Diagnostic Aids
Scan tester should indicate a vehicle speed whenever the drive wheels are turning faster than 3 MPH. Check circuit No. 437 for proper connections. Ensure wire connector is clean and tight and harness is routed correctly. A problem in circuit No. 437 will not affect the VSS input or scan tester readings. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.