Gerard at Autotechniek Cappon saw the value of the IVS 360 support service with a little help from Ben, one of our master technicians.
Customer Complaint
The customer reported engine power loss, most noticeable during acceleration and high-load driving conditions
Fault Codes Retrieved
- P0402 – EGR Flow Excessive Detected
- Boost sensor–related faults (intermittent)
Initial Technical Assessment
Communication between Gerard and Ben highlighted several possible causes for the symptoms reported:
Boost Sensor / MAP Sensor Accuracy
- With ignition on → sensor should read approx. 1 bar (atmospheric pressure).
- With engine running → actual vs. specified boost should be within ~50 mbar.
- Known issues on this model:
- Weak/loose pins in the boost sensor connector
- Wiring degradation causing incorrect readings
Incorrect boost readings can contribute to power loss and can also falsely trigger EGR-related diagnostic faults.
EGR System Overview (Audi 2.0 TDI)
This engine variant typically uses two EGR systems:
Low-Pressure EGR System
- Located at the rear of the engine, with an EGR tube running from behind the turbo.
- Includes a round EGR cooler that returns exhaust gases to the DPF.
- These coolers are known to become heavily carbon-contaminated, causing:
- Restricted exhaust flow
- Incorrect EGR measurement
- Faults such as P2002 (DPF efficiency), though P0402 can also occur, depending on flow characteristics
High-Pressure EGR System
- Located at the front of the engine, behind the throttle valve and bolted to the cylinder head.
- Generally reliable with very few field failures.
- Occasionally, carbon accumulation may cause partial sticking, but it is usually easy to clean.
Charge Cooler (Intercooler Integrated Into Inlet Manifold)
A common failure point on this engine family:
- Charge coolers can become blocked internally due to:
- Soot/oil condensation
- Internal baffle collapse or expansion
- Consequences:
- Airflow restriction leading to boost deviation
- EGR flow measurement errors
- Reduced performance and P0402-related faults
Diagnostic Methods Recommended
- Remove throttle valve to visually inspect charge cooler internals.
- Insert a camera through the upper temperature sensor port for internal inspection.
- Measure pressure drop across the cooler:
- Normal pressure drop ≈ 0.25 bar
- Higher values indicate restriction.
Both the boost and EGR faults can be related if excessive intake restriction is present.
Technician Actions Taken
Gerard carried out the recommended checks:
Camera Inspection
Using the EGR gas cooler’s temperature sensor port, an internal camera inspection revealed:
- Severe carbon contamination
- Heavy internal buildup restricting exhaust gas flow
Root Cause Identified
The primary cause of the power loss and P0402 fault was diagnosed as a blocked low-pressure EGR gas cooler.
This restriction created:
- Incorrect EGR flow readings
- Possible boost deviations due to airflow disruption
- Resulting drivability complaints
Corrective Action
- Replace the EGR gas cooler
- Retest engine performance and boost sensor values after installation
- Clear DTCs and perform an EGR adaptation/learning procedure if required
Acknowledgment
Gerard expressed appreciation for the technical guidance provided:
“Most of all, Ben, I want to sincerely thank you for the technical advice you sent to me; it’s invaluable.
You’re a master technician – well done.”