Troubleshooting Touran Webasto with VCDS: Overheating and Locking Issues

This article addresses troubleshooting a persistent Webasto auxiliary heating problem in a Volkswagen Touran using VCDS diagnostic software. The issue involves the heater overheating and subsequently locking out, preventing operation. We’ll delve into the symptoms, fault codes, attempted solutions, and steps for further diagnosis using VCDS.

Symptoms of a Malfunctioning Webasto Heater

Several symptoms indicated a problem with the auxiliary heating system:

• Intermittent Failure to Start: The Webasto heater would sometimes fail to initiate, accompanied by an error message on the multi-function display (MFD).
• Slow Engine Warm-up: The engine took longer than usual to reach operating temperature, particularly during low-speed driving or idling. Normal operating temperatures were 90°C for coolant and 80-105°C for oil. With the malfunction, oil temperature hovered between 65-75°C. Adequate warm-up only occurred during high-speed driving (110+ km/h) or uphill climbs.
• Temperature Drops at Idle: Coolant and oil temperatures would decrease noticeably when the vehicle was idling or driven at low speeds in city traffic or downhill.
• Lukewarm Air from Heater (Initially): Although the Webasto unit would sometimes run a full 20-minute heating cycle, the air delivered into the cabin was only lukewarm, indicating incomplete combustion or inefficient heat transfer.

Initial VCDS Fault Codes and Attempted Repairs

The initial VCDS scan revealed the following fault codes:

01410 - Heater Over-Temp
01411 - Temperature Sensor (G18) - Short to Ground
02251 - Heater Unit Locked

Initial VCDS Scan

Based on these codes, a mechanic replaced the DSG temperature sensor and the G18 temperature sensor (OEM part number 1K0815111A). The heater was unlocked and fault codes cleared after each repair. Initially, these replacements seemed successful, restoring normal engine operating temperatures and producing hot air from the Webasto unit. However, the issue reappeared after a few days each time.

Recurring Fault Codes Pointing to Overheating

The problem returned, with the Webasto heater locking out again. This time, the VCDS scan showed only two fault codes:

01410 - Heater Over-Temp
02251 - Heater Unit Locked

The recurring 01410 error clearly indicates an overheating condition within the Webasto unit, leading to the 02251 lockout to prevent damage.

Further Diagnostic Steps with VCDS

To pinpoint the root cause of the overheating, further diagnostics using VCDS are necessary. Possible areas to investigate include:

• Fuel Supply: Check fuel pressure and flow to the heater. Insufficient fuel delivery can lead to incomplete combustion and overheating. Use VCDS to monitor fuel pump operation and pressure readings.
• Combustion Air Intake: Inspect the air intake for obstructions or restrictions. A lack of sufficient combustion air can also cause overheating.
• Exhaust System: Verify that the exhaust system is clear of any blockages. Back pressure in the exhaust can lead to overheating.
• Coolant Circulation: Ensure proper coolant flow through the Webasto unit. Air pockets or a faulty circulation pump can cause localized overheating. VCDS can be used to activate the circulation pump and monitor coolant temperature.
• Glow Plug and Flame Sensor: Test the glow plug for proper operation and the flame sensor for accurate flame detection. A malfunctioning glow plug or flame sensor can disrupt the combustion process, leading to inefficient heating and potential overheating. Utilize VCDS output tests to check these components.

Addressing a Pre-existing Fault Code

A pre-existing, potentially unrelated fault code was also present:

9477489 - Motor for Air Distribution Flap B109D - Actuator stuck

While this fault likely pertains to the vehicle’s climate control system and not directly to the Webasto heater, it’s worth investigating and resolving to eliminate any potential indirect effects.

Conclusion: Pinpointing the Root Cause

The persistent overheating and lockout of the Touran’s Webasto heater necessitate a systematic diagnostic approach using VCDS. Focusing on fuel supply, combustion air intake, exhaust system, coolant circulation, and the glow plug/flame sensor will help isolate the root cause and lead to a lasting repair. By using VCDS measuring blocks and output tests as described, a more precise diagnosis can be achieved.