Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

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Engine Speed (RPM) Signal, Checking




Engine Speed (RPM) Signal, Checking

NOTE: The engine speed signal is taken from contact 37 on the engine control module. The signal is used for various functions including the rev counter display on the instrument cluster.

- Connect test box VAG 1598/31 to wiring harness for engine control module. Do not connect to the engine control module itself.

- Test for open circuit and short to positive or Ground in the following wiring connection:

Test box VAG 1598/31 Socket Instrument cluster
Socket Contact
37 See Electrical Wiring Diagrams, Troubleshooting & Component Locations

- Correct short circuit or open circuit if necessary.