Engine Controls - Self-Diagnostics - Introduction: Diagnosis Audi A4 B5 facelift

SELF-DIAGNOSTIC SYSTEM

Note. It is necessary to generate a PCM readiness code if PCM memory is cleared, battery voltage is disconnected or PCM is disconnected. See CLEARING DIAGNOSTIC TROUBLE CODES . If PCM was replaced, see PCM REPLACEMENT .

DIAGNOSTIC TROUBLE CODES

The Powertrain Control Module (PCM) can identify malfunctions and store them in memory in the form of a Diagnostic Trouble Code (DTC). DTCs are stored until memory is erased. If positive battery cable or PCM connector is disconnected, DTCs are erased.

RETRIEVING DIAGNOSTIC TROUBLE CODES

Note. If Malfunction Indicator Light (MIL) is on continuously and no DTCs are stored, perform MIL check. See MIL CHECK. If MIL never illuminates, see MIL CHECK.

VISUAL INSPECTION

Prior to retrieving Diagnostic Trouble Codes (DTCs), perform a comprehensive visual inspection of ground connections located on intake manifold, ensure battery negative cable is okay, and check ground cable between engine and vehicle body. Repair as necessary. Check vacuum hoses for breakage and blockage. Check electrical wiring and connectors for damage and corrosion. Repair as necessary.

Note. Manufacturer does not provide procedure for retrieving DTCs without scan tool. If using Volkswagen Audi Group (VAG) 1551 scan tool for diagnosis, follow manufacturer's instructions for operation. VAG 1551 is recommended for diagnosing DTCs.

1. Locate Data Link Connector (DLC) located behind cover under left side of steering column. (Scheme 16) Connect VAG 1551 scan tool or generic scan tool to DLC. Turn ignition on or start engine and let it idle. If engine will not start, crank engine for at least 6 seconds. See appropriate table under «DIAGNOSTIC TROUBLE CODES IDENTIFICATION»(ref-3050-S27199186302000041700000).
2. If no communication is possible with PCM, verify connection for scan tool is okay. If scan tool connection is okay, check wiring harness between DLC and PCM for open or short circuit. See WIRING DIAGRAMS article. Repair as necessary. PCM is located in left rear corner of engine compartment inside electrical box. If wiring harness is okay, PCM is possibly faulty. See «PCM VOLTAGE CHECK»(ref-3050-S10697198612000041700000).

Scheme 16

CLEARING DIAGNOSTIC TROUBLE CODES

Note. It is necessary to generate a PCM readiness code if PCM memory is cleared, battery voltage is disconnected or PCM is disconnected. If PCM was replaced, see PCM REPLACEMENT .

Note. Manufacturer does not provide information for using a generic scan tool to clear codes.

VAG 1551 scan tool is necessary for clearing codes. Follow scan tool prompts for clearing codes. After clearing codes, it is necessary to generate a PCM readiness code. A PCM readiness code resets 8 specific values to zero. Follow scan tool prompts for generating a PCM readiness code.