Audi Diagnostic Trouble Codes
Common OBD2 fault codes found on Audi vehicles with model-specific causes, known issues, TSBs, and adjusted repair cost estimates. Each guide is tailored for Audi owners.
Emissions
Camshaft Position B - Timing Over-Advanced or System Performance (Bank 1)
Audi A4 • 2008-2024
On the Audi A4, the EA888 1.8 TFSI and 2.0 TFSI engines are well known for timing chain tensioner an...
"B" Camshaft Position - Timing Over-Retarded (Bank 1)
Audi A4 • 2008-2024
The 2.0 TFSI (EA888) engine uses an exhaust camshaft adjuster that can fail due to oil sludge or a w...
"A" Camshaft Position - Timing Over-Advanced or System Performance (Bank 2)
Audi A6 • 2005–2024
The A6 3.0 TFSI EA837 supercharged V6 commonly sets P0021 around 100,000 to 150,000 km due to bank 2...
"A" Camshaft Position - Timing Retarded (Bank 2)
Audi A6 • 2005–2024
The A6 3.0 TFSI EA837 supercharged V6 is the prime P0022 candidate. Bank 2 intake adjuster failure o...
O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
Audi A4 • 2008-2024
The A4 shares the EA888 family with the Golf, so the upstream Bosch sensor lives in the hot turbo do...
O2 Sensor Circuit Malfunction (Bank 1, Sensor 2)
Audi A4 • 2006–2024
On the B7 and B8 A4 with the 2.0 TFSI (EA113 and EA888), carbon buildup on the intake valves causes ...
O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
Audi A4 • 2006–2024
The B7 and B8 A4 with 2.0 TFSI shares the EA113/EA888 oil consumption issue plus carbon buildup on t...
O2 Sensor Circuit High Voltage (Bank 1, Sensor 2)
Audi A4 • 2006–2024
The B7 and B8 A4 with 2.0 TFSI is notorious for HPFP wear (especially early EA113), which raises fue...
O2 Sensor Circuit Slow Response (Bank 1, Sensor 2)
Audi A4 • 2006–2024
The B7 and B8 A4 with 2.0 TFSI shares the EA888 oil consumption pattern. Carbon buildup on intake va...
O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)
Audi A4 • 2006–2024
On the B7 and B8 A4 with 2.0 TFSI, the downstream sensor connector lives in a tight spot near the ge...
Exhaust Gas Recirculation (EGR) Flow Insufficient
Audi A4 • 2005-2024
The A4 shares VW Group TDI and TFSI hardware, so the 2.0 TDI is the most common P0401 vehicle here, ...
Exhaust Gas Recirculation Flow Excessive Detected
Audi A4 • 2008–2024
The A4 2.0 TDI (B8 and B9 chassis) shares EA189 and EA288 engines with the Golf and suffers identica...
Exhaust Gas Recirculation Control Circuit Malfunction
Audi A4 • 2008–2024
B8 and B9 A4 2.0 TDI models share the EA189/EA288 EGR valve with the Golf, so failure modes are iden...
Exhaust Gas Recirculation Control Circuit Range/Performance
Audi A4 • 2008–2024
The A4 2.0 TDI (B8, B9) shares the EA189 and EA288 EGR setup with the Golf, so P0404 has identical r...
Exhaust Gas Recirculation Sensor "A" Circuit Low
Audi A4 • 2008–2024
B8 and B9 A4 2.0 TDI models share the EGR sensor failure modes with the Golf. The B8 has tighter pac...
Exhaust Gas Recirculation Sensor "A" Circuit High
Audi A4 • 2008–2024
B8 and B9 A4 2.0 TDI suffer the same P0406 failure modes as the Golf, plus restricted access due to ...
Exhaust Gas Recirculation Sensor "B" Circuit Low
Audi A4 • 2010–2024
P0407 is most common on the A4 3.0 TDI V6 (CCWA, CTBA, CAPA codes), which uses two EGR valves with t...
Exhaust Gas Recirculation Sensor "B" Circuit High
Audi A4 • 2010–2024
P0408 on the A4 3.0 TDI V6 (CCWA, CTBA, CAPA codes) means the bank-2 EGR position sensor has failed ...
Secondary Air Injection System Malfunction
Audi A4 • 2005-2020
The 2.0 TFSI in the B7 and B8 A4 shares the VW secondary air system. The combination valve is the mo...
Secondary Air Injection System Incorrect Flow Detected
Audi A3 • 2005-2024
The A3 uses the same MQB platform secondary air system as the Golf on 2013+ models. The 2.0 TFSI in ...
Warm Up Catalyst Efficiency Below Threshold (Bank 1)
Audi A6 • 2005-2024
The Audi A6 3.0 TFSI (EA837 supercharged V6) and 3.0 TDI V6 both have separate pre-cats per bank, an...
Main Catalyst Efficiency Below Threshold (Bank 1)
Audi A6 • 2005-2024
The Audi A6 3.0 TFSI (EA837) and 3.0 TDI run separate main cats per bank. On Bank 1 (passenger side)...
Heated Catalyst Efficiency Below Threshold (Bank 1)
Audi A6 • 2019-2024
The C8 Audi A6 with the 3.0 TFSI (EA839) V6 mild-hybrid uses a heated catalyst on Bank 1 to meet Eur...
Heated Catalyst Temperature Below Threshold (Bank 1)
Audi A6 • 2019-2024
The C8 A6 3.0 TFSI (EA839) V6 mild-hybrid sets P0424 most often after winter storage when the 48V ba...
Catalyst System Efficiency Below Threshold (Bank 2)
Audi A4 • 2005-2024
Four-cylinder TFSI A4 models are single-bank and rarely see P0430. The fault is most relevant on the...
Warm Up Catalyst Efficiency Below Threshold (Bank 2)
Audi A6 • 2005-2024
On the Audi A6 3.0 TFSI (EA837 supercharged V6) and 3.0 TDI V6, P0431 points to the Bank 2 (driver s...
Main Catalyst Efficiency Below Threshold (Bank 2)
Audi A6 • 2005-2024
On the Audi A6 3.0 TFSI (EA837) and 3.0 TDI V6, P0432 typically appears at 180,000 km on the Bank 2 ...
Heated Catalyst Efficiency Below Threshold (Bank 2)
Audi A6 • 2019-2024
The C8 Audi A6 3.0 TFSI (EA839 V6 mild-hybrid) and 3.0 TDI mild-hybrid both use a heated catalyst on...
Heated Catalyst Temperature Below Threshold (Bank 2)
Audi A6 • 2019-2024
The C8 A6 3.0 TFSI (EA839 V6 mild-hybrid) and 3.0 TDI mild-hybrid set P0434 most often after winter ...
O2 Sensor Signal Biased/Stuck Lean (Bank 1, Sensor 1)
Audi A4 • 2008-2024
The 2.0 TFSI A4 shares the lean-code tendency of the wider VAG range. PCV diaphragm failure and a cr...
Ignition
Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor B)
Audi A6 • 2005–2024
The 3.0 TFSI EA837 supercharged V6 in the A6 is known for camshaft adjuster and timing chain tension...
Crankshaft Position - Camshaft Position Correlation (Bank 2 Sensor A)
Audi A6 • 2005–2024
The 3.0 TFSI EA837 supercharged V6 and the 4.2 FSI V8 are the typical P0018 candidates in the A6 lin...
Crankshaft Position - Camshaft Position Correlation (Bank 2 Sensor B)
Audi A6 • 2005–2024
The A6 3.0 TFSI EA837 supercharged V6 sets P0019 frequently around 100,000 to 150,000 km. The bank 2...
Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor)
Audi A4 • 2008-2024
B8 A4 with the 2.0 TFSI tends to log P0328 from harness chafing near the engine cover mounting bolt....
Camshaft Position Sensor Circuit Malfunction
Audi A4 • 2008-2024
The Audi A4 shares the EA888 2.0 TFSI and the 3.0 TFSI V6 with much of the VAG range. CMP sensors ar...
Camshaft Position Sensor "A" Circuit Range/Performance
Audi A4 • 2005-2024
The 2.0 TFSI in B7 and early B8 A4s uses a timing chain at the rear of the engine, making replacemen...
Camshaft Position Sensor "A" Circuit Low Input (Bank 1 or Single Sensor)
Audi A4 • 2008-2024
B8 A4 with the 2.0 TFSI commonly sets P0342 alongside P0011/P0012 when the cam adjuster oil control ...
Camshaft Position Sensor "A" Circuit High Input (Bank 1 or Single Sensor)
Audi A4 • 2008-2024
B8 A4 with 2.0 TFSI sometimes logs P0343 after a heat-soak start. The cam sensor fails intermittentl...
Fuel System
Mass or Volume Air Flow Circuit Low Input
Audi A4 • 2008–2024
B8 A4 2.0 TFSI is notorious for MAF failures around 100,000 km. The Bosch hot-film element loses sen...
Mass or Volume Air Flow Circuit High Input
Audi A4 • 2008–2024
B8 A4 2.0 TFSI shares the EA888 MAF setup with the Golf and exhibits identical P0103 patterns. Restr...
System Too Lean (Bank 1)
Audi A4 • 2008-2024
The A4 shares the EA888 family with the Golf, so the PCV and oil separator diaphragm is the prime P0...
System Too Rich (Bank 1)
Audi A4 • 2008-2024
The 2.0 TFSI EA888 in the B8 and B9 A4 shares the VW purge valve weakness and is also prone to carbo...
Fuel Trim Malfunction (Bank 2)
Audi A6 • 2011-2024
C7 A6 with the EA837 3.0 TFSI V6 has well-documented Bank 2 fuel trim issues. The supercharger meter...
System Too Lean (Bank 2)
Audi A4 • 2005-2024
Four-cylinder TFSI A4 models are single-bank and set P0171; P0174 shows up on the V6 cars such as th...
System Too Rich (Bank 2)
Audi A6 • 2011-2024
C7 A6 with the 3.0 TFSI sometimes logs P0175 when the EVAP purge valve sticks open and feeds extra v...
Intake Manifold Runner Control Stuck Open (Bank 1)
Audi A4 • 2005-2024
The A4 B7 and B8 with the 2.0 TFSI engine shares the same intake manifold design as the Golf and is ...
Intake Manifold Runner Control Stuck Closed (Bank 1)
Audi A3 • 2004-2024
The A3 shares its engine and intake manifold with the VW Golf. The 2.0 TDI (BKD/BMM engine codes) in...
Intake Manifold Runner Position Sensor/Switch Circuit Range/Performance (Bank 1)
Audi A3 • 2008-2024
The A3 8P and 8V with 2.0 TDI engines share the same intake manifold as the Golf. The A3 2.0 TDI is ...
System Too Lean at Idle (Bank 1)
Audi A3 • 2005-2024
The A3 with 1.4 TFSI and 2.0 TFSI engines shares the same PCV and vacuum leak issues as the VW Golf....
Cooling System
Electrical
Engine Overspeed Condition
Audi A3 • 2008-2024
Shares the DSG/S-tronic transmission with the VW Golf. P0219 on automatic A3 models is usually DSG-r...
Knock Sensor 1 Circuit Low Input (Bank 1 or Single Sensor)
Audi A4 • 2005–2024
The B8 A4 with the 2.0 TFSI EA888 has knock sensors mounted under the intake manifold, similar to V6...
Glow Plug / Heater Circuit "A" Malfunction
Audi A4 TDI • 2004-2019
The A4 TDI shares VAG glow plug architecture with the Golf and uses a monitoring control module. P03...
Brake Switch "A"/"B" Correlation
Audi A4 • 2008-2024
B8 A4 owners frequently report P0504 from a sticking brake switch plunger. The plastic plunger swell...
ECM/PCM Processor Fault
Audi A4 • 2005-2024
B7, B8, and B9 A4 models use Simos and MED17 ECUs that can log P0606 after voltage problems, so chec...
Glow Plug Control Module Circuit
Audi A4 TDI • 2004-2019
The A4 TDI shares the VAG monitoring control module with the Golf and Passat. P0670 typically points...
Cylinder 1 Glow Plug Circuit
Audi A4 TDI • 2004-2019
The A4 TDI uses the same VAG per-plug monitoring as the Golf, so P0671 isolates cylinder 1. Some 2.0...
Cylinder 2 Glow Plug Circuit
Audi A4 TDI • 2004-2019
The A4 TDI uses the same VAG per-plug monitoring as the Golf, so P0672 isolates cylinder 2. Some 2.0...
Cylinder 3 Glow Plug Circuit
Audi A4 TDI • 2004-2019
The A4 TDI uses the same VAG per-plug monitoring as the Golf, so P0673 isolates cylinder 3. Some 2.0...
Cylinder 4 Glow Plug Circuit
Audi A4 TDI • 2004-2019
The A4 TDI uses the same VAG per-plug monitoring as the Golf, so P0674 isolates cylinder 4. Some 2.0...
Intake Manifold Runner Control Circuit/Open (Bank 1)
Audi A4 • 2005-2024
The A4 B7/B8 with the 2.0 TFSI engine has the actuator connector in a particularly tight location th...
Misfire
Random/Multiple Cylinder Misfire Detected
Audi A4 • 2008-2024
The A4 shares the EA888 family with the Golf, so intake-valve carbon on direct-injection 2.0 TFSI en...
Cylinder 1 Misfire Detected
Audi A4 • 2008-2024
The A4 shares the EA888 TSI family with VW, so cylinder-1 misfires often trace to intake-valve carbo...
Cylinder 2 Misfire Detected
Audi A4 • 2005-2024
The 2.0 TFSI (EA888) engine in B8 and B9 A4 models is prone to carbon buildup on intake valves due t...
Cylinder 6 Misfire Detected
Audi A6 • 2011-2024
C7 A6 with the 3.0 TFSI supercharged V6 sometimes triggers P0306 from cylinder 6 injector wear or a ...
EVAP System
Evaporative Emission Control System Malfunction
Audi A4 • 2005–2024
The B7 and B8 A4 with the 2.0 TFSI EA888 engine commonly trigger P0440 due to the N80 purge valve cl...
Evaporative Emission Control System Vent Control Circuit Open
Audi A4 • 2005–2024
The B7 and B8 A4 share EVAP components with the VW Golf. The N115 vent valve on the canister is the ...
Evaporative Emission Control System Vent Control Circuit Shorted
Audi A4 • 2005–2024
The B7 and B8 A4 share the underbody harness routing with the VW Golf. P0448 on these vehicles often...
Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction
Audi A4 • 2005–2024
B7 and B8 A4 share the N115 vent valve with the VW Golf, but the harness routing on the A4 sedan is ...
Evaporative Emission Control System Pressure Sensor Intermittent
Audi A4 • 2005–2024
B7 and B8 A4 use a fuel pump module with integrated FTP sensor. Replacement requires removing the re...
Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off)
Audi A4 • 2005–2024
B7 and B8 A4 share the bayonet-style cap with the VW Golf. P0457 is one of the most common codes set...
Transmission
Input/Turbine Speed Sensor Circuit Malfunction
Audi A4 • 2005-2024
The A4 with Multitronic CVT (B7/B8) and S-Tronic DSG uses speed sensors that can fail due to metalli...
Torque Converter Clutch Circuit Performance/Stuck Off
Audi A4 • 2005-2024
The B8 and B9 A4 with the ZF 8HP and earlier Aisin transmissions are susceptible to P0741. On the Mu...
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