AutoCodes – Generic – U0178

U0178 Code - Lost Communication With Restraints System Sensor 'I'

Quick Answer

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. Common causes include Faulty Restraints System Sensor 'I', Restraints System Sensor 'I' harness is open or shorted, Restraints System Sensor 'I' 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: U0178 indicates Lost Communication With Restraints System Sensor 'I'.
Common causes: Common causes include Faulty Restraints System Sensor 'I', Restraints System Sensor 'I' harness is open or shorted, Restraints System Sensor 'I' 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 2,033

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 02, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code U0178 Description

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. Operating information and commands are exchanged among the devices. The devices have programmed information about what messages are needed to be exchanged on the serial data circuits. CAN bus uses two dedicated wires for communication. The wires are called CAN high and CAN low. When the CAN bus is in idle mode, both lines carry 2.5V. When data bits are being transmitted, the CAN high line goes to 3.75V, and the CAN low drops to 1.25V, thereby generating a 2.5V differential between the lines. Since communication relies on a voltage differential between the two bus lines, the CAN bus is NOT sensitive to inductive spikes, electrical fields, or other noise. The Diagnostic Trouble Code (DTC) sets when a periodic message from the Restraints System Sensor 'I' has not been received.

OBDII Code U0178 - Lost Communication With Restraints System Sensor 'I' - AutoCodes.com — U0178 Code - Lost Communication With Restraints System Sensor 'I'

What does this mean?

What are the Possible Causes of the DTC U0178?

Faulty Restraints System Sensor 'I'
Restraints System Sensor 'I' harness is open or shorted
Restraints System Sensor 'I' circuit poor electrical connection

How to Fix the DTC U0178?

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 U0178 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 U0178 code?

Need more information on how to fix the U0178 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U0178 code diagnosed by a professional: Find a repair shop in your area

Precautions for SRS “AIR BAG” and “SEAT BELT PRE-TENSIONER” Service

Never probe the electrical connectors on air bag, side air curtain modules or seat belts.
Never disassemble or tamper with safety belt buckle/retractor pretensioners, adaptive load limiting retractors, safety belt inflators, or probe the electrical connectors.
Do not use electrical test equipment to check SRS circuits unless instructed to in this Service Manual.
Before servicing the SRS, turn ignition switch OFF, disconnect both battery cables and wait at least 3 minutes. For approximately 3 minutes after the cables are removed, it is still possible for the air bag and seat belt pre-tensioner to deploy. Therefore, do not work on any SRS connectors or wires until at least 3 minutes have passed.

Failure to follow this instruction may result in the accidental deployment of these modules, which increases the risk of serious personal injury or death.

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.