Tech Tip: Audi’s Check Engine Light Is On, Trouble codes P0421and P0431

Tech Tip: Audi’s Check Engine Light Is On, Trouble codes P0421and P0431

The Check Engine Light (CEL) is on. Trouble codes P0421 (16805) and P0431 (16815) are set.

Vehicle Applications:  
2002 Audi A4 Quattro 3.0L, Vin T, Eng Cfg V6, Eng Des AVK
2002 Audi A6 Quattro Avant 3.0L, Vin T, Eng Des AVK, USA/Canada
2002 Audi A4 Quattro Avant 3.0L, Vin T, Eng Cfg V6, Eng Des AVK
2003 Audi A4 Quattro 3.0L, Vin T, Eng Cfg V6, Eng Des AVK

Customer Concern: The Check Engine Light (CEL) is on. Trouble codes P0421 (16805) and P0431 (16815) are set.

Potential Causes: Defective catalyst or leaking exhaust

Tech Tips: Refer to Volkswagen Technical Service Bulletin (TSB) Group 26 Number 05-03 and Group 26 Number 05-04 for more information concerning this trouble code. If the catalyst appears to operate well, but the trouble code returns, the Engine Control Module (ECM) may need re-flashing.

Tests/Procedures:  
Attempt to force catalyst readiness codes, with a full-function, factory-compatible scan tool, as follows:
1. Clear all trouble codes.

2. Enter Engine Address Word 01, Function 04 “Basic Settings” and Display group 198.

3. Simultaneously press the brake and accelerator pedals and the engine speed will increase to 2,200 rpm. Observe field 2 and 4. Field 2 must show Catalyst B1 OK and field 4 must show Catalyst B2 OK, if the test passes.

4. Once the test indicates catalysts are OK, then depress the accelerator pedal completely (swiftly) and then release it (brief acceleration to at least 4,000 rpm).

5. Using an infrared thermometer, measure catalyst inlet and outlet temperatures. A good operating
catalyst will be at least 150° F hotter on the outlet.

Courtesy of Identifix.

You May Also Like

Understanding Customer Clunking And Clicking Complaints

Can Your Techs Diagnose and Repair Modern Axle Complaints?

In this episode of Shop Owner Solutions, Doug Kaufman, editor of Shop Owner Magazine, interviews Miguel Cornejo, product manager for TrakMotive. They discuss the common causes of axle failure, such as road conditions, vehicle modifications, and improper installation. They also emphasize the importance of regular maintenance and inspection to prevent axle failure.

Comprehensive Guide to Serpentine Belt and Drive System Maintenance

Properly maintaining the entire drive system prevents premature belt wear and system failure, ensuring customer satisfaction and vehicle reliability.

How Modern Car Sensors Optimize Performance and Emissions

Learn how Standard ensures accuracy, speed, and durability in their sensors to maximize engine performance and efficiency.

Chassis Parts and Alignment Angles

Knowing why the adjustment is required is critical to performing the total alignment.

Top 10 Wheel Bearing Torque Tips

A torque wrench is an essential tool when it comes to installing wheel bearings.

Other Posts

Blink CEO to Present at Energy, Power & Renewables Conference

The event is scheduled for June 17 at 1:10 p.m. ET.

Tool Time Podcast: Lumileds

Nadine and Eric sit down with Lumileds’ Aubry Baugh to discuss all the professional lighting solutions the company has to offer.

Charging More May Bring Customers Back

Here’s why charging more for brake jobs keeps customers coming back.

Virginia Will Not Adopt California’s ICE Ban

SEMA applauds Virginia Governor Glenn Youngkin’s action to reverse the state’s EV mandates.