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Code P1798

Symptoms

• Check Engine Light is on

• Transmission may not shift properly

• Vehicle may go into limp mode

Common Causes

• Faulty Transmission Control Module (TCM)

• Corrupted EEPROM data

• Electrical issues such as poor connections or damaged wiring

Glossary

TCM: Transmission Control Module

EEPROM: Electrically Erasable Programmable Read-Only Memory

Related Codes

• P1795

• P1796

• P1797

Official description

Internal Transmission Control Module EEPROM Writing Error

Laymans terms

The car's computer, which helps control the transmission, is having trouble saving some important information. It's like when you try to save a game on your console, but it doesn't work.

Explanation

The Transmission Control Module (TCM) is unable to write data to its EEPROM, which is necessary for storing important transmission settings.

Technical description

The P1798 code indicates that the Transmission Control Module (TCM) has detected a failure in writing data to its EEPROM (Electrically Erasable Programmable Read-Only Memory). The EEPROM is a type of memory used to store critical data that the TCM needs to manage the transmission effectively. This error can prevent the TCM from functioning properly, leading to transmission issues.

Diagnosis steps

• Use an OBD-II scanner to confirm the P1798 code.

• Inspect the TCM and its connections for damage or corrosion.

• Test the electrical circuits related to the TCM for continuity and proper voltage.

Repair procedures

• Replace or reprogram the Transmission Control Module (TCM).

• Repair any damaged wiring or connectors.

• Clear the code and test drive the vehicle to ensure the issue is resolved.

Tools required

• OBD-II scanner

• Multimeter

• Basic hand tools

Estimated repair cost

$300 - $1,200

Difficulty level

Difficult

Commonly affected vehicles

• Chrysler Town & Country

• Dodge Grand Caravan

• Jeep Grand Cherokee

Preventive measures

• Regularly inspect and maintain the vehicle's electrical system.

• Avoid exposure of the TCM to moisture and extreme temperatures.

• Keep the transmission fluid clean and at the proper level.

Error code type

Transmission Control Module Issue

User experience recommendations

• Do not ignore the Check Engine Light.

• Have the vehicle diagnosed by a professional mechanic.

• Avoid driving the vehicle in harsh conditions until the issue is resolved.

Warranty information

Check if the vehicle's powertrain warranty covers the TCM.

Historical data

This code has been associated with vehicles that have a history of TCM failures, particularly in models from the early 2000s.

Urgency level

High – This issue can lead to significant transmission problems and should be addressed promptly.

Legal and safety notice

Driving with a malfunctioning transmission can be dangerous. Ensure repairs are conducted by a qualified technician.

Testing conditions

• Vehicle at operating temperature

• Transmission in drive

Component location

The Transmission Control Module is usually located near the transmission or under the dashboard.

FAQs

Q: Can I drive with a P1798 code?
A: It's not recommended as it can lead to further transmission damage.

Q: Will resetting the code fix the problem?
A: Resetting the code may temporarily clear the warning, but it won't fix the underlying issue.

Last updated: Mar 2, 2026 • Source: internal database
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