DTC 16

Code 16 Chart:

Code 16 Wiring Diagram:

Circuit Description:

The ignition module sends a reference signal to the ECM twice per revolution to indicate crankshaft position and rpm so that the ECM can determine when to pulse the ignition coils and control ignition timing. This signal is called the 2X reference because it occurs two times per revolution. The ignition module applies 5 volts from terminal "H" through CKT 430 to ECM terminal "BD8" and in effect, switches this circuit to ground for a very short period of time. Code 16 is set if the ECM receives 1X reference pulses with no 2X reference pulses.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. This determines if the ECM recognizes a problem. If it doesn't set Code 16 at this point, the problem is intermittent and could be due to a loose connection. See "Diagnostic Aids."

2. This step simulates the 2X signal. The ECM should recognize the drop in voltage as the test light probe is removed, if the circuit and ECM are OK. This step will give accurate results only if the chart sequence is used - ignition "OFF," ignition "ON," Scan tool set to 2X reference and terminal "G" touched with test light probe.

3. If the ECM did not recognize the simulation of the 2X signal, CKT 430 may be open or shorted to ground or voltage. If CKT 430 is OK, the ECM is faulty.

4. Step 2 indicated that CKT 430 is OK and the ECM is capable of recognizing the simulated 2X reference pulse. This indicates either a poor connection at ignition module terminal "H" or a faulty ignition module caused the Code 16.

Diagnostic Aids:


An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect ECM harness connector terminal "BD8" and ignition module terminal "H" for improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.