Golf IV Cold Start Error: Codes 17831 & 18

Hi,

I have a Golf IV 1J, manufactured in 1999, with 42,000 kilometers on the odometer.
"Occasionally, when starting the engine cold, I experience a problem where, after the initial throttle input, the engine RPM fluctuates between 850 and 1200 before settling down. After about a minute, it returns to its normal idle speed and maintains it consistently. However, it's impossible to drive the car within that first minute."

At first glance, all the cables and hoses appear to be in good condition. Therefore, I checked the error memory, and the following result was obtained: -> VAG-COM version: Release 303.1

Control Module Part Number: 06A 906 033
Component and/or Version: SIMOS33 1.6l 2V 00HS3087
Software Coding: 00031
Workshop Code: WSC 00046
2 Faults Found:
17831 - Secondary Air Injection System: Bank 1: Insufficient Flow.
P1423 - 35-00 - -
18056 - Powertrain Data Bus: Failure.
P1648 - 35-10 - - - Intermittent



I've already done some searching, but I haven't found anything specific about the errors.

Thank you in advance for the information.

g ^^

I often find the throttle body completely covered in dirt, as the crankcase ventilation system (KGE) connects directly to it... do you think it will help?

Unfortunately, not... it wasn't really dirty .