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.
SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSAUDI1998A4 AVANT QUATTRO, AUTOMATICREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - INTRODUCTIONMIL CHECKA4
1998 Audi A4 Avant Quattro, Automatic
Mil Check: A4
1998 Audi A4 Avant Quattro, AutomaticSECTION A4
- Turn ignition on. MIL should light. If MIL lights, go to step 5). If MIL does not light, go to next step.
- MIL is not lighting due to faulty wiring or an open circuit. Turn ignition off. Disconnect Powertrain Control Module (PCM) connectors. PCM is located in left rear corner of engine compartment inside electrical box. Connect VAG 1598/22 test box to PCM wiring harness. See Figure .
- Connect a jumper wire between test box sockets No. 2 and 17. Turn ignition on. MIL should light. If MIL does not light, go to next step.
- Turn ignition off. Inspect MIL bulb. If bulb is okay, check for an open circuit between MIL and PCM. See WIRING DIAGRAMS article. If wiring is okay, replace faulty PCM. See PCM REPLACING .
- Start engine and let it idle. MIL should go out after a few seconds. If MIL goes out, MIL is functioning properly. If MIL does not go out, check for any stored DTCs. See RETRIEVING CODES under SELF-DIAGNOSTIC SYSTEM. If DTCs are stored, repair as necessary. If no DTCs are stored, go to next step.
- MIL is on continuously due to a short to ground. Turn ignition off. Disconnect Powertrain Control Module (PCM) connectors. Connect VAG 1598/22 test box to PCM wiring harness. See Figure .
- Connect a DVOM between test box socket No. 17 and ground. DVOM should indicate infinity (no resistance). If DVOM reading is not as specified, go to next step. If DVOM reading is as specified, go to step 9).
- Check for a short circuit between MIL and Powertrain Control Module (PCM). See WIRING DIAGRAMS article.
- If no continuity is present and there is no short to ground, replace faulty PCM. See PCM REPLACING .
RENDER: 1.0x
NO RELATED
Recommended Tools & Savings
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.