Workshop Manuals Factory service & repair Mazda

Mazda common faults and how to fix them

Faults that are well known on Mazda models we hold manuals for: what the owner notices, what causes it, and the pages in our manuals that cover the repair.

Mazda P0300: misfire from fouled spark plugs on the CX-7, Mazdaspeed3 and Mazdaspeed6

Symptoms

The check engine light comes on with P0300 (random misfire) or P0301 to P0304 (misfire on a single cylinder), and the engine may idle roughly. It is most likely on cars used mainly for repeated short journeys. It affects the 2.3 turbo (DISI) engine.

Cause

Mazda bulletin 01-046/10 covers the 2007–2009 CX-7 and Mazdaspeed3 and the 2006–2007 Mazdaspeed6. On repeated short trips, carbon builds up on the spark plugs and fouls them. Separately, bulletin 01-007/07 found that on the 2007 CX-7 a poorly fitted engine computer (PCM) connector, after earlier work, could cause P0201, P0204 or P0300 and a rough idle.

Fix

For carbon fouling, the Mazda P0300 bulletin burns the carbon off by running the engine with no load at 4,000 rpm for two minutes, twice. Don't clean the plugs with a wire brush, as that damages them; replace them if they are worn. If the PCM connector has been disturbed, check it is fully seated at the right angle, as the CX-7 misfire bulletin describes, and never force the halves together.

Repair instructions on this site

Sources: Mazda technical service bulletins 01-046/10 and 01-007/07.

Mazda6 cooling fan: fan control module failure and overheating (2003–2007)

Symptoms

The radiator cooling fan stops working, so the coolant temperature rises, especially in traffic, and the engine can overheat. Some cars make a noise from the fan module instead.

Cause

Mazda campaign SSP71 found that on certain Mazda6 models, a crack can form in the soldered part of an IC terminal in the cooling fan control module, giving poor continuity. The fan can then stop running. An earlier campaign, SSP60, also replaced the fan control module on early Mazda6 models.

Fix

Check with a Mazda dealer whether the campaigns have been carried out; the remedy is a new fan control module. If the fan doesn't run when the engine is hot or the air conditioning is on, test the fan, its fuse and the module before looking elsewhere. The Mazda6 cooling fan campaign describes the fault, and the Mazda6 fan control module campaign covers the earlier cars. Don't keep driving if the temperature gauge rises.

Repair instructions on this site

Sources: Mazda special service programs SSP71 (April 2007) and SSP60 (August 2004).

Mazda 3 problems: cold-start vibration and P0302 on the 2010 2.5 automatic

Symptoms

A vibration through the steering wheel or seat for about 30 seconds after the first start of the day, or the check engine light with P0302 (cylinder 2 misfire), sometimes with P0300 (random misfire).

Cause

Mazda bulletin 01-036/09 covers 2010 Mazda3 models with the 2.5 engine and automatic gearbox, built before 14 May 2009 to the California PZEV specification. When the swirl control shutter valve in the intake manifold is closed during a cold idle, too much clearance between the valve and the intake port makes combustion unstable.

Fix

Read the freeze-frame data stored with the misfire code and compare it with the bulletin's criteria. If they match, the Mazda 3 vibration bulletin replaces the intake manifold with the revised part listed. If not, carry on with normal misfire diagnosis: plugs, coils and injectors on cylinder 2.

Repair instructions on this site

Sources: Mazda technical service bulletin 01-036/09.