Service bulletin 01-010-16-3185

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	10093127
Published by NHTSA	2017-02-28
Manufacturer's number	01-010-16-3185
Manufacturer's date	2016-04-07
NHTSA component	ENGINE

NHTSA's summary

SOME VEHICLES MAY EXPERIENCE THE CHECK ENGINE LIGHT ON WITH DTC P0421:00 (CATALYTIC CONVERTER SYSTEM) WITH-OUT EXPERIENCING POOR ENGINE PERFORMANCE OR MISFIRE (MITSUBISHI PCM ONLY).THIS IS CAUSED BY IMPROPER CONTROL LOGIC OF THE PCM THAT MAY DETECT FALSE ERROR OF THE A/F SENSOR, RESULTING IN FALSE DETECTION OF P0421. TO CORRECT THE PROBLEM, THE CONTROL LOGIC OF THE PCM HAS BEEN CHANGED.CATALYST MON-ITOR FUNCTION EXPLANATION•THE PCM MONITORS THE OXYGEN STORAGE AMOUNT PROPORTIONAL TO CATALYTIC CONVERTER PURIFICATION CHARACTERISTIC.•THE PCM STARTS TO MONITOR AFTER RECOVERY (FUEL INJECTION STARTS) FROM FUEL CUT CONTROL.•THE PCM TEMPORARILY CHANGES THE TARGET AIR/FUEL RATIO TO RICH AT FUEL CUT RECOVERY, AND DETECTS THE RESPONSE TIME UNTIL THE HO2S OUTPUT SIGNAL OUTPUTS THE VOLTAGE ON THE RICH SIDE. IF THE CATALYTIC CONVERTER PURIFICATION CHARACTERISTIC DETERIORATES, THE AMOUNT OF THE TIME UNTIL THE HO2S DETECTS THE VOLTAGE ON THE RICH SIDE IS SHORTER COMPARED TO THE NORMAL PURIFICATION CHARACTERISTIC AS SHOWN. THE PCM DETECTS A CATALYTIC CONVERTER MALFUNCTION USING THIS CHARACTERISTIC.

The document

No address for NHTSA's copy can be built for this communication. Ask the dealer for it by the manufacturer's number.

Components

Engine

Trouble codes named

P0421

Vehicles listed
MAZDA CX-5	2014, 2015, 2016
MAZDA MAZDA3	2014, 2015
MAZDA MAZDA6	2014, 2015, 2016

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
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.
SA-052-25	2025-12-05. Service bulletin. Some customer's might state that they notice fluid or oil leaking/dripping on the ground when the vehicle is parked. For this concern, inspect the vehicle for any trace of a fluid or oil leak and use the following examples as a guide to determine if it is severe enough to require a repair, or just to clean the area and monitor it at the next service. Examples of residue or seepage that may not be considered a leak and that may not require repair based on splash shield inspection.
SA-057-24	2024-09-04. Service bulletin. 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.
SA-052-24	2024-09-04. Service bulletin. Some customer's might state that they notice fluid or oil leaking/dripping on the ground when the vehicle is parked. For this concern, inspect the vehicle for any trace of a fluid or oil leak and use the following examples as a guide to determine if it is severe enough to require a repair, or just to clean the area and monitor it at the next service.
SA-011-24	2024-03-06. Service bulletin. 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.
SA-032-23a	2023-11-02. Service bulletin. 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.
SA-035-23	2023-07-05. Service bulletin. Some customers may complain of a lack of power under heavy load without any warning lights or DTCs. This concern may be due to a loose or detached hood weatherstrip, which can cause a blockage or restriction in the air intake system.
01-008-23	2023-07-05. Service bulletin. Some vehicles may exhibit oil leakage from the drive belt auto tensioner and rattling noises from the engine compartment. This may be caused by insufficient sealing at the drive belt auto tensioner damper when the auto tensioner fully operates under both high ambient temperature and high load conditions. To eliminate this concern, the shape of the drive belt auto tensioner damper has been changed.