P04FA

What it means

P04FA means the engine control unit has seen the temperature measured in the EGR 'A' circuit rise above the limit it expects for the current operating conditions. The reading usually comes from an EGR temperature sensor or a cooler outlet sensor. Exactly where it is measured and the limit used depend on the model and engine, so check the manufacturer data for that vehicle.

Symptoms

• Engine management warning light on
• Reduced power or the car going into a limp mode on some models
• Rough running or hesitation under load
• Higher than normal engine or coolant temperature
• Other EGR, boost or coolant temperature codes stored alongside

Possible causes

• Clogged, leaking or degraded EGR cooler, so recirculated exhaust gas is not being cooled enoughlikely
• Low coolant level, air in the cooling system, or poor coolant flow through the EGR cooler (faulty thermostat or water pump)likely
• EGR valve or cooler bypass flap stuck or sticking, sending gas through the wrong path or passing too much hot gaspossible
• Faulty EGR temperature sensor, or damaged wiring or connector giving a false high readingpossible
• Exhaust temperatures abnormally high because of an engine problem such as misfire, lean running or a restricted exhaustpossible
• Sooty or blocked EGR passages restricting flow and disturbing the temperature the sensor seespossible
• Outdated or faulty control unit calibration, where the manufacturer has issued a correction for this coderare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting engine temperature, load and speed when the code set
2. Check the coolant level and condition, and look for leaks, oil contamination or signs of exhaust gas in the coolant
3. Inspect the EGR temperature sensor wiring and connector for heat damage, chafing, corrosion and water ingress
4. Compare the live EGR temperature reading with coolant and intake temperatures on a cold engine; it should agree closely
5. Check the thermostat and the cooling fan operation, and confirm the engine reaches and holds normal temperature
6. Command the EGR valve and any bypass flap with a scan tool and watch for correct movement and a sensible change in temperature
7. Inspect the EGR valve, cooler and pipework for carbon build-up, blockage or leaks, following the manufacturer's procedure
8. Check for misfires, fuelling faults and exhaust restriction, and check whether a calibration update exists for this code on this model

How to fix

• Top up and bleed the cooling system, and repair any leak, then replace a faulty thermostat or water pump if found
• Replace the EGR cooler if it is blocked, leaking or no longer cooling effectively
• Clean or replace a sticking EGR valve or bypass flap and its actuator, as the manufacturer specifies
• Replace the EGR temperature sensor, or repair the wiring and connector fault
• Repair the underlying engine fault causing high exhaust temperatures, such as misfires or a restricted exhaust
• Apply a manufacturer calibration update only if a technical bulletin shows it covers this fault

Can I keep driving?

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