Engine Speed Sensor Checking

NOTE: All voltage and continuity tests should be performed with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless specifically stated differently in testing procedures. For help with diagnostic testing. See WIRING DIAGRAMS .

Location of Engine Speed (RPM) sensor and harness connection. See COMPONENT LOCATIONS .

Disconnect RPM sensor harness connector (Gray sensor and harness). See Figure.
Using DVOM, switched to resistance range. Connect DVOM to terminals No. 1 and 2, using jumper leads from (VW1594). See Figure. Resistance must be approximately 1000 ohms.
If resistance is not correct, replace RPM sensor. If YES: Connect DVOM between terminals No. 1 and 3 and then terminals No. 2 and 3. Both must be infinite ohms (open). If NO: Replace RPM sensor.
If resistance is correct, check wiring between sensor harness connector and Engine Control Module (ECM) harness connector. Connect (VAG 1598) test box to ECM harness connector using (VAG 1598/5) adaptor cable. See CONNECTING VAG 1598 TEST BOX . ECM is not connected.
Check the following terminal for continuity and/or short circuit(s):
- Between sensor harness connector terminal No. 1 and test box socket 48.
- Between sensor harness connector terminal No. 2 and test box socket 49.
- Between sensor harness connector terminal No. 3 and test box socket 19 (ground). See Figure.
If necessary repair open circuit or shorted wires between sensor harness connector and the ECM connector (terminals No. 48, 49 and 19). See WIRING DIAGRAMS .
If circuit is okay, visually check teeth on starter ring gear. Remove bracket with RPM sensor and Crankshaft Position (CKP) sensor and inspect. Rotate engine slowly and examine ring gear for runout and broken and/or damaged teeth, replace if necessary. If ring gear is okay, replace the ECM. See ECM IDENTIFICATION and ECM CODING under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS article.