2020 Mazda 3 Service and Repair Manual

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Covers all 2020 3 trims — Select Sedan 4-Door, Premium Sedan 4-Door, I Sport Hatchback 4-Door +9 more ·
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2020 Mazda 3 service and repair manual — a detailed, factory-style reference for maintenance, diagnostics, and repair. Use it to confirm correct procedures, specifications, and system coverage before you start work.

Designed for technicians and DIY owners, this manual helps you diagnose issues correctly, follow proven repair steps, and use wiring diagrams and system sections to track faults faster.

What’s included

  • Step-by-step repair procedures and service information
  • Specifications and reference data (where provided)
  • Electrical diagnostics with wiring diagrams
  • Coverage across major systems: engine, transmission/driveline, brakes, steering, suspension, HVAC, and more

Trims covered

  • Select Sedan 4-Door
  • Premium Sedan 4-Door
  • I Sport Hatchback 4-Door
  • Base Sedan 4-Door
  • Base Hatchback 4-Door
  • GS Sedan 4-Door
  • Premium Hatchback 4-Door
  • i Grand Touring Hatchback 4-Door
  • GT Sedan 4-Door
  • Preferred Sedan 4-Door
  • i Sedan 4-Door
  • i Grand Touring Sedan 4-Door
  • GX Sedan 4-Door
  • I Sport Sedan 4-Door
  • Preferred Hatchback 4-Door

Engines covered

  • 2.5L 2488CC 152Cu. In. l4 GAS DOHC Naturally Aspirated
  • 2.0L 1998CC 122Cu. In. l4 GAS DOHC Naturally Aspirated

Index / Table of contents

  • Body
  • Brakes
  • Chassis Electrical
  • Driveline
  • Engine Cooling
  • Engine Electrical
  • Engine Mechanical
  • Engine Performance & Emission Controls
  • Fuel System
  • General Information & Identification
  • Heating, Ventilation, & Air Conditioning
  • Hybrid & Electric Vehicle Systems
  • Steering
  • Suspension
  • Transmission, Clutch, & Transfer Case
  • Wiring Diagrams
NHTSA #19V90700019/12/2019Component: FORWARD COLLISION AVOIDANCE: AUTOMATIC EMERGENCY BRAKING

Mazda North American Operations (Mazda) is recalling certain 2019-2020 Mazda3 vehicles. The Smart Brake System (SBS) can falsely detect an obstacle while driving, activating the automatic emergency braking system and suddenly stopping the vehicle.

Consequence

Stopping the vehicle unexpectedly increases the risk of a crash.

Remedy

Mazda will notify owners, and dealers will update the SBS software. In addition, vehicles with certain production dates will receive an instrument cluster software update or replacement and a replacement owner's manual. These repairs will be performed free of charge. The recall began February 14, 2020. Owners may contact Mazda customer service at 1-800-222-5500, Option 4. Mazda's number for this recall is 4219L.

NHTSA #20V34600012/06/2020Component: SERVICE BRAKES, HYDRAULIC:FOUNDATION COMPONENTS:DISC:CALIPER

Mazda North American Operations (Mazda) is recalling certain 2020 CX-30 and Mazda3 vehicles. The front brake caliper mounting bolts may not have been tightened properly during assembly, possibly allowing the calipers to loosen.

Consequence

Loose brake calipers can reduce braking performance or interfere with wheel rotation, affecting vehicle handling. Either of these scenarios can increase the risk of a crash.

Remedy

Mazda will notify owners, and dealers will inspect the front brake caliper bolts, tightening them as necessary. If bolts are missing, the affected brake caliper will be replaced. Repairs will be performed free of charge. The recall began July 24, 2020. Owners may contact Mazda customer service at 1-800-222-5500, Option 4. Mazda's number for this recall is 4420F.

TSB #11033447

This service alert supersedes the previously issued service alert listed below. The changes are noted in Red text. SA-047/25 10/07/25 DESCRIPTION When the Telematics Control Unit (TCU) replacement is necessary due to a failure, use MDARS to

TSB #11033445

This SA supersedes the previously issued SA(s) listed below. The changes are noted in Red. SA-011/25 10/16/25 and 02/27/25 DESCRIPTION Some customers will report that their fuel door (AKA, fuel filler door, fuel lid, and fuel-filler lid) wa

TSB #11033115

DESCRIPTION Some customers may complain that the seat warmer does not operate when turning the ignition on while the seat is warm but when turning the ignition off then on again, the seat warmer begins to operate appropriately. DTCs B1030:1

TSB #11032104

DESCRIPTION Some vehicles may require the replacement of a damaged VIN plate or vehicle certification label. To obtain a replacement VIN plate (bulkhead-mounted and visible through the lower-left area of the windshield), contact DAG (Dealer

TSB #11032103

This Service Alert supersedes the previously issued SA listed below: The changes are noted in Red. SA-011/24 02/12/24, 06/06/24, 07/29/24 DESCRIPTION Mazda has developed factory recommended scheduled maintenance services that support all ma

TSB #11032102

This SA supersedes the previously issued bulletin(s) listed below. The changes are noted below in Red. SA-007/25 10/22/25, 06/02/25 and 02/03/25 DESCRIPTION The Mazda DCA-8000 is required for all warranty battery testing. If the Mazda DCA-8

TSB #11032101

This Service Alert supersedes the previously issued M-Tip(s) listed below. The changes are noted in Red text. MT-002/19 09/30/19 and 12/19/19 DESCRIPTION If an engine assembly is replaced after a catastrophic internal mechanical failure, cl

TSB #11032003

This bulletin supersedes the previously issued bulletin(s) listed below. The changes are noted in Red. 01-008/23 06/05/23 Some vehicles may exhibit rattling noises from the engine compartment and oil leakage from the drive belt auto tension

Showing the 8 most recent of 682 technical service bulletins on file with NHTSA.

03/13/20Component: TIRES

size 21545ZR18 93Y. replaced these oem tires with these from costco on feb 27 2025. in dec 5 2025 the tire developed a large bubble. miles bought was 27790. current miles 31212. per tire center steal belting was broken no signs of road hazard or other damage. the belt broke and rubber was stressed with " maybe a 1000 miles regaining before catastrophic failure." wear instrument showed they were literally showing new tires. states they were the 3rd michellin tires with dude wall bubbling that week. states could have caused severe accident. no warnings damage leaks or idicators. all mainten

02/19/20Component: POWER TRAIN

My Mazda3 began producing a chirp when shifting from 3rd to 4th gear (automatic transmission). The dealer stated that the car needed a new torque converter. At the time the car only 37,000 miles on it, quite low mileage for a torque converter to fail. Mazda has previously admitted to producing cars with faulty torque converters, as specified in Mazda TXXXXXX] ). While my car fit the description of both the problem and proposed fix, and also fell within the applicable models/VINs listed on the TSB, Mazda corporate HQ stated that my specific VIN was not covered by the TSB, and therefore the repa

11/18/20Component: SUSPENSION

I pulled into the driveway (at about 5 mph) of my passenger's home, when a very loud, metallic pop occurred somewhere inside my vehicle. I could not discern the problem by visually inspecting the car. Upon returning to my home, I arranged for the dealership to inspect the car's suspension. They found that both rear springs had snapped off from their lower vehicle attachment points. At the time of the incident, my car was less than 6 years old and had approximately 62500 total miles. I had the dealership replace both rear springs and associated attachment hardware. Prior to this failure,

11/16/20Component: STEERING,SUSPENSION

TSB 02-003/24 Car front suspension bolts corroded and making metal on metal sounds during turning and braking

07/08/20Component: EQUIPMENT

See attached document for complaint.

07/17/20Component: SEAT BELTS

Passenger seat belt won’t retract and remains in a locked state.

06/16/20Component: ELECTRICAL SYSTEM,EXTERIOR LIGHTING,LANE DEPARTURE

Google search shows Mazda has common problem with their front sensing camera, people are reporting the issue for different Mazda models across the board for the last few years including newer models as well. My car display shows few malfunction warning messages. Following captured from MyMazda app. 1. Forward sensing camera malfunction. i-ACTIVESENSE advanced safety and driver support systems may not operate correctly. 2. High Beam Control System is disabled. Automatic switching between high and low beams is unavailable.

09/26/20Component: FORWARD COLLISION AVOIDANCE

While driving on a residential street the automatic emergency braking system activated and brought the car to a very abrupt stop but there was nothing in the front of the car to activate the system. There were no cars in the on-coming lane and no cars in the lane beside my car. When the car stopped the Brake warning appeared in the windshield and a warning tone sounded. It was in the early evening and it was raining. Fortunately there were no cars behind me so there were no injuries. I took the car to the Mazda dealership and upon inspection they noted that the radar system associated with the

Showing the 8 most serious of 31 complaints filed with NHTSA.

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