Code 16 - Missing 2X Reference Circuit (2.3L): Notes

Ignition module sends a reference signal to ECM twice per revolution to indicate crankshaft position and RPM so ECM can determine when to pulse ignition coils and control ignition timing. This signal is called "2X" reference because it occurs twice per crankshaft revolution. Ignition module applies 5 volts to 2X circuit, which is monitored by ECM. Ignition module toggles this signal to ground twice per crankshaft revolution. Code 16 will set if ECM detects 1X reference signals with no 2X pulses.

1. Determines if ECM recognizes a problem. Problem is intermittent and could be due to a loose connection if ECM does not set Code 16 at this point.
2. This step simulates a 2X signal. ECM should recognize drop in voltage as test light probe is removed. This step will give accurate results only if proper sequence is used. Turn ignition off, turn ignition on, scan 2X reference while touching and removing test light connected to battery voltage to terminal "H" of ignition module harness.
3. If ECM did not recognize simulation of 2X signal, circuit may be open or shorted to ground between ignition module harness connector and ECM. If circuit is okay, ECM is faulty.
4. Step 2) indicated 2X reference circuit was okay and ECM is capable of recognizing a simulated 2X signal. This indicates either a poor connection or a faulty ignition module caused Code 16.