supply source.
- Clean and secure the pump connector or replace a damaged terminal.
- Repair melted or rubbed-through control-wire insulation.
- Replace the pump if an internal fault is driving the control line high.
- Repair the control module if its output is confirmed stuck high.
Can I keep driving?
Keep driving to essential trips at light load until the control-line fault is repaired, as the pump may not switch correctly and the EGR cooler can overheat. Stop if knocking worsens or the engine overheats.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.