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Could use some help. Working on a 2008 Dodge Ram 2500 6.7 4x4 automatic , third time truck has come back for p2121. First time batterys where bad and terminals serverley corroded , replaced both batterys with new and new ground cable to block, test drove for and hour no problems sent truck out and it came back . Second time replaced throttle pedal with new test drove truck for an hour no problems sent truck out. Truck is back again, this time it after clearing code p2121 it comes back within 5 to 10 minutes. When looking at scan data app1 volts vs app2 volts I can see some small changes in app2 while app1 volts do not change. So I go ahead and connect scope . Back probe at throttle pedal , pin 6, 5 and 4. app signal , 5 volt and signal return. I routinley see a 300 mv spike on signal return which I see on 5 volt ref and signal so I back probe ground, connector 2 pin 57 at computer and see same 300mv spike on ground there too. Connect jumper wire from computer ground wire on side of block to battery negitive and no change what so ever. Not sure if I am chasing the wrong thing but this 300mv glitch is the only thing I see wrong. The 5 volt circuit is looks great , the signal looks great , but when the 300 mv glitch occurs occurs on the ground I see it also on the signal and 5 volt. Could really use some help and more direction to help solve this one.
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