hey all, this problem has kept me perplexed for a while now. There's a bit of a story behind all this, so bear with me.

I have a '96 Dakota 2WD 2.5L, manual transmission

First, fuses started blowing when I'd press the brake or use the turn signals. I didn't have time to look for the issue, so i just kept putting in new fuses until i was pulling into my driveway and the engine just died right as I was parking it (lucky!) but hasn't ever started since. I plugged my OBD scanner in and there was no coms w/ the PCM. I listened for the fuel pump prime pulse as well. nothing. I went to a junkyard and got a PCM from a truck exactly like mine and now i have coms with my OBD scanner as well as the fuel pump prime pulse as soon as the key in at "ON" so i assume the PCM works now.

I pulled all rear lights and put them in one by one, turning lights using turn signals and all. I couldn't narrow the shorting circuit down. I eventually had them all back in their places with all lights on, brake mashed, turn signals on, hazards on, and nothing blowing a fuse. I don't know what was going on there, but whatever. That's not the pressing issue anymore. The engine is.

Now: I turn the key and it turns over, but there's obviously no combustion. Pulling spark plugs, there's no spark. Why? I check the power going into the coil with a multimeter. When the key is turned to on, there's power for like 2 seconds and then there's a click (the auto shutdown relay) and then no power to the coil. Why not? I did all troubleshooting in the FAQ to verify proper function of the ASD relay and it checks out. I even swapped it with the A/C relay and got no change, so I don't think it's the ASD relay. Next, I jumped the [switched] leads of the ASD relay with an alligator clip, checked the voltage at coil. There was voltage. Tried cranking, and still no spark.

So my first question: Is it normal for the ASD relay to switch off so quickly after the key is at "ON"?
--If yes, then should it switch back on once i start cranking?
--If no, then what would cause it to do that. is the PCM looking for some signal and shutting it off because the signal isn't there?

Is the PCM looking for a signal from the distributor? (could the distributor be bad?)
I hear the fuel pump, but I don't know what the fuel pressure is to verify that it's working. What's the best way to do that without removing an injector or squirting fuel everywhere? I get flashing error code 42 when manually pulling codes. It means that the fuel level sender unit voltage is out of range (makes sense, since my fuel gauge doesn't read correctly anymore) but would that be connected with this problem?)

Sorry for so many questions. Please answer any, or all of them. Any suggestions will help! I've never encountered an ASD relay on any other vehicle, so i have no idea how to proceed.

 

It sounds like with the lights/fuse problem you killed your PCM. There was probably a short on a power wire that shorted out and caused your problems.

When you turn the key it is normal for the ASD and fuel pump relay to turn on for 3 seconds or so to prime the lines for a fast start.

Are you sure your reading the codes correctly? Here is the link https://dodgeforum.com/forum/1st-gen...-96-codes.html

Code 42* Fuel pump relay control ckt, Auto shutdown relay control ckt, No ASD relay output voltage at PCM, Fuel level sending unit volts out of range, Fuel level unit No change over miles

You may be a victim of the notorious splices. They provide power for the relays. The FAQ has a great write up on it.

Or you got more shorting problems in the wiring.

 

thanks for the response, Crazy4x4RT.
I figured that the light/fuse problem killed the PCM, but after trying to narrow the short location with no success, I don't know if I'll just end up killing it again.

Ok, so it is typical for the ASD relay to turn on for a few seconds and then turn off again? Is it typical for it to come back on when cranking? Because it doesn't.

yes, I read the codes correctly. I'm assuming it just means the fuel sender is bad, which would explain why the gauge has been screwy recently. I just don't know if the PCM takes that into account when deciding whether to recharge the ASD or not, after the initial [aforementioned] prime. That's why i mentioned it.

I considered the splices, but before undoing all the wrapping, I figured the troubleshooting would have eliminated the possibility. Wouldn't the fact that the ASD relay turns on indicate that it is, in fact, getting the power through the splice? Wouldn't this therefore indicate that there isn't a splice problem? I'm assuming the splice you're referring to is the splice in the harness just below the fuse box. If I'm wrong about it, then I will check it first thing.

 

The splice could be bad causing you to have power at key on then because its a bad or corroded connection loose the power after a short period. If it were me I would start there since it is a common issue and eliminate that by doing the proper repair on it. If in fact the splice was not the problem then atleast it has been fixed and you dont have to worry about it causing problems in the near future. Plus you won't have the little voice in the back of your mind during the troubleshooting wondering if in fact that the splice could still be the problem. Also the short that you had that was blowing fuses for the lighting could have been the PCM since you replaced it and now you can't locate the short. Try getting a wiring diagram and check the wiring for that fuse for shorts to the frame. Another thought is the PCM that you pulled from the salvage truck could also be bad and causing the problems you now have. That could be the reason someone scrapped the truck (they couldn't find the problem causing there truck not to run) unless you know for a fact the truck was running when it was brought to the scrap yard.

 

No! Don't say that! I don't know how I'd troubleshoot that except have some donor truck handy where everything works and swap PCMs. Or else drop $200 on ebay for a PCM that's known to function. I don't know why the truck was scrapped. The body is completely whole.

I'll go ahead and do the splice fix and update you on whether that helped or not.

 

Just tore off the harness wrapping. It looks like the splice was already taken care of. [UPDATE:] I notice you guys telling me to check splices have pre-96 models. I think Dodge took care of this by '96 because i tore the harness apart on the truck in the junkyard and it looks identical to this. This is a factory job.


I'm going to buy some heatshrink tubing and tear into it to make sure the splice is still good. I'm assuming this is the one, since i can't tell from the FAQ what color the wires are supposed to be (they look more pink/orange than red)

If the splice is good, what else could be wrong besides the PCM? Please. I'm not very familiar with the electrical or ignition system on this truck, so I really need any help I can get.

 

UPDATE: I just found from the wrecking yard that the donor truck started and ran fine. It was only scrapped because the transmission was dead, so I have no reason to believe the PCM is dead.

 

I figured if i had power going to the coil but no spark coming out of the coil, then possibly something was wrong with the coil. I got a coil to compare it to and found no difference, so the coil isn't the problem.

If the hall sender in the distributor wasn't sending the PCM its signal, then the PCM wouldn't send a voltage pulse to the coil, so i wanted to check the distributor. with the distributor pulled out, i disconnected the coil output wire from the center post of the distributor cap and plugged a spark plug directly into it. Then with the key in the "ON" position, i spun the distributor by hand, hoping to confuse the PCM into thinking the engine was spinning, but I got no spark. I tried it with another distributor. same thing. I conclude it's probably not the distributor.

I know my mazda won't fire if the camshaft position sensor is disconnected, but I didn't see any mention in the Haynes manual of a camshaft position sensor. I'm off to the crankshaft position sensor now.

 

That looks like the factory cloth tape. Although it doesn't look corroded it is best to still open it up and take a look.


Yes you do have a crankshaft and a pickup coil (camshaft) sensors. If you don't have one plugged in or one is bad the engine will not start. Have you tried to read the engine codes?

 

the splice is good. I checked it yesterday.

yes, I checked the codes. I got error 42, which indicates the fuel level sender voltage is out of range. Last night I realized one of the wire harnesses (the one going to the fuel pump and stuff) had fallen into the wheel well and was chewed up pretty bad. There were several wires that were actually broken and others that had the insulation ripped off of them and were corroding. I spent the whole morning repairing them. I tried starting the truck again hoping that was the cure-all for my problems. It didn't start.

I pulled the codes: 12, 55
At least the 42 code went away now. The only thing I haven't messed around with is the crankshaft position sensor. To test whether it was good, i disconnected the crankshaft position sensor and tried starting. I expected a code (code 11) to come up, indicating there was no coms w/ the crankshaft sensor. I got no error.

recap:
-no spark.
-bought replacement coil from junk yard. went through all coil checks (resistances on primary and secondary coil) to find it's good. Even tested it manually. It's good
-bought replacement distributor (w/ built-in camshaft pos. sensor, as I found out later). I tried comparing the electrical properties of the two. They're identical.
-With a spark plug in the coil output (and grounded against the A/C compressor) I turned the key to on and spun the distributor w/ my hand and still got no spark out of the coil.
-I checked continuity between the coil connector and the PCM. Continuity checks out.
-I checked continuity between the distributor output (camshaft position sensor) harness and the PCM. it checks out.
-I checked continuity between the crankshaft position sensor connnector harness and the PCM. it checks out as well.
-I checked continuity between the ASD relay and the PCM (even though it has been clicking the whole time) and it checked out as well (although I already knew that)
-I checked continuity between the input and the three outputs of the splice under the PDC (fuse box). I even jiggled the wires while doing it. Continuity was constant. Had a friend check them again with his fancy lead tester tool. Same thing.
-Found shredded bunch of wires in left wheel well that tire had chewed up. Fixed them all. Code 42 went away. Still no spark.

what next?