Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
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.
The Transmission Control Module (TCM) is unable to write data to its EEPROM, which is necessary for storing important transmission settings.
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.
• Check Engine Light is on
• Transmission may not shift properly
• Vehicle may go into limp mode
• Faulty Transmission Control Module (TCM)
• Corrupted EEPROM data
• Electrical issues such as poor connections or damaged wiring
TCM: Transmission Control Module
EEPROM: Electrically Erasable Programmable Read-Only Memory
• 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.
• 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.
• OBD-II scanner
• Multimeter
• Basic hand tools
$300 - $1,200
Difficult
• Chrysler Town & Country
• Dodge Grand Caravan
• Jeep Grand Cherokee
• 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.
Transmission Control Module Issue
• 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.
Check if the vehicle's powertrain warranty covers the TCM.
This code has been associated with vehicles that have a history of TCM failures, particularly in models from the early 2000s.
High – This issue can lead to significant transmission problems and should be addressed promptly.
Driving with a malfunctioning transmission can be dangerous. Ensure repairs are conducted by a qualified technician.
• Vehicle at operating temperature
• Transmission in drive
The Transmission Control Module is usually located near the transmission or under the dashboard.
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.
High-End · Full-system diagnostics
A full-system bidirectional platform aimed at advanced DIY users and professional diagnostic workflows.
Network faults often require full-system access instead of a generic code reader alone.
View on Amazon
Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
View on Amazon
Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.