Initial Inspection and Diagnostic Overview

Motronic ECM Location:

Control units are known to be the cause of various customer DRIVEABILITY complaints. Various campaigns which may include control unit replacement, and system modifications have been implemented by Volkswagen to remedy this situation. Always refer to TECHNICAL SERVICE BULLETINS for the latest information concerning DRIVING PERFORMANCE.

CAUTION: Always turn the ignition switch "OFF" before changing meter ranges, and before disconnecting or connecting the meter probes. Doing so with the ignition switch turned "ON" risks permanent control unit damage.
- If a problem is not remedied after completing the test procedures in ECM Pinout Tests, the control unit may be defective. Replace the control unit with a "KNOWN GOOD" unit and retest as necessary.

NOTE: Because of its adaptive capability, the Motronic control unit MUST be returned to its reference settings IF:
- The Engine Coolant Temperature (ECT) Sensor (blue connector) has been disconnected while the engine is running.
- Any of these components have been replaced:
Motronic control unit
Mass Air Flow Sensor
Throttle Position Sensor
Throttle body