QuestionQUESTION: hi i was hoping you could help me i have a 99(T) chrysler grand voyager 3.3 and it wont start because the 20A engine fuse keeps blowing i have had somone out to look at it and they are saying its the green/orange wire at the coil pack thats causing this to happen and that the wire bridges of in 3 ways under the fuse box in the engine bay so do you know where these wire are going or what there for thanks ROB
ANSWER: Hi Robert,
If you mean the 20 amp fuse that is in the box under the hood, next to the last one in the rear and perhaps labelled "engine", then indeed that is the fuse that powers a lot of things via the autmatic shutdown relay. Unfortunately it does power a lot of things beside the coil pack: fuel injectors, alternator field coil, the heater coils of the oxygen sensors on the exhaust system, and also a wire to the pcm itself. I suspect the wires at the oxygen sensor first, as those are the most fragile to being shorted out, so take a look at both the sensor on the exhaust manifold and the one just beyond the catalytic converter. You could also disconnect their plugs, and also try the plug at the alternator and see if the fuse still blows, or measure the resistance to ground from the middle pin of the ASD relay socket which is where you will be able to notice a change from 0 ohms to some low (but non-zero) ohms when you have removed the shorting cause. If it persists, disconnect the coil pack and the plug to the fuel injectors.
I believe you will find the short.
Roland
PS Please 'rate' my answer and where you see the question of 'volunteer of the month' consider giving a 'yes' answer.
---------- FOLLOW-UP ----------
QUESTION: hi roland its robert again thanks for all the help you have given me. we have been tring everything you have said and we think the problem is in the pcm as we are getting a feed through the conectors apart from the blue wire on the ignition coil i was just wodering if you know if i can change the pcm with another with the same part number but the module number is a bit different
ANSWER: Hi Robert,
I wonder whether the pcm would blow that fuse. I don't believe it draws any power from the fuse. The wire that goes to it on pin 6 of the pcm is mainly to 'detect' whether the relay is closed or open for self-diagnostic purposes. If it shows a short to ground it is probably the wire, not the pcm itself.
So I would encourage you to do the resistance testing I described before trying a new pcm which would be to 'throw a part' at the problem in hopes that it would work. I don't know about the issue of the part vs. the module number. Tell me what you have found via resistance testing of the various components and maybe I can suggest some more.
Roland
PS Please 'rate' my answr, and where you see the question about 'volunteer of the month' please give me a 'yes' vote if you believe I deserve that. Thanks
---------- FOLLOW-UP ----------
QUESTION: hi the we only done a continuity test on the wires and they all seemed fine apart from the blue wire going on the coil pack we found all the other wires from the pcm came stright through from input to output apart from the blue had no signal at all im getting confused and i have called quite a few garages and they dont want to helf even my local chrysler garage said they couldnt do it thank again
rob
AnswerHi Robert,
I am not clear about a 'blue' wire on the coil pack. Do you mean the dark blue/tan wire on pin 4 of the plug at the coil pack? That one should show continuity to pin 3 of the pcm plug, and it should not show a short circuit to ground (any metal surface on the engine would be a 'ground').
Basically, check that the dark green/orange wire is not shorted to ground (with the asd removed from the socket, the resistance should read at least 1 ohm). And then check that the other 3 wires at the coin pack are not grounded with the plug at the pcm removed, similarly. If none of the 4 wires are shorted to ground, then we still haven't found what is the cause of the fuse blowing.
Roland
Please 'rate' my answer and consider the nomination question. Thanks
