AUDI • 2020–2026Luxury

Audi A4 OBD-II Diagnostic Guide

Comprehensive diagnostic trouble code telemetry, sensor voltage thresholds, and step-by-step repair manuals for Audi A4 models equipped with 2.0L TFSI Turbo 4-Cyl (EA888 Gen 4 201HP–261HP).

DLC OBD-II Port: Under driver side dashboard near hood release lever (pink/purple port)

2020–2026

Engine Powertrain

2.0L TFSI Turbo 4-Cyl (EA888 Gen 4 201HP–261HP)

Factory Tolerances

Dealership Labor Rate

$170/hr

Audi Certified Shop

O2 / MAF Sensor Part

$175 - $310

Direct-Fit OEM Unit

Diagnostic Protocol

SAE J1979 / ISO 15765

16-Pin DLC Gateway

Other Audi Vehicle Models:

Audi A4 Audi Q5

Model-Specific Telemetry

Top Check Engine Trouble Codes for Audi A4

P0420A4 Specific

Est. DIY Parts: $400 - $1,800 (DIY: $150 - $400)

P0420 on Audi A4: Diagnosis & Fix

Troubleshooting procedure for P0420: P0420: Catalyst System Efficiency Below Threshold (Bank 1) specifically affecting Audi A4 (2.0L TFSI Turbo 4-Cyl (EA888 Gen 4 201HP–261HP)).

5-Step DIY GuideFix A4

P0171A4 Specific

Est. DIY Parts: $80 - $350 (DIY: $15 - $70)

P0171 on Audi A4: Diagnosis & Fix

Troubleshooting procedure for P0171: P0171: System Too Lean (Bank 1) specifically affecting Audi A4 (2.0L TFSI Turbo 4-Cyl (EA888 Gen 4 201HP–261HP)).

5-Step DIY GuideFix A4

P0300A4 Specific

Est. DIY Parts: $100 - $600 (DIY: $30 - $120)

P0300 on Audi A4: Diagnosis & Fix

Troubleshooting procedure for P0300: P0300: Random or Multiple Cylinder Misfire Detected specifically affecting Audi A4 (2.0L TFSI Turbo 4-Cyl (EA888 Gen 4 201HP–261HP)).

5-Step DIY GuideFix A4

P0299A4 Specific

Est. DIY Parts: $200 - $1,500 (DIY: $50 - $250)

P0299 on Audi A4: Diagnosis & Fix

Troubleshooting procedure for P0299: P0299: Turbocharger / Supercharger Underboost Condition specifically affecting Audi A4 (2.0L TFSI Turbo 4-Cyl (EA888 Gen 4 201HP–261HP)).

5-Step DIY GuideFix A4

P0128A4 Specific

Est. DIY Parts: $120 - $300 (DIY: $25 - $60)

P0128 on Audi A4: Diagnosis & Fix

Troubleshooting procedure for P0128: P0128: Coolant Temperature Below Thermostat Regulating Temperature specifically affecting Audi A4 (2.0L TFSI Turbo 4-Cyl (EA888 Gen 4 201HP–261HP)).

5-Step DIY GuideFix A4

Full Diagnostic Library

All OBD-II Codes for Audi A4

Showing 1–18 of 122 codes

Active:

1. Filter by Vehicle Manufacturer (25 Makes)

2. DTC System Category

3. Risk Severity Level

P0300Critical Severity

Est. DIY: $100 - $600 (DIY: $30 - $120)

P0300: Random or Multiple Cylinder Misfire Detected

Flashing Check Engine Light (CEL) • Engine shaking, vibrating, or jerking at idle

5 Step DIY GuideTroubleshoot

P0420Medium Severity

Est. DIY: $400 - $1,800 (DIY: $150 - $400)

P0420: Catalyst System Efficiency Below Threshold (Bank 1)

Illuminated Check Engine Light (steady) • Rotten egg / sulfur odor from exhaust

5 Step DIY GuideTroubleshoot

P0171Medium Severity

Est. DIY: $80 - $350 (DIY: $15 - $70)

P0171: System Too Lean (Bank 1)

Check Engine Light on • Rough idling or engine hesitation on acceleration

5 Step DIY GuideTroubleshoot

P0128Low Severity

Est. DIY: $120 - $300 (DIY: $25 - $60)

P0128: Coolant Temperature Below Thermostat Regulating Temperature

Check Engine Light • Cabin heater takes too long to warm up

5 Step DIY GuideTroubleshoot

P0455Low Severity

Est. DIY: $15 - $250 (DIY: $15 - $50)

P0455: Evaporative Emission Control System Leak Detected (Gross Leak)

Check Engine Light on • Gas cap loose warning message on dashboard

5 Step DIY GuideTroubleshoot

P0101Medium Severity

Est. DIY: $45 - $220 (DIY Clean: $12)

Mass Air Flow (MAF) Sensor Circuit Range/Performance

Check Engine Light (CEL) illuminated • Rough or erratic engine idle

4 Step DIY GuideTroubleshoot

P0135Low to Medium Severity

Est. DIY: $80 - $240 (DIY Sensor: $45)

O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)

Check Engine Light on • Slightly increased fuel consumption on short trips

3 Step DIY GuideTroubleshoot

P0172Medium Severity

Est. DIY: $30 - $280 (DIY Clean: $15)

System Too Rich (Bank 1) - Symptoms, Causes & Step-by-Step Fix

Check Engine Light on • Strong unburnt fuel odor from exhaust

3 Step DIY GuideTroubleshoot

P0442Low Severity

Est. DIY: $25 - $200 (DIY: $15)

EVAP System Small Leak Detected - Diagnosis & Repair Guide

Check Engine Light on • Intermittent faint fuel odor near rear wheel well

3 Step DIY GuideTroubleshoot

P0507Medium Severity

Est. DIY: $40 - $250 (DIY Throttle Relearn: $0)

Idle Control System RPM Higher Than Expected - Diagnosis

Engine idles at 1,000+ RPM in park/neutral • RPM surges or hunts at red lights

3 Step DIY GuideTroubleshoot

P0010Moderate Severity

Est. DIY: $120 - $350 (DIY: $40 - $80)

P0010: Camshaft Position Actuator Circuit / Open (Bank 1)

System alert or indicator light illuminated (P0010) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot

P0011High Severity

Est. DIY: $150 - $450 (DIY: $50 - $120)

P0011: Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)

System alert or indicator light illuminated (P0011) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot

P0012High Severity

Est. DIY: $150 - $450 (DIY: $50 - $120)

P0012: Camshaft Position - Timing Over-Retarded (Bank 1)

System alert or indicator light illuminated (P0012) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot

P0013Moderate Severity

Est. DIY: $120 - $320 (DIY: $40 - $75)

P0013: Exhaust Camshaft Position Actuator Circuit / Open (Bank 1)

System alert or indicator light illuminated (P0013) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot

P0014High Severity

Est. DIY: $150 - $420 (DIY: $45 - $90)

P0014: Exhaust Camshaft Position Timing Over-Advanced (Bank 1)

System alert or indicator light illuminated (P0014) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot

P0016Critical Severity

Est. DIY: $300 - $1,200 (DIY: $80 - $250)

P0016: Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor A)

System alert or indicator light illuminated (P0016) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot

P0017Critical Severity

Est. DIY: $300 - $1,200 (DIY: $80 - $250)

P0017: Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor B)

System alert or indicator light illuminated (P0017) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot

P0100Moderate Severity

Est. DIY: $100 - $300 (DIY: $15 - $80)

P0100: Mass or Volume Air Flow Circuit Malfunction

System alert or indicator light illuminated (P0100) • Intermittent performance throttling or unexpected operation halts

5 Step DIY GuideTroubleshoot

Technical FAQ

Frequently Asked Questions

Where is the OBD-II diagnostic port located on the Audi A4?

On the Audi A4 (2020–2026), the standard 16-pin DLC port is located: Under driver side dashboard near hood release lever (pink/purple port). It supports SAE J1979 / ISO 15765-4 CAN protocols for all handheld OBD-II code readers.

What are the most common Check Engine fault codes on the Audi A4?

The most frequently logged trouble codes on the Audi A4 (2.0L TFSI Turbo 4-Cyl (EA888 Gen 4 201HP–261HP)) include P0420, P0171, P0300, P0299.

How much does an OBD-II diagnostic scan cost for a Audi A4?

Most auto parts retailers (AutoZone, O'Reilly, Advance Auto) offer basic code reading free of charge. Dealership diagnostic scan fees average $120 to $180 based on Audi's standard $170/hr labor rate.