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Neal, Dodge Mechanic
Category: Dodge
Satisfied Customers: 8351
Experience:  30 years experience in Dodge Chrysler and Plymouth
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ram 1500: goes into limp mode and lightning bolt light comes

Customer Question

04 ram 1500, 4x4, 5.7 hemi,auto trans. after 10 minutes at highway speeds (60 mph plus),it goes into limp mode and lightning bolt light comes on. it had a t/stat (running too cold ) and p/strg pres. switch code. replaced both. Check engine light is now off and NO codes have came back. the engine temp. is now warmer (normal).. But after 10 minutes on highway it would go into limp mode contiously. once i got off the highway it was fine. if i drive "city' not on highway it is fine.. ??????
Submitted: 5 years ago.
Category: Dodge
Expert:  Neal replied 5 years ago.

I'm Neal and I am here to assist you. Only accept when you are happy with my assistance. If I can't help I will open your Question to other experts.


Can you check for codes again? and check for pending codes also, there should be something stored.

Customer: replied 5 years ago.
no current codes. but there is a P1618 stored in enhanced engine codes
Expert:  Neal replied 5 years ago.

Are there any aftermarket accesories on the truck?


How old is the battery?

Expert:  Neal replied 5 years ago.

I need to log off for to get lunch. Will be back

Customer: replied 5 years ago.
battery is 2008 , aftermrkt stereo
Expert:  Neal replied 5 years ago.
Do you have another battery you can try in order to rule the battery out as a cause?

It can happen that the battery will develop an intermittent internal short that can cause that. I'm not saying that is it for sure but it should be ruled out. if that it not it I can provide some more info on diagnostics for that code.
Customer: replied 5 years ago.
i will put a battery in it today and drive it tonight....and get back with u tomorrow.. if i loose this thread how do i continue it tomorrow..
Expert:  Neal replied 5 years ago.
You should be getting email notifications with a link, or you can save this link by emailing it to yourself or pasting it into a document and saving it.
Customer: replied 5 years ago.
Goodmorning. i put new battery in and drove on interstate. as soon as i got sbove 65 mph it went into limp mode,shifted to nutrl shut key off and restarted, it was ok as long as i keep it at 60 mph or lower... no engine light ,same p1618 code stored.. ??
Expert:  Neal replied 5 years ago.

That is too bad, that would have been the easy fix!!


This diagnostic will need to be done to determine the problem.



Ignition on.

When the PCM recognizes the Primary 5-volt Supply circuit voltage is varying too much to quickly. One Trip Fault. ETC light is flashing.

- Good trip equal to zero
- (F855) Primary 5-volt supply shorted to ground
- Sensor shorted to ground
- Internal sensor
- (F855) Primary 5-volt supply shorted to voltage
- (F855) Primary 5-volt supply circuit open