2003 Audi A4 (1.6 ALZ) - MIL activated - Fault codes: P0300, P0301, P0304, P0134, P0420

[evenkg]

Hi guys!

I have a 2003 model Audi A4 with the 102hp 1.6L petrol engine. The car has done 170K km, and has been regularly serviced. I've been having intermittent issues lately regarding powerloss (with flashing MIL), and constant MIL when driving longer trips. I have reset the fault codes with my diagnostic tool (Launch Diagun X431), and can drive for a couple of days without any issues, and suddently the car losses all power and MIL is flashing when driving.

The following DTC's came up at first readout:

P1118 - H02S HEATER CIRCUIT BANK 1 - SENSOR 2.
P0172 - SYSTEM TOO RICH BANK 1 - OUTPUT DOES NOT HAVE A CONTACT/SHORT
P0134 - O2 SENSOR CIRCUIT BANK 1, SENSOR 1 - NO ACTIVITY DETECTED
P0300 - MULTIPLE CYLINDRE MISFIRE DETECTED
P0301 - CYLINDER 1 MISFIRE DETECTED - SPORADIC SHORT CIRCUIT TO ANOTHER VALVE
P0304 - CYLINDER 4 MISFIRE DETECTED - SPORADIC SHORT CIRCUIT TO ANOTHER VALVE

After this readout I figured out that there is a problem with the HO2-sensor and ignition system, so i replaced and checked the following:

Fuses checked - found OK
Wiring checked - found OK
Exhaust system checked - found OK
Spark plugs replaced x4
Front and back HO2 sensors replaced.
Fault codes erased and adaptive values are reset.

After this the car was running fine for two days, and the symptoms mentioned above returned (powerloss / MIL flashing). The following DTCs returned at secound readout:

P0420 - CATALYST SYSTEM - EFFICIENCY BELOW THRESHOLD
P0134 - O2 SENSOR CIRCUIT BANK 1, SENSOR 1 - NO ACTIVITY DETECTED
P0300 - MULTIPLE CYLINDRE MISFIRE DETECTED
P0301 - CYLINDER 1 MISFIRE DETECTED - SPORADIC SHORT CIRCUIT TO ANOTHER VALVE
P0304 - CYLINDER 4 MISFIRE DETECTED - SPORADIC SHORT CIRCUIT TO ANOTHER VALVE

I have attached the wiring diagram for the ECU (Simos 3.4), and there is no common wires/connections/fuses for ignition and emission control system.

Anybody out there who have any idea of what is causing this problem?


Best regards
Even

[arman123]

Check the earth wire located behind the passenger headlight lossen it give it a clean and see if it makes it better.don't really know much about the engine but found this solution online and it might work