no trigger signal to ign coil,no bus
#1
09-22-2014, 08:37 AM
Join Date: Jan 2010
Location: NJ
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no trigger signal to ign coil,no bus
Hi folks,
I have a 2002 Dodge Ram Van 1500 5.2L with 119k miles.
I've had a no start condition that has stumped me. I wasn't able to get a read with my scanner. The odometer blinked and showed "no bus". I wiggled the 3 connectors on the PCM to see if any relays would activate. None did. I then removed the 3 connectors and inspected them. They were all very clean. I sprayed them on both the pin sides and the socket sides with contact cleaner and let them dry for 20 minutes. I pulled off the PCM cover to see if the internals would show burn marks. Nothing looked obviously burned. I cleaned the ground contact areas of the PCM screws and firewall and reinstalled the PCM and tried to start the engine. Still a no start condition. I read something about the instrument cluster connector at the back of the cluster could be burned and would cause a problem. I removed the cluster. The connections appeared to be clean, solid, and not heated. This is weird, after I reinstalled the cluster I was temporally able to get the "no bus" to stop appearing on the odometer and the relays clicked. I then read about doing the key switch cycle 3 times to get a P code and the crankshaft position sensor code came up. I replaced it. It didn't help. I changed the camshaft position sensor too. Still didn't help the no start condition. The "no bus" came back at some point and remains. I have checked the fuses on the side of the IP. I checked the open top contact power fuses that are under the hood by the brake booster. They were good. I swapped the ASD relay with the next in position and nothing changed. Relays are still silent at this point. I opened the ASD fuse cap and tested that with a test light. It tested good with a test light. The other fuses all look clean and bright silvery through the top caps of each fuse. I didn't test it any its terminals though. I did a test to see if the coil was giving spark and it wasn't at both the distributer cap and the the coil tower using an HEI tester plug. I then did a test of the signal to primary side of the coil and I got a solid ground signal on the trigger side on the ground wire. It did not flash with a test light like it should. I don't recall what the positive side did. It was either on or off, not flashing with the test light. I have to get someone to help me again to do that test. So, there is a problem with the signal to the coil. I don't know where to go next.
Just to give a history of the van, about 12 months ago I did a tune up including: new wires, cap, rotor, plugs, and air filter. One of the plugs broke off leaving the threads in the head. That was fun getting that out. Most of the plugs were very hard to get out due to the rust and time that they in the engine. The water pump was leaking and I replaced the water pump and radiator shortly after the tune up. I've had the van
since it was new. I never had any no start condition like this. I don't want to randomly replace the PCM without being sure what is the root cause and taking a chance that I burn out the PCM. I don't like to guess on a fix without finding out the real cause.
Any and all responses would be appreciated. I will get back on any questions and findings. Thank you to all.
coil, no bus, ignition coil, no start, PCM,
I have a 2002 Dodge Ram Van 1500 5.2L with 119k miles.
I've had a no start condition that has stumped me. I wasn't able to get a read with my scanner. The odometer blinked and showed "no bus". I wiggled the 3 connectors on the PCM to see if any relays would activate. None did. I then removed the 3 connectors and inspected them. They were all very clean. I sprayed them on both the pin sides and the socket sides with contact cleaner and let them dry for 20 minutes. I pulled off the PCM cover to see if the internals would show burn marks. Nothing looked obviously burned. I cleaned the ground contact areas of the PCM screws and firewall and reinstalled the PCM and tried to start the engine. Still a no start condition. I read something about the instrument cluster connector at the back of the cluster could be burned and would cause a problem. I removed the cluster. The connections appeared to be clean, solid, and not heated. This is weird, after I reinstalled the cluster I was temporally able to get the "no bus" to stop appearing on the odometer and the relays clicked. I then read about doing the key switch cycle 3 times to get a P code and the crankshaft position sensor code came up. I replaced it. It didn't help. I changed the camshaft position sensor too. Still didn't help the no start condition. The "no bus" came back at some point and remains. I have checked the fuses on the side of the IP. I checked the open top contact power fuses that are under the hood by the brake booster. They were good. I swapped the ASD relay with the next in position and nothing changed. Relays are still silent at this point. I opened the ASD fuse cap and tested that with a test light. It tested good with a test light. The other fuses all look clean and bright silvery through the top caps of each fuse. I didn't test it any its terminals though. I did a test to see if the coil was giving spark and it wasn't at both the distributer cap and the the coil tower using an HEI tester plug. I then did a test of the signal to primary side of the coil and I got a solid ground signal on the trigger side on the ground wire. It did not flash with a test light like it should. I don't recall what the positive side did. It was either on or off, not flashing with the test light. I have to get someone to help me again to do that test. So, there is a problem with the signal to the coil. I don't know where to go next.
Just to give a history of the van, about 12 months ago I did a tune up including: new wires, cap, rotor, plugs, and air filter. One of the plugs broke off leaving the threads in the head. That was fun getting that out. Most of the plugs were very hard to get out due to the rust and time that they in the engine. The water pump was leaking and I replaced the water pump and radiator shortly after the tune up. I've had the van
since it was new. I never had any no start condition like this. I don't want to randomly replace the PCM without being sure what is the root cause and taking a chance that I burn out the PCM. I don't like to guess on a fix without finding out the real cause.
Any and all responses would be appreciated. I will get back on any questions and findings. Thank you to all.
coil, no bus, ignition coil, no start, PCM,
#3
09-24-2014, 12:00 PM
Join Date: Jan 2010
Location: NJ
Posts: 42
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I originally double spaced it and had more paragraphs. I clicked on something and it all changed. I got tired of correcting the spacing over and over. Sorry.
I just saw your reply after doing a search for any responses.
Do you recommend just changing the PCM without finding any causes? I am afraid of taking a chance of burning out the replacement PCM. I don't have the money to spend being I am on a fixed income.
Some conditions have changed.
I left the key on overnight when I started this thread, battery disconnected, and the instrument cluster out.
In the morning I touched the battery cable to the battery terminal and the relays started clicking. I left the battery cable off, turned off the ignition key, reinstalled the instrument cluster and turned the key on to crank it over. I connected the battery. The relays stopped clicking and it was a crank and no start condition.
Are there any businesses that test the PCM to see if they are not damaged?
Thanks
I just saw your reply after doing a search for any responses.
Do you recommend just changing the PCM without finding any causes? I am afraid of taking a chance of burning out the replacement PCM. I don't have the money to spend being I am on a fixed income.
Some conditions have changed.
I left the key on overnight when I started this thread, battery disconnected, and the instrument cluster out.
In the morning I touched the battery cable to the battery terminal and the relays started clicking. I left the battery cable off, turned off the ignition key, reinstalled the instrument cluster and turned the key on to crank it over. I connected the battery. The relays stopped clicking and it was a crank and no start condition.
Are there any businesses that test the PCM to see if they are not damaged?
Thanks