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U18AC Cadillac Code - Transmission Range Control Module Lost Communication With Chassis Control Module On Chassis Expansion CAN Bus

Quick Answer

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Chassis Control Module, Chassis Control Module harness is open or shorted, Chassis Control Module circuit poor electrical connection. 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: U18AC Cadillac indicates Transmission Range Control Module Lost Communication With Chassis Control Module On Chassis Expansion CAN Bus.
Common causes: Common causes include Faulty Chassis Control Module, Chassis Control Module harness is open or shorted, Chassis Control Module circuit poor electrical connection.
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 2,119

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 Jun 08, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U18AC Cadillac Description

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the devices. The devices have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver device as an availability indication of the transmitter device. Each message contains the identification number of the transmitter device. The Diagnostic Trouble Code (DTC) will set a supervised periodic message that includes the transmitter device availability that has not been received.

OBDII Code U18AC Cadillac - Transmission Range Control Module Lost Communication With Chassis Control Module On Chassis Expansion CAN Bus - AutoCodes.com — U18AC Cadillac Code - Transmission Range Control Module Lost Communication With Chassis Control Module On Chassis Expansion CAN Bus

What does this mean?

What are the Possible Causes of the DTC U18AC Cadillac?

Faulty Chassis Control Module
Chassis Control Module harness is open or shorted
Chassis Control Module circuit poor electrical connection

How to Fix the DTC U18AC Cadillac?

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 U18AC Cadillac 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 U18AC Cadillac Code

1. What are common symptoms of the U18AC OBDII code in a Cadillac related to transmission range control module communication loss?

Symptoms may include shifting issues, transmission slipping, loss of power, and the transmission being stuck in a single gear.

2. What are possible causes of the U18AC OBDII code indicating a communication problem between the transmission range control module and chassis control module?

Possible causes include faulty wiring or connectors, a malfunctioning transmission range control module, issues with the chassis control module, or a problem with the CAN bus communication network.

3. How can I diagnose the U18AC OBDII code in my Cadillac related to the transmission range control module communication issue?

Diagnosis involves using a professional OBDII scanner to retrieve the code, checking the wiring and connectors for any signs of damage, and testing the communication between the transmission range control module and chassis control module.

4. What are some repair tips for resolving the U18AC OBDII code in a Cadillac?

Repair tips may include repairing or replacing damaged wiring or connectors, reprogramming or replacing the transmission range control module, addressing any issues with the chassis control module, and ensuring proper communication on the CAN bus network.

5. Can driving with the U18AC OBDII code present cause further damage to my Cadillac?

Continued driving with this code present can potentially cause further damage to the transmission system, leading to more severe issues over time. It is recommended to address the problem promptly.

6. Is it safe to continue driving my Cadillac if the U18AC code related to transmission range control module communication loss appears intermittently?

It is not recommended to drive the vehicle if the code appears intermittently, as it indicates an ongoing communication problem that can affect the performance and safety of the transmission system.

7. How much does it typically cost to repair the U18AC OBDII code in a Cadillac?

The cost of repairing the U18AC code can vary depending on the exact cause of the issue, the extent of the repairs needed, and labor costs. It is advisable to consult with a professional mechanic for an accurate estimate.

8. Can I reset the U18AC OBDII code in my Cadillac using an OBDII scanner?

Resetting the code using an OBDII scanner may temporarily clear the code, but if the underlying communication issue between the transmission range control module and chassis control module is not addressed, the code is likely to reappear.

9. Will the U18AC OBDII code in a Cadillac cause the vehicle to fail an emissions test?

If the U18AC code is related to a communication problem between the transmission range control module and chassis control module, it may not directly cause the vehicle to fail an emissions test. However, it is essential to address the issue promptly to ensure proper vehicle operation.

10. Can I repair the U18AC OBDII code in my Cadillac myself, or should I seek professional assistance?

Due to the complexity of diagnosing and repairing communication issues between modules in a vehicle, it is recommended to seek professional assistance from a qualified mechanic or dealership to properly address the U18AC OBDII code in your Cadillac.