It means, "I'm in diagnostic mode", "The Codes that follow are error
codes". 12, 12, 12, short pause, 12, 12, 12, long pause. Means "I'm in
diagnostic mode", "There are no error codes", "I'm still in diagnostic
Error code 12 means "no ignition reference pulses received by the
Since the conditions are that the engine is not running, there
will not be any ignition reference pulses.
There are a number of diagnostic modes available depending on the
resistive value placed between pins A and B of the ALDL.
When you short the ALDL with a jumper, you are in the zero K ohms
mode, using different resistor values such as 3.9K ohms or 10K
ohms or open will allow different diagnostic modes to be
activated by the ECM
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.