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.
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HOMESERVICE MANUALSAUDI1999A4 BASE, 1.8 B, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - SELF-DIAGNOSTICS - 1.8L TURBODIAGNOSTIC TESTSDTC P0442/16826 & P0455/16839: EVAP SYSTEM FAILURE
1999 Audi A4 Base, 1.8 B, Automatic
DTC P0442/16826 & P0455/16839: EVAP System Failure
1999 Audi A4 Base, 1.8 B, AutomaticSECTION DTC P0442/16826 & P0455/16839: EVAP System Failure
- Disconnect 3-pin EVAP Leak Detection Pump (LDP) connector. LDP connector is located behind left rear wheel housing liner. Using a DVOM, measure resistance between LDP connector (component side) terminals No. 1 and 3. Resistance should be 640-720 ohms. If resistance is within specification, go to next step. If resistance is not within specification, replace LDP. Erase DTC memory. See CLEARING CODES in SELF-DIAGNOSTICS - INTRODUCTION article.
- Using a DVOM, measure resistance between LDP connector (component side) terminals No. 2 and 3. Resistance should be 17.5-27.5 ohms. If resistance is within specification, go to next step. If resistance is not within specification, replace LDP. Erase DTC memory. See CLEARING CODES in SELF-DIAGNOSTICS - INTRODUCTION article.
- Connect VAG 1527B LED voltage tester between LDP connector (harness side) terminal No. 3 and ground. Start engine and idle. LED voltage tester should illuminate. If LED voltage tester illuminates, system is functioning properly. Test is complete. Erase DTC memory. See CLEARING CODES in SELF-DIAGNOSTICS - INTRODUCTION article.
- If LED voltage tester does not illuminate, check fuse for LDP. Inspect wiring between LPD connector (harness side) terminal No. 3 and fuse for an open circuit. Check fuel pump relay operation. See SYSTEM & COMPONENT TESTING article. Repair as necessary. Erase DTC memory. See CLEARING CODES in SELF-DIAGNOSTICS - INTRODUCTION article.
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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.