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-   -   ECM Problems??? (http://www.ramforumz.com/showthread.php?t=61057)

dad22153 09-08-2010 09:26 AM

ECM Problems???
 
I have a '99 Ram 1500, 5.2, and can't get it started. When I turn the ignition on, I should hear the ASD relay click, but it doesn't. I located the power pin for the ECM, and when I test it for power, the relay clicks as it should. It sounds like the ECM may be bad, but before I lay out $200 for a new unit, I wanted to get some opinions, or suggestions on what else I should test for. Any help would be appreciated. Thanks.
Dave

deanthecrabman 09-09-2010 01:35 AM

Bump^^^^^^

dad22153 09-09-2010 09:28 AM

I could really use some help on this one....Thanks.

Dave

erm 09-09-2010 09:33 AM

I'm sorry...I have no idea what may be wrong. Good Luck!

JoeDodge 09-09-2010 10:08 AM

If the 5 volts which supplies voltage to the tps, map or crank/cam sensors gets shorted to ground, you will have this condition. If the cel/mil does not come on at key on, this may be an indicator that this wire is shorted to ground. But first, turn key to the run position and wiggle the wiring harness near the rear of the LH valve cover and the intake manifold. If you hear the ASD click, the 5 volt wire is shorted in this area. I have seen several wiring harnesses rub a hole in the wiring at the sharp edge of the valve cover. If this fails, unplug the map, tps and both crank/cam sensors with key OFF. Then turn key on and see if the ASD relay clicks on for 2-3 seconds and then goes off. If the ASD click, you have a shorted sensor or wiring to sensor. Key off, reconnect each sensor one at a time till you find which sensor is shorted. I think (not sure on this truck) there is a 5 volt supply going to the automatic trans. If this wire shorts to ground, it will shut the PCM down also...........or you could have a bad PCM..........JoeDodge

dad22153 09-09-2010 12:25 PM

Quote:

Originally Posted by JoeDodge (Post 305111)
If the 5 volts which supplies voltage to the tps, map or crank/cam sensors gets shorted to ground, you will have this condition. If the cel/mil does not come on at key on, this may be an indicator that this wire is shorted to ground. But first, turn key to the run position and wiggle the wiring harness near the rear of the LH valve cover and the intake manifold. If you hear the ASD click, the 5 volt wire is shorted in this area. I have seen several wiring harnesses rub a hole in the wiring at the sharp edge of the valve cover. If this fails, unplug the map, tps and both crank/cam sensors with key OFF. Then turn key on and see if the ASD relay clicks on for 2-3 seconds and then goes off. If the ASD click, you have a shorted sensor or wiring to sensor. Key off, reconnect each sensor one at a time till you find which sensor is shorted. I think (not sure on this truck) there is a 5 volt supply going to the automatic trans. If this wire shorts to ground, it will shut the PCM down also...........or you could have a bad PCM..........JoeDodge

Thanks for the suggestion....I'll check it out
Dave

dad22153 09-11-2010 09:28 PM

Well,
I was going to hit the junk yard yesterday to grab an ECM, but I figured I'd give the old one another try. Plugged in the leads, and I could hear the ASD relay click. Hit the key and the damn thing started up!

However......
I went to try and start it this morning, and NOTHING! This is becoming very frustrating. I'm still tempted to switch out the ECM, as I checked the wiring and could not find any shorts or broken wires.

Any other suggestions would be welcome. Thanks.

Dave

dad22153 09-29-2010 11:18 PM

Well,
I replaced the Crank Position Sensor and TPS sensor, and still no fire. Next on my list is to replace the Cam Position Sensor...hopefully that will help. I also sent out the ECM for testing and repair if needed.

One thing I did find...I had a gas leak from the fuel pump feed line. When I dropped the tank, I did find that one of the supply wires had almost broken off, and was only holding on by a strand or two. I replaced the damaged wire and hose connection today. I'm wondering if that frayed wire might have contributed to the problem. I verified the power source was good by grounding the power supply pin on the ECM plug, and turned on the igintion. The pump seems to work fine. With so many possible things that can go wrong, I don't know if this will help fix the problem. God, I HATE electrical troubleshooting!

Dave

JoeDodge 09-30-2010 10:08 PM

Does the "check engine" light light up and the fuel pump run at key on for a few seconds? If these items are not happening, replacing the cam sensor will do no good, UNLESS, you unplug the cam sensor, turn key on and check engine/fuel pump works. There is also a possibility that there is a short in a 5 volt wire at the transmission. This would shut the PCM down, no check engine light/no codes...nothing from PCM. There may be a "No bus" in the odometer display if the key is in the run position. JoeDodge

dad22153 09-30-2010 10:47 PM

Quote:

Originally Posted by JoeDodge (Post 323299)
Does the "check engine" light light up and the fuel pump run at key on for a few seconds? If these items are not happening, replacing the cam sensor will do no good, UNLESS, you unplug the cam sensor, turn key on and check engine/fuel pump works. There is also a possibility that there is a short in a 5 volt wire at the transmission. This would shut the PCM down, no check engine light/no codes...nothing from PCM. There may be a "No bus" in the odometer display if the key is in the run position. JoeDodge

No check engine light that I recall. Now I don't have the ECM, as I sent it out for testing. What I did do, was find the fuel pump power pin on the ECM plug, ground it and heard the relay click. I turned the key on, and the fuel pump went on.
In terms of the transmission wire, where specifically is this located? I'll check it out. I'm going to replace the cam position sensor in any case, as I was planning to do a major tuneup before cold weather hits. With respect to the "No Buss" on the dash, I am getting that. It's happened before, and did not affect the engine running. What typically causes the "no buss" condition? I heard that this is a typical problem with these trucks.

Dave


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