2021 Audi Rear Defogger Not Working TSB 2058452/4

Symptoms

Owners of certain 2021 Audi models may notice that their Audi rear defogger not working correctly. The primary symptom is that "The rear window defog button will light up for a second when pressed, then immediately turn off." Importantly, diagnostic scans will show "No DTCs are stored" related to this issue.

Technical Background

According to Audi, the root cause of the "Rear window defogger is not operational" condition is that the comfort system central control module, identified as J393 (address word 0046), becomes locked in a loop and requires a reset. This software malfunction prevents the defogger from functioning as intended.

Diagnosis and Trigger Conditions

To diagnose this issue, technicians will first attempt to reproduce the customer's concern. It's important to note that for the rear window defog feature to operate, the ambient temperature must be below 95°F (35°C), and the engine must be running. If the concern cannot be duplicated under these conditions, this TSB may not apply.

Repair Procedure Summary

The repair primarily involves updating the software for the comfort system central control module (J393). Here's a summary of the steps:

1. Verify Concern: Confirm the Audi rear defogger not working symptom as described by the customer.
2. Check Control Module Part Number: Using ODIS diagnostic software, check the part number of the comfort system central control module, J393 (address word 0046). If the part number begins with 8W0, the module must be replaced with the superseded 8W1 part number. Technicians should consult the parts catalog for the latest part number.
3. Software Version Management (SVM): Follow the instructions in TSB 2011732, titled "00 Software Version Management (SVM), operating instructions."
4. Update Software: If the J393 part number starts with 8W1 and its software version (SW) is below 585, the comfort system central control module, J393 (address word 0046), needs a software update using the SVM action code provided in the table below.

Required Tools or Parts

The primary part that may be required is the comfort system central control module. If replacement is necessary, the new part number will be 8W1907064* (where * denotes various suffixes). Technicians should always check with their Parts Department and/or ETKA for the latest information and parts bulletins.

SVM Software Update Table

The following table details the applicable part numbers, software versions, and SVM codes for the software update:

Model	Old Software Part Number	Old Software Version	Old Hardware Part Number	New Software Part Number	New Software Version (or higher)	SVM Code
B9 sportback, B9 Coupe, B9 Avant, B9 Limousine	8W1907064AA	0529	8W1907064A	8W1907064CA
		0530
		0542
	8W1907064BA	565
	8W1907064CA	584
B9 sportback, B9 Cabriolet, B9 Coupe, B9 Avant, B9 Limousine, Q7	8W1907064AB	0529	8W1907064B	8W1907064CB	585	46A031
		0530
		0542
	8W1907064BB	565
	8W1907064CB	584
	8W1907064AC	0529	8W1907064C	8W1907064CC
		0530
		0542
B9 sporback, B9 Cabrio, B9 Coupe, B9 Avant, B9 Limousine, Q8, Q7	8W1907064BM	565	8W1907064M	8W1907064CM
	8W1907064CM	584
	8W1907064AN	529	8W1907064N	8W1907064CN
		0530
	8W1907064AP	0542
	8W1907064BP	565	8W1907064P	8W1907064CP
	8W1907064CP	584
Audi e-tron quattro, Audi e-tron sportback quattro	8W1907064AQ	0529	8W1907064Q	8W1907064CQ
		0530
	8W1907064BQ	565
	8W1907064CQ	584
	8W1907064AR	0529	8W1907064R	8W1907064CR
		0530
		0542
	8W1907064BR	565
	8W1907064CR	584

What Owners Should Know

This Technical Service Bulletin (TSB 57 23 02 2058452/4) supersedes an earlier bulletin, Group 57 number 21-86, dated November 10, 2021. The repair for the Audi rear defogger not working issue is covered under warranty for vehicles up to 48 months or 50,000 miles, whichever comes first. For Audi Certified Pre-Owned (CPO) vehicles, specific conditions (G10) apply, and owners should verify coverage. "If the vehicle is outside any warranty, this Technical Service Bulletin is informational only," meaning the cost of diagnosis and repair would likely fall to the owner.

Owner Action

If you are experiencing your Audi rear defogger not working as described, you should schedule an appointment with an authorized Audi service center. Be prepared to describe the symptoms, specifically that the "rear window defog button will light up for a second when pressed, then immediately turn off." The service center will perform the necessary diagnostic checks and software updates or module replacements as outlined in this TSB.

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Source: NHTSA ID: 10233544