QuestionQUESTION: Hi Roland,the wires on the oxygen sensors were ok,so were the wires going to the coil pack. My mechanic said there was a ground wire going to alternator that was loose so he tighten that up and did a tune up(new coil pack,spark plugs and wires.drove it around that night no problems, the next morning it cut off on my daughter,it started back up,took it back to the mechanic and he said it may lost oil pressure, the reason it cut off because oil was leaking from the filter.he put a new filter on,got it back drove it a couple of hours last night no problems, it cut off again this morning and blew the engine fuse. Is there something else going on. Thanks in advance for your help. Cornelius.
ANSWER: Here is the history of the problem:
Question:
hi Roland my 2000 town and country 3.3v6(flex fuel)blew the 20amp engine fuse 3-4 times a couple of weeks ago while driving down the street. I took it my mechanic, and he said it had following codes p1389 and p1282.he also that, that meant the pcm(computer)needed to be replaced. i bought one from o'reileys drove it with no problems for 30 minutes, then the next morning I took it to the dealer to be programed and about 15 minutes after leaving the dealer after I stopped and got some gas it started doing the same thing again, after the 4th or 5th time it would blow the fuse soon as I tried to crank it. can you help me out? do I need to get another pcm or is there something else I need to look for or do?
Answer:
Hi Cornelius,
Those fault code are merely saying that the automatic shutdown relay, which carries the output of fuse 17, is not putting out the voltage (which is obvious when the fuse blows).
That fuse does send current to the PCM but I don't think that is your issue. Rather it also provides 12V to the spark coil pack, the fuel injectors, and heated oxygen sensors. I would suspect that the harness connecting the plug of one of the oxygen sensors is broken and shorting the 12V to ground which then blows the fuse. The wires of those oxygen sensors are very thin and subject therefore to breaking apart and thus shorting to nearby metal or a ground wire. So set aside the PCM as the cause.
There are four oxygen sensors, 2 upstream mounted the exhaust manifold on each bank, and then downstream following the catalytic converter on each side. Inspect the four wires on each of the sensors to see if you can find one that is broken/shorted. If that isn't found, then check the resistance to ground of pin 2 of the coilpack (which has a brown/white wire that carries in the 12v from fuse 17 and similarly check a splice at the rear of the engine's cylinder heads where the same brown/white 12V wire connects to the wires for the injector banks. That splice has been know to overheat, melt its insulation and then short to ground as the result. The resistance reading to ground of any of the injector brown/white wires will be low ohms but not 0 if OK.
I hope this will solve the problem. If so it is too bad that you spent money for the pcm.
Roland
Follow up answer:
The "engine fuse" of which you speak is #17, correct? If not then tell me which one blew.
As I originally told you that is the one that provides current to the automatic shutdown relay which in turn powers the PCM, alternator field coils, the spark coil pack, the fuel injectors, the heated oxygen sensors: all via a dark green/orange wire. Somewhere along those many pathways of the group of wires there is a short to ground in the wire or short to ground in the object(s) being powered from such a wire. Go over the list with the mechanic to verify that all those pathways have been checked while flexing all the harnesses that have that color wire and looking at the heated oxygen sensor once again.
I question that he found a "loose ground wire that goes to the alternator" because the alternator is actually grounded directly to the engine block. One dark green/orange wire does indeed go the alternator so examine that wire as if it was shorting to ground that would blow fuse 17. Again, there are numerous locations for a short in a wire that comes from fuse 17 to occur and it just has to be found to solve the problem.
The fault code 1282 reports a problem with the fuel pump relay control circuit but that one is powered by fuse 16. So be sure that we are dealing with blowing fuse 17 rather than 16.
Roland
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QUESTION: Good morning, Roland, my mechanic never could find a wire that was shorting out, but let van run for a couple of hours to see if it would shut off, even let it run without the oxygen sensors and it still wouldn't shut off. I'll be taking it a shop that specializes in electrical repair to let them look and see what they can find this morning. I'll keep you posted. Thanks Cornelius.
ANSWER: If it can't be provoked into dying of blowing a fuse I wonder whether the shop can do anything, but give it a try. Please let me know what happens. Thanks
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QUESTION: Good afternoon Roland this a follow up to my problem with the blown engine fuse.
You was right, after I last emailed you I took my van to Goffs automotive electrical repair shop here in tarrant ala.it took them about a week but they found the problem 1 of the wiring harnesses that go down and around the engine and transmission had a short in it,they fixed it and haven't a problem since then. Thanks for your help you was right with your diagnosis. Now I have a new? I have a 96 town and country 3.8v6 that's been sitting a couple of years I'm trying to get started. I replaced the fuel pump I took off and put on the other van and have a hot battery but she want start. Lights come on ,but she won't spin over.do I need to check the starter or is there something else I should look. I originally stopped driving it because of transmission issues, other than that I didn't have a problem with it . trying to get it back on the road. Thanks Cornelius and happy thanksgiving.
AnswerHi Cornelius,
Thanks for the update and success report.
On the starter motor: Check fuse #5 (40 amp) in the power distribution box in the engine compartment, and check the fuse-like device #10 in the bottom row of the junction box under the dash. Then put the gear in start or neutral and have a helper try the start position of the key while you listen for a "click" to come from the starter motor relay which is in the power distribution box. If none, then try moving the gear shift slightly off the detent position on either side and try that again. If you get the click then the relay and safety interlock is working then the question is whether the current from the relay is getting to the starter motor solenoid (it should click loudly if so) and if not then check the brown wire which goes from the relay to the starter motor to see if it shows 12v when the relay clicks. If it does and you are getting a loud click from the starter solenoid switch, then carefully check the fat red wire from the battery to the starter motor (for safety disconnect the battery before using any tool on that wire).
Let me know if you can't find the problem.
Happy Thanksgiving as well to you.
Roland
PS: What the mechanic suggested, to lube inside the cylinders, would be correct IF the starter motor solenoid switch is clicking loudly but the engine won't rotate. If you are not getting that loud click, then what I suggested is correct.
