AutoCodes – Generic – U1077

U1077 Code - Invalid Or Missing Data For Primary Id

Quick Answer

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Common causes include Faulty Module that is not communicating, Module harness is open or shorted, 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: U1077 indicates Invalid Or Missing Data For Primary Id.
Common causes: Common causes include Faulty Module that is not communicating, Module harness is open or shorted, 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 3,921

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 Apr 22, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U1077 Description

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for State of Health monitoring. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. When a module does not associate an identification number with at least one critical parameter within 5 seconds of beginning serial data communication, the Diagnostic Trouble Code (DTC) is set.

OBDII Code U1077 - Invalid Or Missing Data For Primary Id - AutoCodes.com — U1077 Code - Invalid Or Missing Data For Primary Id

What does this mean?

What are the Possible Causes of the DTC U1077?

Faulty Module that is not communicating
Module harness is open or shorted
Module circuit poor electrical connection

How to Fix the DTC U1077?

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 U1077 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.

Need more information about the U1077 code?

Need more information on how to fix the U1077 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U1077 code diagnosed by a professional: Find a repair shop in your area

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 U1077 Code

1. What does the OBDII code U1077 mean?

U1077 indicates "Invalid or Missing Data for Primary ID," meaning the vehicle's communication network has detected incomplete or incorrect data from a primary module.

2. What are the common symptoms of the U1077 code?

Symptoms may include warning lights on the dashboard (e.g., check engine light), erratic vehicle performance, loss of communication with certain modules, or intermittent electrical malfunctions.

3. What causes the U1077 code to appear?

The code can be triggered by a faulty control module, poor wiring connections, damaged communication lines, or software bugs in the vehicle's network.

4. Can a weak battery cause the U1077 code?

Yes, a weak or failing battery can cause voltage irregularities that disrupt communication between control modules, leading to the U1077 code.

5. How is the U1077 code diagnosed?

A technician will use a scan tool to check for related codes, inspect the vehicle's communication network wiring, and test the affected modules for proper functionality.

6. Can I drive my vehicle with the U1077 code?

While the vehicle may still be drivable, ignoring the U1077 code can lead to further communication issues and potential safety risks.

7. How do you fix the U1077 code?

Repairs may involve inspecting and repairing wiring or connectors, reprogramming or replacing faulty control modules, or updating the vehicle’s software.

8. Can a software update resolve the U1077 code?

Yes, in some cases, a software update for the vehicle's control modules can resolve the code if it was caused by a programming issue.

9. How much does it cost to fix the U1077 code?

Repair costs vary depending on the root cause, but diagnostic testing typically costs $75–$150, with additional costs for parts and labor if repairs are needed.

10. Can the U1077 code reset itself?

If the issue is intermittent or resolves on its own (e.g., a loose connection is temporarily fixed), the code may clear after several drive cycles, though it’s best to have it inspected.