Dodge Repair: 01 Dodge Ram: transmission wont down shift


Question
QUESTION: sometimes when i am driving and stop, the Trans won't shift back in to low by it self but it will go in to low manually . if i shut the truck off and restart it , it will work fine.

can you help me with this ?

the truck is a
2001 Dodge ram sport 1500
5.9L motor

Thank you
Dave

ANSWER: Hi Dave,
The best way to get a diagnosis is to use the built-in self-diagnostic capability in the transmission controller. The only way to do that is to use a plug-in code reader that goes into a socket under the dash. An independent repair shop will usually charge about $40 to do that. Ask then for the fault code numbers which are 4-digit numbers which are preceded with a P. Then ask what they mean and what is suggested to do. Then send me a follow-up question and tell me what you learned so we can compare that to the shop manual information and decide what is the best way to improve things. In the meantime check that the fluid level in the trans is correct.
Please read the PS (below) and respond to it.
Thanks,
Roland

---------- FOLLOW-UP ----------

QUESTION: nothing showes up on the scanner . says pass

Answer
Hi Dave,
Are you certain that the scanner that was used could access the transmission control module's memory? If not, try another shop.
What you described sounds like a condition that would have a cause that would set a code. Without a fault code one thing to try would be to do a power flush of all the transmission fluid and replace it with a Chrysler-approved fluid. Other than that, there are a number of ports on the transmission where pressure readings can be performed and compared with the accepted levels and that might point you toward the cause.
Please consider doing a rating and nomination.
Thanks,
Roland