DTC 12

Code 12 - No Hall Effect Pulses:

Wiring Diagram for Code 12 - No Hall Effect Pulses:

CODE 12 - NO HALL EFFECT PULSES


Circuit Description:

Code 12 means the ECM is "ON" and sees no reference pulse from the distributor Hall Effect Switch. This is a normal code with the ignition "ON" and engine not running. Code 12 is not stored, and will only flash when the fault is present. With the engine running, Code 12 would mean an open or ground in reference circuit from Hall Effect Switch to ECM, or faulty switch. Code 12 will set with a Code 41 if the reference signal is missing. If it is intermittent, only a 41 will store.


Test Description:

1. This step checks for a poor connection at the EST 4 wire connector as being the source of no distributor reference pulse. Check for corrosion, connector terminals not fully seated, or terminal not properly attached to the wire. The terminal must be removed from the connector and carefully inspected.

2. This step determines whether the fault is on the ECM side or the distributor side of the EST connector. With the engine running, the normal voltage of the Hall Switch will be about 1/2 battery voltage regardless of RPM.


2A. If voltage is between 4-9 volts, the problem is not in the distributor, but in the circuit to the ECM, or the ECM itself

2B. Over 9 volts could occur if the Hall Switch ground was lost, or if the switch was faulty.

2C. Under 4 volts could occur if there were no 12V ignition source, faulty circuit or connections from Hall Switch to EST connector, or a faulty switch.