Reference Low

The reference low circuit establishes a common ground between the ignition control module (ICM) and the PCM. The circuit minimizes electrical ground differences between the PCM and the ICM. The PCM uses the reference low circuit to clearly recognize the 3X and 18X reference signals. A malfunction in the reference low circuit may result in a reduced driveability condition and possibly a malfunction indicator lamp (MIL) activation with no DTC set.