Chrysler Repair: 1995 concorde 3.5L no spark,no start, spark plug wires, leaking radiator

Question
Car was working fine when parked. The next day would turn over fine, would not start.  Pulled spark plug, no spark.  Pulled codes, only codes 12 and 77. Makes sense as battery was disconnected two weeks ago to replace radiator. Worked steps in Chilton manual, Coil pack checks out ok. Spark plug wires ok. With the ignition key on the Chilton manual states that there should be power on the green/orange wire at the coil pack.  There is positive voltage on Green/orange.  While cranking, using a LED type tester, there is trip signal ground on the white, red, but not the black wire.  All connectors look good. Chilton manual states that if no trip signal- computer (PCM) is defective. Replaced the PCM computer with junk yard swap with no correction to problem.  The replacement PCM is not same part # however they state at the yard that it is for same car, just different size tire. Maybe cause speedometer difference. There is not spark on any  cylinder which seems odd if there is what appears to be trip signal ground at the white and red wire of the coil pack.   The new computer, after attempting to start multiple times, only shows code 12.  Makes sense as battery was off PCM.   All plugs have fuel.  Only trouble prior to this no start issue was an overheat due to a leaking radiator  two weeks ago.  Radiator replaced, car has run fine after that.  Would like advice. Is it possible that the new PCM is not correct even though off 95 Concorde. Have not checked out wire 17, 18, 19 on PCM itself, as do not really know what to look for.  The Manual also shows connector C155 (coil pack) that is what I have made tests at.  There is shown also C141, however I do not know where this is physically located to check out that connection.  

Answer
Hi Glenn,
So the coil and its wirings prove out. That being the case if you still aren't getting the same pulsing pattern at the coil drivers of the three pins at the PCM one would have to suspect the PCM. I am not familiar with whether a compromised crank or cam sensor (or maybe a damaged slot pattern in the surface that they are sensing) could cause such an inconsistency between the outputs without setting a fault code, so that might still be an explanation. If the discrepent output pattern was the same whether you were using the original or the substitute PCM then I would lean toward the problem being with a sensor. To test for these possibilities, you can put a voltmeter across the signal output and ground wires of each sensor, turn the ignition key to the "run" position, and then crank the engine over by hand using a wrench on the crank pulley. As you do watch the voltmeter to pulse consistently from 5 to 0.3 volts as you go thru two complete revoloutions. If you miss a pulse in the otherwise consistent pattern would prove that a sensor or its interface was the problem.
Also you might want to make sure that the donor pcm came from a car with the 3.5L engine; the 3.3L was also used in those cars.
Roland





Hi Glenn,
I would check whether you have continuity in the three wires between the pins 17,18, and 19 of the 60-way plug at the PCM and the white, red, and black wires at the coil pack plug, C155. If the black wire seems to be o.k. and yet you don't get the ground pulse from it when measuring at the pin of the disconnected C155 while cranking but you do get the pulse on the red and the white then the PCM is probably bad because I would expect to either get a code 11 or a 54 if the crank or the cam sensors were bad. If you find that the black wire is o.k. and that you do see grounding pulses on all three wires at the disconnected plug, then I would test the resistances of the primary and the secondary windings of the coil pack. The resistance of the primary windings should be 0.45-0.65 ohms (measured  between the pin that connects to the dark green/orange wire and each of the other three pins of the coil, and then measure the resistances between each of the three pairs of towers (1 to 4, 2 to 5, 3 to 6) which should be 7,000 to 15,800 ohms. So see how those measurements work out.
Then write back to me with the results.
Roland