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)
Or, hide this message:
temporarily or
permanently
Reference Low
This is a ground circuit for the digital RPM counter inside the
PCM, but the wire is connected to engine ground through the ICM only. Although this circuit is electrically connected to the PCM, the circuit is not connected to ground at the PCM. The PCM compares the voltage pulses on the 18X and the 3X reference input circuits to any on the reference low circuit, and ignores pulses that appear on both circuits. If the circuit is open, or connected to ground at the PCM, reduced engine performance and
MIL illumination with no DTC set may result.