Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2001 Audi A4 Quattro, 2.8 H, AutomaticFACTORY OEM SERVICE PROCEDURE
A4 & S4
- Check engine timing fuses in fuse box, replace as necessary. Ensure battery voltage is 11.7 volts or more. Charging system tests okay. Disconnect Engine Control Module (ECM) harness connector. In A4 and S4 models, ECM is located in left rear corner of engine compartment, in electronics box. Connect VAG 1598/31 test box to ECM harness connector (leave ECM disconnected). Turn ignition on. Using DVOM, measure voltage between specified VAG test box sockets. See CHECKING ENGINE CONTROL MODULE VOLTAGE SUPPLY
table. If voltage is not as specified, go to next step. If voltage is as specified, go to step 3
.CHECKING ENGINE CONTROL MODULE VOLTAGE SUPPLY
Between VAG Test Box Sockets Specification 2 & 3 Battery Voltage 1 & 3 Battery Voltage 2 & 62 Battery Voltage - Check for open, short to ground or short to voltage in suspect circuit between ECM and ECM voltage supply relay. See WIRING DIAGRAMS article. To test ECM power supply relay, go to ENGINE CONTROL MODULE POWER SUPPLY RELAY . If problem is found, repair as necessary. After repair go to next step.
- Using scan tool, clear DTCs and generate a ECM readiness code. See FUNCTION 05 - CLEARING DIAGNOSTIC TROUBLE CODES and READINESS CODE under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. Test drive vehicle. Using scan tool, retrieve DTCs. If DTC does not reset, testing is complete.
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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