Tachometer on MM systems

December 30, 2002
Code 35 on Magnetti-Marelli EFI Systems
Normally a code 35 is set when there is a problem in the tachometer circuit. We
have identified another possible cause for a code 35 not specifically covered in the
Service Manuals. It pertains to a current or recurring historic code 35 (Tachometer)
on 1995-2001 EFI Touring models including Road Kings not normally equipped with
a tachometer. This code may be accompanied by codes 41, 42 or 56 and perhaps
even hard starting, poor cold idle and driveability issues. The ECM is functional
because it still has Key On power at pin 26.
Diagnosing this possible condition is relatively easy. Using the Scanalyzer, look for
consistent battery voltage in the data monitor mode (you may have to perform a
wiggle test while monitoring) because the Scanalyzer is monitoring voltage at pin 35
of the ECM (not battery voltage across the battery terminals). Closely inspect every
connection from the Main Circuit breaker to the ECM for loose crimps or
connections. Even a loose ECM fuse or intermittent ECM relay can cause this
condition.