Originally Posted by gagestruck
Could it be the Single Board Engine Controller (SBEC) ?
I am going by my 98 Dakota Haynes manual which has the same ignition
coil/cam sensor but sequential port FI.
The ASD relay is controlled by the ECM (or whatever the engine management computer is called on your truck (SBEC).
If the SBEC detects that a critical sensor input is missing or out of range,
it will operate the ASD relay to prevent possible harm to the engine.
These sensors include the cam sensor (distributor),
and the crank sensor (usually located behind the right (passenger side) cylinder block,
which generates pulses to the ECM when it detects a magnetic " timing tooth" on the flywheel.
These are usually a "Hall effect" solid state sensor.
(Read "Dodge Dakota has lost it's spark") here:
I expect there is one of these in your vehicle as well to determine
cylinder TDC (firing) position in relation to the flywheel gear teeth.
Unfortunately due to their nature, you cannot test these sensors
in a static mode with a DVM (voltmeter), in order to see what
the sensor is doing when the engine is cranking you need to look
at it with an ocilloscope. Here is a youtube video on how to
test these dynamically.
The Auto Shutdown Relay (ASD)
On mine, 12v to the ignition coil is control by a set of contacts on the
ASD. The low side (gnd side) of the coil IS controlled (pulsed) by
the ECM from the signals it gets from the Crank and Cam sensors.
I expect yours is similar.
On my sequential port FI V8, a different set of contacts on the ASD
cut the 12v to one side of the fuel injectors (pulse coil) and the
gnd side is controlled individually by the ECM.
The Fuel pump relay is controlled by the ECM, and I expect that
if the ECM doesn't get the inputs from the sensors it is expecting,
it shuts that down as well.
So in essence, when that happens:
1. You have NO spark
2. You have no Fuel injector pulsing, even with the 2 that should be there
on your throttle body FI)
3. You have no fuel delivery
You need to bypass the ASD relay, and perhaps the fuel pump relay
with jumpers to continue troubleshooting but this can be done
in two separate trouble shooting stages.
1. verify the ignition circuit on the ECM (coil driver) is working
2. verify that the fuel injector pulsing circuit on the ECM is working
If not, as in your case.
At this point, you need to see what is happening coming INTO the ECM
in regards to the 2 sensors (cam/crank), to see why the ASD
is BEING OPERATED by the SBEC.
It could be the SBEC, but first before changing that expensive control
board, you need to be SURE that all the required sensors are functioning within the parameters that the ECM/SBEC is expecting.
If the sensors are not functioning completely,you should get some kind of
check engine light code.
P0340 = no camshaft signal detected during engine cranking
P0320 = no crank reference signal detected during engine cranking
p1391 = intermittent loss of signal from either crank or cam sensor
If you are sure that the sensors are ok, AND the ASD is still being operated by the ECM,
then it is possibly something that has gone wrong inside the ECM.
OR some kind of input that is not there that is expected.
Whether it can be reprogrammed in that specific case, I don't know..but usually if there
is an internal fault in the ECM controller, you should get some kind of code (but not always, unfortunately :-)
P0601 = internal controller fault detected