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Audi A4 B6 Quattro 1.8T OBD2 Codes P2123 and P2128: No Throttle Response After Fan Sensor Workaround

Model: Audi A4 B6 Quattro 1.8T Fault Code: P2123 Posted: 2018-04-26 15:47

I own an Audi A4 B6 Quattro 1.8T and am experiencing a critical issue after attempting to troubleshoot a radiator fan problem. The mechanic advised disconnecting the sensor wire from the lower radiator hose and jumping it to test if the fan activates — this did not work. After starting the vehicle, I notice no throttle response: pressing the accelerator pedal has no effect. The car now displays OBD2 diagnostic codes P2123 and P2128. These codes return immediately after clearing them via a scan tool. I've already tried disconnecting the battery for several hours to reset the ECU, but the issue persists. I have replaced both the throttle body and the gas pedal with no improvement. No visible wiring damage or loose connections are present in the throttle or related circuits. Given that this vehicle is currently non-operational, should I proceed with replacing the ECU? Are there any other diagnostic steps before considering such a costly repair? I'm concerned about whether my wife's car can safely be driven again — especially given the lack of response from the accelerator pedal and recurring error codes.

Related fault codes
P2123P2128
Comments (2)
Anonymous 2018-04-27 06:22

Check for blown fuses, particularly in the main fuse panel or hidden fuse locations. Refer to official wiring diagrams for your Audi A4 B6 Quattro 1.8T model — resources like bbbind.com provide detailed schematics and fuse layouts.

Anonymous 2018-04-27 10:25

The issue may stem from a specific circuit or module, not just the main fuse panel. There are several hidden fuses located in various areas of the vehicle (e.g., under the hood, near the steering column), so it's important to verify all possible fuse locations before assuming ECU failure.