AutoCodes – RAM – P1790 RAM

P1790 RAM Code - Fault Immediately After Shift

Quick Answer

This Diagnostic Trouble Code (DTC) is set if the engine is running and the vehicle speed is more than 10 mph in Drive, and the Transmission Control Module (TCM) detects a Speed Ratio Code within 1.3 seconds after a shift event occurs. Common causes include Transmission has an internal mechanical problem. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P1790 RAM indicates Fault Immediately After Shift.
Common causes: Common causes include Transmission has an internal mechanical problem.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 438

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Nov 19, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1790 RAM Description

This Diagnostic Trouble Code (DTC) is set if the engine is running and the vehicle speed is more than 10 mph in Drive, and the Transmission Control Module (TCM) detects a Speed Ratio Code within 1.3 seconds after a shift event occurs. The existence of DTC P1790 indicates mechanical or hydraulic (not electrical) related problems. It should be noted, however, that all mechanical problems don't necessarily result in DTC P1790. When this DTC exists, diagnosing the system should be based on the associated DTC and only mechanical causes should be considered.

OBDII Code P1790 RAM - Fault Immediately After Shift - AutoCodes.com — P1790 RAM Code - Fault Immediately After Shift

What does this mean?

What are the Possible Causes of the DTC P1790 RAM?

Transmission has an internal mechanical problem

How to Fix the DTC P1790 RAM?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1790 RAM code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P1790 RAM Code

1. What does the OBDII code P1790 mean on a RAM vehicle?

P1790 indicates a "Fault Immediately After Shift," meaning the transmission control module (TCM) detected an issue following a gear shift.

2. What are the common symptoms of code P1790 in a RAM?

Symptoms may include harsh or delayed shifting, the transmission slipping, erratic gear changes, or the check engine light illuminating.

3. What causes the P1790 code to trigger?

Potential causes include a faulty transmission control module (TCM), damaged wiring or connectors, low or dirty transmission fluid, or a mechanical issue within the transmission.

4. Can driving with code P1790 damage my RAMâ€™s transmission?

Yes, ignoring the issue could lead to further transmission damage or unsafe driving conditions. It's best to address the problem promptly.

5. How is the P1790 code diagnosed?

A technician will use a scan tool to read the code, check the freeze frame data, inspect transmission fluid quality, and perform visual and electrical tests on transmission components.

6. Does low transmission fluid cause code P1790?

Yes, insufficient or contaminated transmission fluid can contribute to shifting issues and trigger the P1790 code.

7. Can a failing TCM cause P1790 to appear?

Yes, a malfunctioning transmission control module can fail to properly control shifts, leading to this fault code.

8. How do you fix the P1790 code on a RAM?

Repairs may involve replacing or reprogramming the TCM, repairing wiring or connectors, flushing and refilling transmission fluid, or addressing internal transmission issues.

9. Is a software update needed to fix code P1790?

In some cases, outdated TCM software can cause shifting faults. A software update may resolve the issue if no mechanical problems are found.

10. How much does it cost to repair the P1790 code on a RAM?

Costs vary depending on the root cause, but repairs may range from $100 for a fluid flush to $1,000+ for TCM replacement or significant transmission repairs.