Correction on the subject line, my bad it is P0203 not P0230...

Hi all. Hoping someone can shed some light on this issue for me. My 99 Grand Caravan has been a fantastic van throughout it's use. However after as usual running and performing perfectly just a few days before, it was parked a few days. I went to go into town with it and noticed a miss, and a lot of smoking (not Oil). I popped the hood and found a critter had built a nest on the intake manifold of the 3.8 MPI engine. Looked to be a bird nest, but on removing it, I found the wires badly damaged to the #3 fuel injector, so no guessing rodent.
anyway I do have a scanner, so I read codes and received P0203, P0300, P0301, and P0303.
Not having the manual I searched on line for what these codes were, 300, 301, 303 clear enough. "Misfire detected on multiple cylinders", "misfire detected on cyl #1"," misfire detected on cyl #3".
And the P0203 is listed as Fuel Injector #3 control circuit fault (open or Shorted), so that also made sense as the #3 injector wiring was damaged. I repaired the wiring, verified polarization to the injector, measured continuity to the injector plug, and as well measured resistance on the #3 injector to find 13 ohms (with in 0.3 ohms of the #5 injector). But on Clearing codes and restarting vehicle, I still have the miss, and almost right away get the check engine light. On reading codes again I get P0203, and if I rev a few times while running I will also get P0300, P0301, P0303, and eventually P0305 as well. I can understand misfire on cyl #3 of course if indeed a fault on injector #3, but misfire on #1 and #5 also? Interestingly all on the odd bank, no misfires on the even bank. Dvm measurement on the #3 injector also does show it is getting voltage pulses from the computer...

Anyone have any clues as to where/what I should be looking at here?

Thanks in Advance!
Doc.

 

My clue is you may have more damaged wires. Also you can have continuity on a wire but no current flow say if it's only one strand of wire making contact. You stated 13 Ohms but that's really high. Of course if resistance is abnomally high that could give an open cirucut fault

 

Thanks, I am suspecting I have a damaged driver in the PCM from the initial short condition that existed when I first found the chewed wires. As for the 13 ohms, yes abnormally high would indeed trip and "open" condition. However the remaining 2 injectors on the odd bank are showing readings of 12.7 & 12.8, which should yeild a difference in current of less than 20ma. with a normalized current of 1.09 Amps. I have inspected the remaining wiring, also did continuity and cross short checks and found nothing abnormal. I did also switch to ignition on engine not running, and with injectors #1, 3, & 5 unplugged and took voltage measurement at the plugs, that gave me another clue to the computer. Though obviously with out engine running or cranking there would be no signal present, ambient voltage should be the same as the circuits are identical. #1 & #5 showed an ambient of + 97mv, where as #3 showed an ambient of - 5mv. A 1/10th volt difference is certainly a very small difference in a 13.8V system, but a definite discrepency considering the driver outputs are supposed to be identical. But located a wrecked 99 in a local salvage and will be grabbing the PCM and the injector harness from it, and of course keeping fingers crossed...

 

Ok, Now I am even more confused. Injector wiring repaired, new PCM installed....

Exact same miss symptom still present. However PCM codes P0203, P0300, P0301, P0303 and the occasional P0305 are gone! Haven't come back in testing at all, however a new code is now showing... P0353 ok Coil primary/secondary circuit fault. Makes sense, and in fact is is not firing at all on Cylinders #3 or #6. Ok that is coil #3. DVM tests show 0.6 to 0.7 Kohms, and secondary (tower to tower) shows 12.6 Kohms, both primary & secondary are in spec. continuity tests, and short test show #3 coil driver circuit through and not shorted from PCM to coil. But with engine running, removing either #3 plug wire, or #6 plug wire have absolutely no effect at all on the engine. Yeah sounds again like PCM, only this is the new PCM, and exactly the same miss condition as the original.. WTF??

 

i seen that allot due to broken flex plate

 

Circumventor, Flex plate as in Engine to Torque Converter? So the logic there would be CPS is not picking up a signal for Cyl # 3, also would this not generate another trouble code related to the CPS?

 

thats the only part i know of called a flexplate. i had allot of them come thru and they aint never set no sync code. most didn't have good spark on the back cylinders. it acted like she was retarded on timing so i found tdc on #1 marked the crank pully and timing cover. started it up used an adj timing light and found the darn thing was 20deg retarded. dang thats the flywheel cuz the senser comes of that flex plate so out come the trans and sure nuf she was broke in the middle. now after doing a couple doz i got her figgured out allot faster

 

Man that totally bites... Guess I need to check it, would be nice to have scope for it, could tell if pulse missing then. #3/6 pair not firing at all, not just out of sync, absolutely no fire what so ever, just as would be expected from bad coil or harness to coil, or even dead driver on PCM. That was why I would tend to excuse the flexplate as not the problem, (I always referred to it as drive plate which is why I asked).

On the Grand Caravan, you drop the trans, or lift the engine? I am used to rear drive stuff LOL...

 

Before I would condem any component, you need a quality scanner with data stream capabilities and a quality diagnostic proceedure book such as Chrysler's Powertrain book for this year/make vehicle. I like the timing light idea, I confirm them bad using a dual trace scope looking at cam and crank signals at the same time. If the plate is cracked it will show being out of phase. I too have had no spark on some cylinders when this occurs. And if you can truely determine that is indeed your problem, I find pulling the trans is about 5 hrs faster than pulling the motor