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Automotive ecu

Thread starter #1
Greetings everyone ,im new here and in automotive industry ,usually dealing with ecus,has anyone tested ecus or know abt them,what i would like to know is if there is no communication with ecu ,how would one start checking ,does the processor work with 5 volts ,kind regards
I wish I could help and I wish there was more info out there. We have a 2007 Chrysler Pacifica with a BCM ... ECU starting issue. The computer effectively locks up or glitches sometimes when you turn the key to start the engine or once the engine starts, you can't shift any gears. I would love to fine out more information so that I could "fix" this issue.

dr pepper

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Most Helpful Member
If you crank the engine does the rev counter move, if it does then the chances are the Ecu and 5v rail are present.
Have you checked for spark & injector pulse, if you get either the Ecu is operating.
A no comms could be something on the comms network shunting the bus & stopping all comms, if this happens usually the airbag & abs warnings are on too.
Failing that the comms adaptor you are using may not be compatible with the vehicle, there are a few different protocols, some of the older ones may not be compatible with newer scanners or software.

Beu, does your issue stop the car from starting, or is it purely a gear shift issue, I'm in the Uk so chrysler isnt really my scene, however I'm aware they can have issues with the Tcm, its up front in all the weather.
"Beu, does your issue stop the car from starting, or is it purely a gear shift issue" ... Actually there are two issues but I feel that both are related to the flakeness of the ECU.
1) The starting issue acts like a dead battery when you turn the key but that isn't the case here. When you turn the key you hear one "click" and then you have to wait about two seconds and it starts right up. When this happens, everything else checks out just fine.... battery voltage, interior lights, headlights, etc... no noticeable dimming.

2) The gear shift issue doesn't make itself known until you drive down the road a little bit and realize that the gears are not shifting. The solution here is to pull over, turn the car off and try again and that usually fixes the problem. This issue doesn't happen very often.

dr pepper

Well-Known Member
Most Helpful Member
A lot of mechanics would be thinking starter, I'd be looking for exactly what is causing the click, if its the shudown relay then you can rule out the security system & look more closely at the starter, 'flashing' 12v to the trigger terminal would tell you if its sluggish or not.
As for gears shifting you'd have to look into the Tcm for that, you might be able to do that with a cheap Elm 327, have a look at some chrysler forums.
I think some chryslers if you do things with the ignition switch & pedals they'll show you fault codes on the Mfd.


Well-Known Member
I'd be checking grounds. If the car has been sitting for a few days when this happens, and the first try "heats up" the ground connection then the second try it conducts. And the shifting sounds like corrosion or loose connector in the terminals to the transmission.

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