The 2003 Audi A4 utilizes a J293 Coolant Fan Control (FC) module to manage the electric cooling fan. This module, positioned above the fan itself, lacks diagnostic capabilities and doesn’t communicate with Vcds-lite Release 1.2 Serial or any VCDS version. However, understanding the system and using alternative methods can help pinpoint issues.
The Engine Control Module (ECM), designated as J220, connects to the J293 via a signal wire. This wire transmits a Pulse Width Modulated (PWM) signal from the ECM to activate the fan. While VCDS-Lite release 1.2 serial won’t directly interact with the fan control module, it can be used to diagnose related ECM functions.
An Output Test performed on the ECM (with the key on and engine off) should reveal a gradual increase in fan speed from 0% to 100% and then back to 0%. This test helps verify the ECM’s ability to command the fan.
If the fan remains unresponsive, check Measuring Value Block (MVB) Group 135, field 2, within the ECM data. This field displays the current fan output speed as a percentage. Additionally, MVB-137 provides insights into the AC system’s status and requests, potentially illuminating related problems.
Should these checks prove inconclusive, verify fuses S4 (5 amp) located on the dashboard’s left side and S42 (40/60 amp) positioned above the relay panel in the dash.
If the fuses are intact, examine the signal from the ECM to the J293 using an oscilloscope for a precise reading. A Digital Volt-Ohm Meter (DVOM) set to AC voltage might detect some voltage, but this only represents Root Mean Square (RMS) voltage and not the complete PWM signal.
Absence of an ECM signal necessitates checking the wiring between the ECM and J293, specifically the red/white wire.
If voltage and signal reach the J293 but the fan remains inactive, the J293 module itself is likely faulty. In this case, replacement of the J293 module would be the necessary course of action. While VCDS-Lite release 1.2 serial cannot directly diagnose the J293, it plays a crucial role in eliminating other potential causes within the cooling system.
