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2022 Ram 3500 Longhorn - Transmission Limp Mode & P07xx Codes

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Dan C. · rep 0 · May 22, 3:30 AM · 1 replies · solved · Question

Vehicle: 2022 Ram 3500 Longhorn

Hi all,

My 2022 Ram 3500 Longhorn (6.7L Cummins, Aisin transmission) with only 35,000 miles just went into limp mode! The Check Engine Light is on, and it feels like it's stuck in a single gear, maybe 3rd or 4th. I scanned it and got a few codes, primarily P0731 (Gear 1 Incorrect Ratio) and P0700 (Transmission Control System Malfunction).

This is a heavy-duty truck, and I rely on it for towing. I'm really concerned about a transmission issue at such low mileage. I haven't noticed any slipping or harsh shifts before this happened.

What could be causing this? Is it likely a sensor, or am I looking at a major transmission problem? Any insights from other Aisin owners would be great.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:30 AM

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ClearTheCode admin answer:

Experiencing limp mode and P07xx codes on your 2022 Ram 3500 Longhorn with the Aisin transmission is definitely concerning, especially at 35,000 miles. The P0700 code is a generic indicator that the Transmission Control Module (TCM) has detected a fault, and the P0731 (Gear 1 Incorrect Ratio) points to a specific issue within the transmission's operation.

Here are the common causes for these symptoms:

  1. Transmission Fluid Issues:
    • Low Fluid Level: Even a slightly low fluid level can cause pressure issues and incorrect gear ratios. Check the fluid level according to your owner's manual (Aisin transmissions often have specific checking procedures).
    • Contaminated/Old Fluid: While less likely at 35k miles, extremely dirty or burnt fluid can cause problems. Inspect the fluid for color and smell.
  2. Speed Sensors: The transmission relies on input and output speed sensors to determine gear ratios. A faulty sensor can send incorrect data to the TCM, leading it to believe a gear ratio is incorrect and triggering limp mode.
  3. Solenoid Issues: The transmission uses solenoids to control fluid flow to engage different gears. A stuck or failing solenoid can prevent proper gear engagement.
  4. Wiring/Connector Problems: Damaged wiring or a loose/corroded connector to the TCM or transmission sensors can interrupt communication and cause erroneous readings.
  5. Internal Transmission Mechanical Failure: While less common at this mileage, issues like worn clutch packs, valve body problems, or other internal mechanical failures can lead to incorrect gear ratios and limp mode.

What to do:

  • Check Transmission Fluid: This is the easiest first step. Ensure it's at the correct level and looks clean.
  • Inspect Wiring: Visually check the wiring harness going to the transmission for any obvious damage or loose connections.
  • Clear Codes and Retest (Cautiously): Sometimes, a transient electrical glitch can cause these codes. Clear them and drive gently to see if they return immediately. If they do, do not continue driving extensively in limp mode.

When to see a shop:

Given the complexity of modern transmissions, especially the Aisin, and the potential for serious damage, it's highly recommended to have your Ram serviced by a dealership or a transmission specialist as soon as possible. Driving extensively in limp mode can exacerbate the problem. A professional will have advanced diagnostic tools to read specific Aisin transmission codes, monitor live data from sensors and solenoids, and accurately pinpoint the root cause before recommending costly repairs.

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