Service bulletin 01-006-26

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

The communication, as NHTSA indexes it (as of 2026-10-19)
Type	Service bulletin
NHTSA id	11030600
Published by NHTSA	2026-04-02
Manufacturer's number	01-006-26
Manufacturer's date	2026-03-11
NHTSA component	ENGINE; UNKNOWN OR OTHER
Manufacturer's system	Cooling System

NHTSA's summary

Some customers may experience the check engine light on with DTC P0126:00 (Thermostat stuck open) stored. This is due to improper PCM logic control. To eliminate the concern, the PCM control software has been modified. REPAIR PROCEDURE 1. Verify the customer concern. 2. Reprogram the ECU with the Mazda Modular Diagnostic System (M-MDS), using Mazda Diagnostic and Repair Software (MDARS). Refer to MDARS ECU Reprogramming Procedure. NOTE: Be sure to submit Diagnostic Information (ODR) data as it is a required item and will be checked during warranty claim submission. Instructions can be found under M-MDS -> MDARS (Uploading Diagnostic Information (ODR) Data). 3. Clear any other DTCs. 4. Verify the repair by starting the engine (READY ON) and confirming there is no CHECK ENGINE light ON or abnormal warning lights present.

The document

The document is the manufacturer's. This site does not hold it. NHTSA files a document at one of these two addresses; we have not asked NHTSA which.

Components

Engine

Trouble codes named

P0126

Vehicles listed
MAZDA CX-30	2026
MAZDA MAZDA3	2026

Listing a model year does not mean every vehicle of it is concerned: the document says which.

Other bulletins for the same vehicles and component
DRW59 Warr a	2026-10-03. Service campaign. Subject: Notification of Dealer Re-Work (DRW59) – 2026MY CX-30 and 2026MY Mazda3 - Check Engine Light On With DTC P0126:00 Dear Mazda Dealer Colleagues, Mazda Motor Corporation has decided to conduct a Dealer Re-Work on certain 2026MY CX-30 and Mazda3 vehicles. Concern Outline: On certain subject vehicles, the check engine light may illuminate with DTC P0126:00 (Thermostat stuck open) stored due to improper PCM control logic. Repair Outline: Reprogram the PCM with the Mazda Modular Diagnostic System (M-MDS), using Mazda Diagnostic and Repair Software (MDARS) by following TSB 01-006/26 repair instructions. ACTION ITEM - STOP DELIVERY: All affected vehicles in inventory can be sold but not delivered until repaired. There are approximately 17,942 new vehicles in dealer stock and/or in transit to dealers. All affected dealer inventory types with this DRW must be repaired prior to delivery. The number of affected units at your dealership can be seen in Inventory & Sales 2.0 in eMDCS and a VIN list (via an internal MNAO campaign reporting) will also be provided to your District Service Manager by 5pm (Pacific Time) on the date this dealer email is sent. Owner Notification: There is no Owner Notification with this or any Dealer Re-Work. PARTS INFORMATION: There are no parts required for this repair.
SA-038-26a	2026-09-04. Service bulletin. This Service Alert supersedes the previously issued service alert listed below. The changes are noted in Red text. SA-038/26 06/15/26 DESCRIPTION Some customers may complain about any of the following: 1. Infotainment Center Display does not provide the Authorization Code (OTP) during the MyMazda App Connected Vehicle enrollment. 2. Remote functions inoperative. Engine Start / Stop Door Lock / Unlock Lights ON / OFF Climate Control 3. MAZDA CONNECT connected vehicle reception strength icon shows "X" or " ". Index MAZDA CONNECT 2 Center Display Status Icon MAZDA CONNECT 3 Center Display Status Icon Remote Engine Start Will Not Function Remote Engine Start Function Will turn engine OFF Customer Subscription Status TCU Communication Line Status
SA-042-26	2026-07-03. Service bulletin. This Service Alert supersedes the previously issued SAs listed below. The changes are noted in Red text. SA-017/25 12/16/25, 09/08/25, 07/14/25, 05/15/25 and 03/21/25 DESCRIPTION Mazda Connect Frequently Asked Questions (FAQ) Index General Questions MAZDA CONNECT Indication Setup and Getting Started Dealer Processes Registration / Enrollment / Take-Over Customer Subscription Status WI-FI General Informatio Opening the TCU Communication Line WI-FI How-To Conditions for Remote Engine Start Will Not Function WI-FI Trial Period Conditions for Remote Engine Start Function Will turn engine OFF Interacting With The App TCU Communication Line Status Service Issues Educational Videos Troubleshooting Resources MyMazda App Error Codes Customer Opt-Out
SA-041-26	2026-07-03. Service bulletin. This SA supersedes the previously issued SA(s) listed below. The changes are noted in Red. SA-061/25 12/17/25 DESCRIPTION If you encounter any type of electrical concern (e.g, dead battery, engine no start, DTC(s) stored...), interview the customer before proceeding with normal MGSS diagnosis by asking if any aftermarket devices have been installed. Aftermarket devices may be the cause of the electrical concern. Below are a few examples of unusual electrical concerns caused by aftermarket devices. Examples: 1. Devices connected to the DLC-2 (battery discharge/DTC stored) 2. Devices plugged into the 12V outlet 3. GPS tracking device (engine no start/battery discharge) 4. Dash cam (DTC stored) 5. Non-certified USB cable (Apple Carplay™/ Android Auto™ will not connect) 6. Over-sized wheels/tires (incorrect GPS location) 7. DTC C0023:14 8. Decorative trim and/or cover on the START/STOP ENGINE button Example 1: Some electrical devices connected to the DLC-2 connector by insurance or mobile phone companies may cause: Battery discharge. The device may disrupt the CAN system battery saver mode. • IDS/MMDS will not communicate with the vehicle due to poor DLC-2 connection. The aftermarket device may cause DLC-2 female terminals to spread open.
SA-029-26	2026-05-05. Service bulletin. 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 major vehicle systems. Mazda recommends dealers follow the scheduled maintenance tables as cited in the vehicle-specific workshop manual or owner's manual. Services performed outside of Mazda's factory scheduled maintenance are not recommended. These services are unnecessary and create unneeded expenses for your customers. SCHEDULED MAINTENANCE Refer to the applicable Workshop Manual or Owner's Manual for vehicle -specific manufacturer scheduled maintenance. Workshop Manual - Refer to section 00-00 SCHEDULED MAINTENANCE. Owner's Manual - Refer to section 8 Maintenance and Care. b. Note: Please refer to the information below outlining the services not included in Mazda's Factory Scheduled Maintenance: IMPORTANT: Recommending fluid flushes when not necessary can lead to customer confusion and dissatisfaction. Fluid flushing for preventive maintenance purposes is strongly discouraged, unless otherwise specified in a published procedure (Owner’s Manual, Workshop Manual, Technical Service Bulletin, etc.).
SA-026-26	2026-05-05. Service bulletin. 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, clean the intake manifold internally before installing a replacement engine assembly. If the intake manifold is not cleaned properly, the replacement engine may fail prematurely. Metallic debris from the old engine (with catastrophic internal mechanical failure) may rest inside the intake manifold. When the new engine assembly is installed, debris in the intake manifold will be ingested into the new engine and cause internal damage. Clean the intake manifold internally to remove any debris from old engine before installing the new replacement engine assembly. If the intake manifold cannot be properly cleaned internally, replace it.
DRW59 Warranty	2026-04-04. Service campaign. Subject: Notification of Dealer Re-Work (DRW59) – 2026MY CX-30 and 2026MY Mazda3 - Check Engine Light On With DTC P0126:00 Dear Mazda Dealer Colleagues, Mazda Motor Corporation has decided to conduct a Dealer Re-Work on certain 2026MY CX-30 and Mazda3 vehicles. Concern Outline: On certain subject vehicles, the check engine light may illuminate with DTC P0126:00 (Thermostat stuck open) stored due to improper PCM control logic. Repair Outline: Reprogram the PCM with the Mazda Modular Diagnostic System (M-MDS), using Mazda Diagnostic and Repair Software (MDARS) by following TSB 01-006/26 repair instructions. ACTION ITEM - STOP DELIVERY: All affected vehicles in inventory can be sold but not delivered until repaired. There are approximately 17,942 new vehicles in dealer stock and/or in transit to dealers. All affected dealer inventory types with this DRW must be repaired prior to delivery. The number of affected units at your dealership can be seen in Inventory & Sales 2.0 in eMDCS and a VIN list (via an internal MNAO campaign reporting) will also be provided to your District Service Manager by 5pm (Pacific Time) on the date this dealer email is sent. Owner Notification: There is no Owner Notification with this or any Dealer Re-Work. PARTS INFORMATION: There are no parts required for this repair.
DRW59 Repair	2026-04-04. Service campaign. Subject: Notification of Dealer Re-Work (DRW59) – 2026MY CX-30 and 2026MY Mazda3 - Check Engine Light On With DTC P0126:00 Dear Mazda Dealer Colleagues, Mazda Motor Corporation has decided to conduct a Dealer Re-Work on certain 2026MY CX-30 and Mazda3 vehicles. Concern Outline: On certain subject vehicles, the check engine light may illuminate with DTC P0126:00 (Thermostat stuck open) stored due to improper PCM control logic. Repair Outline: Reprogram the PCM with the Mazda Modular Diagnostic System (M-MDS), using Mazda Diagnostic and Repair Software (MDARS) by following TSB 01-006/26 repair instructions. ACTION ITEM - STOP DELIVERY: All affected vehicles in inventory can be sold but not delivered until repaired. There are approximately 17,942 new vehicles in dealer stock and/or in transit to dealers. All affected dealer inventory types with this DRW must be repaired prior to delivery. The number of affected units at your dealership can be seen in Inventory & Sales 2.0 in eMDCS and a VIN list (via an internal MNAO campaign reporting) will also be provided to your District Service Manager by 5pm (Pacific Time) on the date this dealer email is sent. Owner Notification: There is no Owner Notification with this or any Dealer Re-Work. PARTS INFORMATION: There are no parts required for this repair.
DRW59 Dlr Ltr	2026-04-04. Service campaign. Subject: Notification of Dealer Re-Work (DRW59) – 2026MY CX-30 and 2026MY Mazda3 - Check Engine Light On With DTC P0126:00 Dear Mazda Dealer Colleagues, Mazda Motor Corporation has decided to conduct a Dealer Re-Work on certain 2026MY CX-30 and Mazda3 vehicles. Concern Outline: On certain subject vehicles, the check engine light may illuminate with DTC P0126:00 (Thermostat stuck open) stored due to improper PCM control logic. Repair Outline: Reprogram the PCM with the Mazda Modular Diagnostic System (M-MDS), using Mazda Diagnostic and Repair Software (MDARS) by following TSB 01-006/26 repair instructions. ACTION ITEM - STOP DELIVERY: All affected vehicles in inventory can be sold but not delivered until repaired. There are approximately 17,942 new vehicles in dealer stock and/or in transit to dealers. All affected dealer inventory types with this DRW must be repaired prior to delivery. The number of affected units at your dealership can be seen in Inventory & Sales 2.0 in eMDCS and a VIN list (via an internal MNAO campaign reporting) will also be provided to your District Service Manager by 5pm (Pacific Time) on the date this dealer email is sent. Owner Notification: There is no Owner Notification with this or any Dealer Re-Work. PARTS INFORMATION: There are no parts required for this repair.
SA-014-26	2026-04-02. Service bulletin. This Service Alert supersedes the previously issued SA(s) and TSB(s) listed below: The changes are noted in Red. SA-035/24 05/31/24 DESCRIPTION There is a concern that some water pumps are being replaced that are not faulty, due to signs of a very small coolant leak from the bleed hole. This Service Alert is to inform you about the water pump sealing mechanism and the criteria if replacement is necessary or not. A mechanical seal (A) is used for the water pump. This mechanical seal can seal coolant (B) by sliding a mating ring (C) against a seal ring (D). When the sliding surface temperature of the mechanical seal is more than 248 °F (120 °C) while driving, a small amount of steam (E) is leaked and bleeds through the bleeding hole (F). After drying, the steam leaves a green coolant deposit near the water pump bleed hole (F). This is a normal condition and does not require water pump replacement. The water pump should only be replaced if there is an accumulation of crystallized coolant near the bleed hole. When you encounter a water pump with coolant seepage marks, decide to replace it or not based on the following criteria using sample photos. NOTE: During the initial period of use, the sliding surfaces of the seals may not yet be fully settled, which can temporarily increase the amount of leakage. Continued use will allow the surfaces to settle, reducing the leakage. Replacing parts that are already settled with new ones will increase the leakage again until the new parts become conditioned. Therefore, replacement should be avoided in this initial period of use. As a guideline, this applies to vehicles with less than 1,860 miles (3000 km) of mileage.