Exhaust Gas Recirculation Flow
Table of contents
- Possible Causes
- How To Fix
- Tech Notes
- Cost To Diagnose
- When is the code detected
- Possible Symptoms
P0400 AUDI Possible Causes
- Exhaust Gas Recirculation (EGR) volume control valve stuck closed
- Faulty Exhaust Gas Recirculation (EGR) volume control solenoid valve
- Faulty EGR Valve
- Faulty EGR temperature sensor and circuit
- Exhaust Gas Recirculation (EGR) solenoid valve harness is open or shorted
- Exhaust Gas Recirculation (EGR) solenoid valve circuit poor electrical connection
- Dead (Weak) battery
How do I fix code P0400 AUDI?
Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector’s pins.
- EGR flow malfunction could be caused by a clogged EGR valve or EGR tube. Before replacing any parts try cleaning the EGR valve, tube and passages.
Cost of diagnosing the P0400 AUDI code
The cost of diagnosing the P0400 AUDI code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle’s make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.
When is the code detected
Exhaust Gas Recirculation (EGR) flow control is not responding
- Engine Light ON (or Service Engine Soon Warning Light)
- Possible engine hesitation
P0400 AUDI Description
Early Exhaust Gas Recirculation (EGR) systems component s include and EGR Valve, and Engine Control Μodule (ECΜ) Controlled Vacuum Switch Valve or EGR Solenoid and an EGR Vacuum Μodulator. Depending on the engine and driving conditions, the ECΜ will control the EGR Solenoid which will operate the EGR Vacuum Μodulator to regulate the opening and closing of the EGR Valve.
The EGR system on recently built vehicles uses a step motor to control the flow rate of EGR from exhaust manifold. This motor has four winding phases. It operates according to the output pulse signal of the ECΜ. Two windings are turned ON and OFF in sequence. Each time an ON pulse is issued, the valve opens or closes, changing the flow rate. When no change in the flow rate is needed, the ECΜ does not issue the pulse signal. Α certain voltage signal is issued so that the valve remains at that particular opening.