P0488: EGR Throttle Control Circuit A Range/Performance

Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. The EGR throttle is a regulating flap ahead of the intake manifold on diesels: by closing partly it lowers manifold pressure below exhaust back pressure so that enough exhaust is recirculated, and it also helps filter regeneration and shuts off air at engine stop. It is usually a DC motor with position sensor. GM and Ford report this flap under P02E0 ff; no manufacturer document available to us uses this code. P0488 is its function check: the actual position reported by the sensor deviates from the target for too long, or the position signal is implausible – typically a coked, stiff flap or a broken gear. The flap then goes to its rest position or the engine enters limp mode, and the EGR rate cannot be controlled.

Symptoms

• Check engine light on
• Loss of power or limp mode possible
• Shaking when the engine is switched off
• Filter regeneration does not complete

Most likely causes

• Flap coked by soot and oil mist (EGR plus crankcase ventilation)
• Actuator gear or motor worn or broken
• Position sensor in the flap faulty or implausible
• Corrosion on flap or housing

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the connector and any vacuum hoses
2. Compare the reading with other engine data while varying the engine speed.
3. Use live data to compare the commanded opening with the actual opening
4. Clean the valve and passages if they are clogged with carbon
5. Test the actuator with the scanner
6. Replace the valve if it still does not follow the command after cleaning

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P0488 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 4: Emissions
• 88: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0488?

You can normally drive in moderation, but get it repaired soon: if the valve is stuck open, the engine may idle very poorly.

What causes code P0488?

The most common causes are: flap coked by soot and oil mist (EGR plus crankcase ventilation); actuator gear or motor worn or broken; position sensor in the flap faulty or implausible.

Related codes

• P0487EGR Throttle Control Circuit A/Open
• P02E0Diesel Intake Air Flow A Control Circuit/Open
• P02E1Diesel Intake Air Flow A Control Performance
• P0401EGR A Flow Insufficient Detected
• P0402EGR A Flow Excessive Detected

Sources

• law.cornell.edu: 13 CCR 1968.2
• ms-motorservice.com: throttle valves and regulating throttles
• patents.google.com: en

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.