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1997 Dodge Ram 1500 Question: No spark and obd-2 not communicating

 

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missouriboy1, 5.9L V8, Phoenix, AZ, September 20, 2010, 00:00
 Rookie

I have checked all fuses that I know to check 3 times. ASD relay does not seem to click/engage when key is in run position, but starter relay will click/engage when key is turned to start. I have swapped known good relays but no results. I have also tested all sensors. Replaced coil due to case cracks, crankcase sensor due to intermittent connection while testing out of tranny case, and PCM. All sensors function for ignition when tested for hall-effect, but no power to coil when backpin tested with LED tester. 2 seperate code scanners have been utilized both before and after PCM replacement with no communication. Pin #16 and pin #4 on OBD2 connection plug have power and ground. The cig lighter even works. I even went as far as changing the the "engine light" bulb to ensure it worked properly, because it does not come on as if there is a problem. I even bought a new Bosch 700 amp battery first thing off to eliminate dead cell issues if they might have existed. Is there a secret fuse or something somewhere that I am missing and manual doesn't inform about? Helpful info would be greatly appreciated.

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  • Answer #1

    September 21, 2010, 15:07
     Master

    Sounds like you have a wiring problem. In a case like this, you will have to check continuity from the PCM connectors to all affected circuits including the OBD connector.. Also make sure each individual terminal in the connectors are in good condition and are a snug fit to it's mate and are not spread. Always back probe the terminal from the wire side with small pin to avoid damage to the terminals. Power to the coil side of the ASD relay is from fuse 9 (10amp) in the Fuse Block, and power to the switch side (powering up fuel and ignition systems) is fuse #4 (30amp) in the PDC.The PCM controls the ground to all relays in the Power Distribution Center (PDC). The circuitry in the PDC could also have failed in which case would have to be replaced.

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    missouriboy1, September 22, 2010, 23:18
     Rookie

    Thanks Johnny for the advice. I was also wondering if there is a good site to get the PCM pinout specs for my old Ram? I ran into several various readings on my ohm meter while testing earlier this evening and would like to know what the exact specs should be concerning sensor grounding loops. The manual I have is spread over too many years to incorporate all diagrams and specs within it for the PCM and OBD-2 connector.

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