- OFFICIAL GEARHEAD -
Join Date: Feb 2005
Location: Atlanta, GA
My Ride: CSX/CS/GLHS
Thanked 0 Times in 0 Posts
Re: 85 dodge 600 won't even idle now
The logic module (ECU) will not forget its programming if unplugged from the car or battery is disconnected. It will however forget any stored fault codes each time it is disconnected from power.
Fault code 12 is totally normal and expected every time you disconnect the power/battery. It will eventually go away after you start and run the car several times.
A 54 can actually be a number of things. When this one appears, it runs rough because the logic module will guess at injector timing. In my experience this code gets stored when there is a problem somewhere in the HEP circuit. A 'problem' can be a lot of different things so the code is really more of a point in the right direction rather than an actual 'here is the problem'.
First, the 84 and 85 distributor is different than an 86+, so is the HEP. So confirm that you have the right distributor, the right HEP and all the connections throughout the complete HEP circuit are good. I know this might sound silly, but I have worked on cars that ran poorly because during a repair one part or another was swapped during a service and it was the wrong part. Also TBI distributors are DIFFERENT than turbo distributors.
Many aftermarket HEPs are garbage by the way, and many of us have had them fail right out of the box or not far down the road. Sure there might be some exceptions but you'll never go wrong with a Chrysler HEP and it will last. The HEP shares a ground with the CTS and other sensors, so you have to check this circuit from end to end, of course it sure helps to have a wiring diagram. If you don't have a FSM, we can also provide you the wiring diagrams you need.
The logic module has a habit in cars that are not run often or parked for long periods of getting a little cold connection or two at the red/blue connectors. Its amazing how many cars get fixed by just removing the logic module, checking and cleaning the pins, then adding some dielectric grease to the red/blue connectors. The dielectric helps to prevent future corrosion as well as forming a moisture barrier that helps maintain the connection while parked or not being driven much.
Check those engine grounds! There is a big fat one at the drivers side front of the cylinder head. It leads into the front charge harness. Make sure it is connected to the head and the bolt is tight. Make sure the intake manifold to firewall ground strap is present and tight, that will make them go nuts for sure. There is also a supplemental grounding strap that goes over the passenger motor mount and one from the negative battery terminal over to the inner fender well, just behind the intake of the power module/behind the battery.
There is also a fuel injection harness ground, this two black wire ground is along the fuel rail, and is attached under the fuel rail mounting bolt typically. It's an important one but would not cause a code 54.
It is not possible to plug the HEP in incorrectly, the connectors are made different to prevent this.