Okay heres the whole story... Van ran fine, then after shutting off one day, no spark. The engine light and generator light would just flash, and you could hear the ASD and injectors clicking over and over. Tried to hook a scanner up, but it wouldnt connect to the PCM.

Bought a rebuilt PCM, installed it, same problem. Replaced the Crankshaft position sensor and now the flashing check engine light is off and and the ASD just engages like it should when the key is on. Appears the Crankshaft sensor was shorting out and causing the flashing lights and clicking noises.

Now there is no spark, we checked it by taking the ignition coil wire (that goes to the distributor), sticking a screwdriver in it and holding the screwdriver about a half inch away from the block. There are no codes stored in the computer. Checked camshaft position sensor and its good according to the repair manual i bought at autozone.

After checking wiring diagrams and voltage i saw that the ignition coil was getting 12v, so i replaced it, still nothing. Then i realized that the other wire that goes to the coil is a signal (ground) wire coming from the pcm. I tested that wire for continuity to a ground while cranking and i got nothing.

Which lead me to believe there was something wrong with either the camshaft or crankshaft sensors, so i double checked them. Camshaft was good. Checked the crankshaft sensors wires. 1 is a 12volt supply, 1 is a ground and the other is a signal wire according to the wiring diagram. When i check the wires i get 12 volts on two of them and a ground on the other. When i plug it into the sensor, one of the wires drops to 5 volts, one remains constant 12v and the other is ground.

I have a feeling i have a short in the harness, since both of the wires are getting voltage. Has anyone else experienced something like this or can verify the readings for the wires going to the crankshaft sensor? Any help would be greatly appreciated. Ive been working on this thing for week and am at my wits end.

 

I have a simaler issue with a 1997 van 1500 5.2L im not getting any voltage at the camshaft pos sensor(suppost to be 8Volts at the supply wire) nor at the ignition coil. im starting to think that i have a bad ECU but i dont know how to test it.

in your case the wire that drops down to 5volts should be your signal (tan/yel) wire so as u turn over it should pulse between zero and 5volts. if u suspect a short check for continuity between the wires.
wish u luck.

 

All those wires have continuity. I called to company that sent me the computer n they sent another computer out. Now Im only getting .5 volts at the ignition coil. Anyone have any idea what causing this?

 

I have a '94 B350 van with a 5.9L engine. It has an intermittent problem. Since July, I've been driving the van while using an oscilloscope to monitor crank and cam sensors, 8V, and the ASD signal. I recently acquired a lot of useful data when the van died and the scope triggered.

When I reconfigured the wiring to monitor one of the injectors and the coil driver (instead of 8V and ASD because they looked okay), I again collected more useful data.

When the van dies and won't restart, it appears there's a much reduced coil drive signal out of the PCM. When the van is running okay, the crank and cam position signals have negative spikes which are in sync with drive pulses to the coil. In other words, the drive pulse to the coil could be corrupting the crank and cam pulsetrains via some problem with the PCM's power and/or signal returns or grounds. It could be a problem with the coil driver output stage. But it might also be an intermittent problem in the coil secondary.

The problem is either with the PCM or the coil. If it's the coil, it's probably an intermittent short in the coil's secondary winding. On the primary winding, I'm seeing 12V before the PCM grounds the low side. Even when the PCM stops grounding the primary (i.e., when the engine dies or won't restart), I still see 12 Volts at the coil drive pin on the PCM.

So, I'd really like to find a schematic of the PCM's internals to see if I can figure out if the PCM could be causing these peculiar waveforms. The owner of the van has spent over $1,200, over the past 4 years, to various repair garages (for this problem only) and he can't afford any more guesswork.

Thanks,

Jeff

 

Here are some pictures of my project to instrument the van. See this facebook link for pictures and descriptions of this project:

http://www.facebook.com/media/set/?s...45119cc&type=1

Jeff

 

I suppose that's one way to over-think and over-complicate the problem. Perhaps it's as simple as a spark plug wire with leaking insulation. The resulting EMF would be induced into the signal wires and mess with the internals of the PCM causing it to shutdown.

 

You reckon?

Several garages have tried. Problem was it wouldn't fail in their possession so they shotgunned it. $1,200 later, the church van still has the problem.

Hey, I won the scope in an online drawing and this is a small town with not much to do on Saturday nights! )

 

Look over the records that the owner has and see when the last time the plug wires were changed. If not changed with in this $1200 already spent and they look to be older wires then Alloro may have helped you solve the problem. Also do the plug wires have convolute covers on them? If not then the TSB regarding the spark plug wire routing needs to be applied to this van as well.

 

I remember viewing that TSB (spark cable rerouting) on my alldatadiy.com account. I'll keep that in mind. Thanks.

 

At the FB link, I added photos of earlier cases (Sept 3rd) where the engine started and shutdown with no appreciable spikes on CAM and CRK signls.

I believe the CRK and CAM spikes in the Sept 10th data are due to my mistake in signal routing: When I reconfigured to monitor the coil driver and injector #1 (instead of 8V and ASD as I had been doing), I didn't disconnect the 8V Return probe from the wire harness. Now, the coil driver signal is routed in the same 2-conductor cable with the 8V Return line.

As far as I know now, the spikes are only artifacts seen at the scope and are not affecting the CAM and CRK signals. I imagine the PCM has some filtering that takes care of the spikes. In other words, the van would die:
(1) before I connected anything at all to it;
(2) when I monitored CAM, CRK, 8V, & ASD;
(3) and now it's dying when I monitor CAM, CRK, COIL DRIVER, and INJECTOR #1 DRIVER.

I'll verify that disconnecting the 8V Return probe lowers the magnitude of the spikes on the CAM and CRK signals when the engine is running.