If LED does not flash and secondary air injection pump relay does not click:

Fig 1: Secondary Air Pump Relay At Relay Plate In Control Module Protective Housing

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Pull secondary air pump relay - arrow - off relay plate in control module protective housing.

NOTE:

If tools are necessary to pull relays or control modules out of the relay plate, first disconnect battery Ground (GND) strap.
Before disconnecting battery Ground (GND) strap obtain code for radios with anti-theft coding.

Connect the voltage tester VAG1527B to contacts 3 and 4 of relay plate using adapter cables from VAG1594.
Initiate Output Diagnostic Test Mode again and secondary air injection (AIR) pump relay J299.

LED must flash.

LED flashes:

Replace secondary air injection (AIR) pump relay J299.
Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory → DTC memory (functions 02 and 05), checking and erasing
Read readiness code → Readiness code, reading . If DTC memory has been erased, readiness code must be generated again:

LED does not flash:

Connect voltage tester VAG1527B to contact 3 of relay plate and body Ground (GND) using adapter cables from VAG1594.

LED must light up.

LED does not light-up:

Check wiring for open circuit between relay plate contact 3 and battery (+) using wiring diagram.

LED lights up:

Fig 2: Identifying Test Box V.A.G 1598/31 Connected To Control Module Wiring Harness

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Connect test box VAG1598/31 to control module wiring harness. Engine control module remains disconnected.
Check wire between test box socket 66 and contact 4 on relay plate for open circuit using wiring diagram.

Wire resistance: Max. 1.5 Ω

If no wiring malfunction is detected: