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Unread 06-25-2013, 01:23 PM   #1
brewcity1
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Bad alternator causing Transmission code?

Hey guys...would having a bad alternator and battery cause a transmission solenoid code?
I was told by my mechanic that my alternator is shot, and my battery is really low...this is causing the check engine light to come on resulting in a code for the transmission solenoid. Does this make sense to all you experts?
BTW...on my way home...the battery gauge dropped to 0, and my transmission wont shift out of 1st gear.
Thanks for the help guys!

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Unread 06-25-2013, 02:13 PM   #2
HighLonesome
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low system voltage can do all kinds of strange things
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Unread 06-25-2013, 02:14 PM   #3
98ZJOKC
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Yes, if the electrical system is not supplying enough voltage, solenoids and relays won't operate properly. Honk your horn. If the electrical system is too weak to make the horn sound normal (ie loud as heck), then it can be too weak to open solenoids.
BTW, I think all Jeep and Dodge 5.9L's came with the 150 amp alternator as original equipment. I think you'll want to spend the little extra $ over the 90 amp and 136 amp prices when you replace yours.
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Unread 06-25-2013, 02:34 PM   #4
brewcity1
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Originally Posted by 98ZJOKC View Post
Yes, if the electrical system is not supplying enough voltage, solenoids and relays won't operate properly. Honk your horn. If the electrical system is too weak to make the horn sound normal (ie loud as heck), then it can be too weak to open solenoids.
BTW, I think all Jeep and Dodge 5.9L's came with the 150 amp alternator as original equipment. I think you'll want to spend the little extra $ over the 90 amp and 136 amp prices when you replace yours.
Thank you for the info...I really appreciate it.
I couldnt find a 150 Amp alternator anywhere...so opted for the 136.
Hopefully the e-fan wont have any issues. I also heard that the 150 amp alternator was because of the Infinity amp...which I now bypass do to aftermarket radio.
Guess we'll see...thanks again!
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Unread 06-25-2013, 06:34 PM   #5
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Update

Hey guys...just replaced my battery and my alternator...check engine light is still on, and the battery gauge just dropped to 0 and the check gauges light came on after 2 minutes of driving. Battery gauge never got to center. Transmission still didnt shift out of 1st.
What the heck is going on????
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Unread 06-25-2013, 06:49 PM   #6
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Raise the hood and find the compartment that holds your relays (on mine, it's passengers side, towards the front of the vehicle next to the battery). Find the one for the Transmission (TCU) and pull it out. Then start in L1 and when you hit about 20 to 25mph shift up to Drive. If your transmission shifts to 3rd, then at least you know it's only an electrical problem and has nothing to do with the transmission's mechanics.

Are there 5V regulators in these vehicles? Anyone know? That may be from the 80's and before.
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Unread 06-25-2013, 07:59 PM   #7
brewcity1
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Raise the hood and find the compartment that holds your relays (on mine, it's passengers side, towards the front of the vehicle next to the battery). Find the one for the Transmission (TCU) and pull it out. Then start in L1 and when you hit about 20 to 25mph shift up to Drive. If your transmission shifts to 3rd, then at least you know it's only an electrical problem and has nothing to do with the transmission's mechanics.

Are there 5V regulators in these vehicles? Anyone know? That may be from the 80's and before.
Thanks...I'll give that a try...but my voltage is still really low at start, and then drops to 0 and check gauges light comes on. Check engine light is on as well.
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Unread 06-25-2013, 08:41 PM   #8
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Well...I just reconnected everything from the alternator and the battery, and used die-electric grease on the battery terminals. Checked all the grounds, and re-tightened them. Cleaned the fuse box cables, and used die-electric grease on those as well...started her up, and the voltage is still low, and the check engine light is on.
I am going to take it back to my mechanic tomorrow morning, as I have NO idea what the heck is going on. I am totally stumped.
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Unread 06-25-2013, 09:46 PM   #9
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I know on some older chrysler vehicles that the voltage regulation is controlled by the pcm and can go bad causing a no charge situation. Is it the same for odb2 jeeps?
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Unread 06-25-2013, 10:06 PM   #10
brewcity1
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Originally Posted by jm8881 View Post
I know on some older chrysler vehicles that the voltage regulation is controlled by the pcm and can go bad causing a no charge situation. Is it the same for odb2 jeeps?
I have been reading through some threads, and found this as well. However...here is the situation...with my old battery and alternator...I never had this issue or a CEL on. I got my new cat and muffler installed, and it wouldnt start. My mechanic said it was a a bad wire harness from the new O2 sensor that was the cause (blowing a 20A fuse). Then it had a check engine light on from a code for the transmission solenoid. He said it was because of a bad alternator and battery. I just replaced both tonight...and still have the CEL on, and the voltage is low...then drops to 0 and the check gauges light comes on. So...I dont think its the PCM...because this just started happening after my new cat and muffler was put on.
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Unread 06-26-2013, 05:56 AM   #11
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Just a shot in the dark - battery temp sensor gone bad/grounded out? This causing the PCM to cut voltage from the alternator to the battery in order to save the battery from overcharging?
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Unread 06-26-2013, 06:47 AM   #12
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Have you pulled the codes to see what comes up?
Check for output signal to the field term on the alternator and see what voltage you are getting.
I think the field is turned on by the pcm by grounding it. If you have access to dvm you can check regulation by placing one prob on ve+ on the other on the field control on the back of the alt. to see if it is reg properly
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Unread 06-26-2013, 07:06 AM   #13
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Have you pulled the codes to see what comes up?
Check for output signal to the field term on the alternator and see what voltage you are getting.
I think the field is turned on by the pcm by grounding it. If you have access to dvm you can check regulation by placing one prob on ve+ on the other on the field control on the back of the alt. to see if it is reg properly
The code that popped up was for a transmission shift solenoid, or something along those lines. Mechanic said it was because of a bad alternator and low voltage. Obviously that not the case!
Its back at the shop...guess we'll see what he says. BTW..the 9er never died...but it was a short 15 minute trip...never shifted out of 1st gear either.
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Unread 06-26-2013, 07:06 AM   #14
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Originally Posted by 98ZJOKC View Post
Just a shot in the dark - battery temp sensor gone bad/grounded out? This causing the PCM to cut voltage from the alternator to the battery in order to save the battery from overcharging?
Thanks...I'll have him check this out.
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Unread 06-26-2013, 09:05 AM   #15
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Quote:
Originally Posted by brewcity1 View Post
The code that popped up was for a transmission shift solenoid, or something along those lines. Mechanic said it was because of a bad alternator and low voltage. Obviously that not the case!
Its back at the shop...guess we'll see what he says. BTW..the 9er never died...but it was a short 15 minute trip...never shifted out of 1st gear either.
Did you try charging the battery up first to see if the truck shifts out of first gear?
Solenoids and electronics act funny when the voltage is to low.
I agree with the other poster here; check the battery sensor.
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