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
If it fails:
lemon-manuals.org.ua
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Reference Low (PCM Digital RPM Counter)
This is a ground circuit for the digital RPM counter inside the
PCM, but the wire is connected to engine ground only through the
ignition control module. Although this circuit is electrically connected to the PCM, it is not connected to ground at the PCM. The PCM compares voltage pulses on the 18X and 3X reference input circuits to any on this circuit, ignoring pulses that appear on both. If the circuit is open, or connected to ground at the PCM, it may cause poor engine performance and possibly a MIL with no DTC set.