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Are these signs of a bad ECM?

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Old 12-07-2010, 09:28 PM
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Question Are these signs of a bad ECM?

I have a friend that has a '99 2500 that wouldn't start after putting fuel in it. Long story short we figured out the lift pump wasn't working so I replaced it and found out the new one wasn't getting any power to it. I did search and found that a bad ecm causes this,is that correct? Im not real familiar with the 24 valves so any help is appreciated.
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Old 12-07-2010, 10:26 PM
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The pump only gets power for about 1 second when you turn the key to ON, and then runs continuously AFTER the engine starts and is running.

Try this, bump the starter as if trying to start the engine, but don't actually start the engine. Just give the starter a quick tap, and then return the key to the ON position. The ECM sees this as a failed start, and then runs the lift pump for 25 seconds to try and move fuel to the injector pump. You can then either check for power to the lift pump or hear it run if it's good. This is also a good trick after you change fuel filters to help purge the air from the filter and fuel lines.

Hope this helps.
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Old 12-08-2010, 02:40 PM
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I tried bumping the starter and got nothing. I checked the connection with a test lamp and I have no power going to it.
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Old 12-08-2010, 03:03 PM
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Before calling the ECM dead, check the fuses in the Power Distribution Center (PDC) on the drivers side of the engine compartment. I think it's fuse number 9 that protects the fuel system. Check for blown fuses there. Rule out the simple little things before replacing the ECM.
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Old 12-08-2010, 04:24 PM
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if truck runs good otherwise id just wireup a 12v relay and switch a new ecm is going to cost $$$
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Old 12-08-2010, 06:24 PM
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Unplug both batterys for at least an hour. This is said to sometimes 'reset' the ECM. My CaTCHER (Bombed ECM) is faulty and this helps mine.
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Old 12-11-2010, 05:19 PM
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Update. I wired the pump to 12 volt. My buddy tried either to get it going( bad move I know) and I noticed that none of the gauges read anything like the motor isnt turning. Is there a crank sensor to tell the ip when to turn on?
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Old 12-11-2010, 11:24 PM
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Originally Posted by d22019 View Post
Update. I wired the pump to 12 volt. My buddy tried either to get it going( bad move I know) and I noticed that none of the gauges read anything like the motor isnt turning. Is there a crank sensor to tell the ip when to turn on?
Cam sensor I believe actually. If it failed the ecm would not know that the engine was turning over. If you have no guages at all working I would be suspect of a major failure like the ecu, but I can't quantify that with prior experience of such happening....
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Old 12-12-2010, 09:05 AM
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Old 12-12-2010, 02:20 PM
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If that sensor goes out, typically you lose the tach, A/C, and alternator output.

It should still start though.

If none of the guages work, i also suspect a dead computer, unless one of them is unplugged. The PCM (Dodge computer) usually handles the guages and truck functions, while the ECM (Cummins computer) runs the engine.

At a bare minimum, the fuel and volt guage should indacate something with key on.

Have you checked the computer connections? Also check ALL fuses in both the Power Distibution Center (PDC) in the engine compartment, and the fuse box in the cab. This could be as simple as one (or both) computers not getting power.

Have you pulled any codes yet?
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Old 12-12-2010, 05:27 PM
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Im going to try pulling codes tomorrow. When the key is on the volts and the fuel gauge move but when its cranking the tach and oil pressure don't move. I did swap the relays around and I still have nothing.
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Old 12-12-2010, 06:50 PM
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Good, that indicates that your PCM is working. Have you checked fuse #9 and 10 in the PDC?
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Old 12-19-2010, 06:22 PM
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Another update: I replaced the crank sensor, both batteries and I still have no tach,no oil psi(on the gauge that is),and no start. I did hook up a scanner to it and had a 1689 code and that's been there for a year. All the fuses are good and connections to the pcm. The owner did mention something about the factory security system light doesnt blink anymore but I don't know if that's related.
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Old 12-20-2010, 09:51 AM
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Tach and oil pressure both feed into the ECM. 12v power to lift pump comes from ECM. Last thing you can check is pull the plug to a sensor and test for power. most sensors that are powered are fed either 5 or 12 volts.

This sounds more and more like the ECM is indeed bad.

As a new twist to things I looked up the trouble code that you got:

P1689 - No Communication Between ECM & Injection Pump Module
http://www.troublecodes.net/chrysler/99-01trk.shtml

Might want to check the wiring to the injection pump too.
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Old 12-20-2010, 03:07 PM
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Well I tried to hook up my scanner to it again and it says that it cant communicate with the ECM. What now, im really stumped.
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