Possible BCM issue??

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Jennylyn36

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I had to replace the starter, after replacing I try to start & it won't. The only way I can get it to start is by taking out a spark plug & pressing down on starter relay. Any ideas of why it wont start normally??
Thank you, it is a 2007 3.7 4 wheel drive
 

Jennylyn36

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Yes, it will start and run if I start by pressing down on the relay
 

Billwill

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Check all the fuses are OK...the relay coil will pick up its energizing voltage through a fuse somewhere.

Swap over the Starter Relay with an identical relay nearby.

Try start it in Park and in Neutral...one of these interlocks may be faulty.

After you start the Jeep by pressing down on the Starter Relay does the Jeep run OK with no CEL or Red lights?o_O

I presume that you have not removed a spark plug from the engine...that makes no sense!:eek:

The Actuator Pin Assembly could be failing...a common problem.

When you turn the ignition key to "Ignition ON" all the cluster lights will come ON. If you now turn the ignition key to "Start" you should feel some spring resistance on the key if the Actuator Pin Assembly has not completely broken but even if there is some resistance you will need to do the following:

Remove the plastic covers over the Steering Column....use a Male Torx Driver to remove 2 Torx screws.

The Actuator Pin Assembly and ignition switch is held onto the steering column by a smaller Female Torx screw.
Newer KJs have this small Torx screw as a "Security Screw" that needs a Male Driver with a hole drilled down its center.

Remove this screw and see if any debris falls down..a sure sign that the end of the Assembly is breaking off!

With the Jeep in Park or Neutral and the ignition key in its normal slot so as to energize the SKEES anti theft...use a small flat screwdriver to turn the Ignition Switch...engine should start and run.

If you need a new Actuator Pin Assembly get one from Dorman....the Dealers do not stock it.;)

There is nothing wrong with your BCM or PCM I believe...if not a broken Actuator Pin Assembly you may have a wiring break in the PDC (Power Distribution Center) which is the box under the hood with the fuses and relays....whereby the Starter Relay is not getting its voltage on its coil from the Ignition Switch.
 

Jennylyn36

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I have tried swapping relays out, and to start it yes I take a plug out, press down on relay & it starts right up, I then put the plug back in and it will run fine. I will try your other suggestions, thank you so much because I am completely baffled.
 

jp7794

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Hi Jennylyn and welcome. Spark plug eh? That is a head scratcher. Does it matter which one? Billwill is kind of the electrical guru here. KJs (Liberty) have been known to have electrical gremlins, but this is weird even for that. As stated above, it could be the actuator pin or maybe the ignition switch. However, those two things have nothing related to the spark plug. Please keep us advised in case others experience the same.
 

Billwill

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OK Jennylyn let's sort out this spark plug issue mystery!;)

With all plugs in place if you turn the ignition key to Start does the engine turn nicely over or does it struggle to move?

If you remove any plug does the engine now turn over faster and start? If so it would seem that there is not enough power in the Starter Motor to overcome the resistance you get from the engine when it is compressing on all cylinders.

If this is the case you should first get your Battery Load Tested to see if it is capable of supplying enough current to turn the engine over.;)

If the battery tests good or you get a new battery and you still have the problem then either the Starter Motor is bad or there is a voltage drop on the starter motor or a voltage drop on the electronic modules.

So with a good fully charged battery in place, check that both the battery connector leads are clean and tight. Make sure that where the negative lead goes to chassis that the connection is clean and tight.

There are two straps at the rear of the cylinder heads which ground the engine to chassis...make sure these two grounding straps are clean and tight both ends.

You need to get a Multimeter if you do not already have one...a cheap digital multi meter will do...I never travel without one in my Jeep!:)

Turn the meter to DC Volts and with the ignition OFF place the meter leads across the battery positive and negative leads.

The voltage should be about 12.5 volts or higher.

With the meter leads still in place...as you turn ignition to Start and the engine starts turning over...the voltage should not drop much below about 10 volts.

When the engine is running...no matter how you got it to run...the voltage on the battery should be around 13.4 volts.

If the voltage while turning the engine over is below 10 volts then the Electronic Modules such as the BCM, PCM and TCM may not operate properly so it will not fire!:(

If you have a good battery fitted...try get a thick cable such as the two thick cables on a Jumper Lead Set.

Take say the Black cable of the Jumper Lead Set and clamp one end on the Negative Battery terminal.

Clamp the other end of this Black Jumper lead onto the metal body of the Starter Motor...this ensures that the grounding from the battery to the chassis/engine will now definitely be good.

If engine now turns over nicely and fires up then your existing Grounds are bad ie. the Negative Battery lead going to chassis is not making good contact or the two grounding straps at the rear of motor are not making good contact.;)

Or your new Starter Motor is faulty.
 
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