Electronic Diagnostics: Mazda6 2.0 petrol
Tracing and fixing faults in electronic engine management systems
Well received by the public and the press for its performance and practicality, the Mazda6 also has a good reputation for reliability.
Kim Henson and Edward Haggar investigate whether this extends to its diagnostic aspects.
The first-generation Mazda6, designated GG1 and essentially derived from the 626, made its international debut in 2002. This well-respected model was sold in four-door saloon, five-door hatchback and five-door estate forms, and with a variety of engine/transmission options. Second-generation models arrived in 2007, launched at that year’s Frankfurt Motor Show and built on Mazda’s GH chassis. As with other Mazdas, the car has many design/component links with contemporary Fords.
The second-generation cars were sold in four-door saloon, five-door hatchback and estate versions and were widely praised for their dynamic qualities, as well as practicality for family use. Engine choices were 1.8-, 2.0- and 2.5-litre petrol units, plus a 2.0-litre diesel (a 2.2-litre joined the line-up from 2009).
A facelift in 2010 resulted in frontal restyling and interior upgrades. These cars were well-equipped and make good secondhand buys today. The thirdgeneration GJ was available from 2012.
Our vehicle for this feature is one of the second-generation 2.0-litre fourcylinder models, dating from September 2009. Guiding us through this petrol engine is Edward Haggar.
Compared to other modern cars, access around the Mazda6 engine is very good. Before carrying out any diagnostic work, it is worth checking the service history of the vehicle and taking a close look at the auxiliary drivebelt. If the belt is showing signs of a line on its external surface and is turning brown in colour, it is on borrowed time, so renew it as soon as possible.
Note that this engine incorporates a timing chain, rather than a belt, but problems can arise if regular oil and filter changes are not carried out. Renew both every 6000 miles or six months, whichever comes first, to guard against future trouble.
LOW BATTERY VOLTAGE
With our first fault on this Mazda6, the engine may be running in ‘limp-home’ mode, with the engine malfunction lamp on the dash illuminated. Fault codes ‘P0140’, ‘P0571’, ‘P0600’ and ‘P2101’ may be stored, relating to a faulty battery or low voltage.
Recharging the battery may restore normal running, after which the stored fault codes need to be cleared, but the problem will recur if the battery or charging system is weak and the voltage level falls again. In this case, the charging system will need to be repaired and/or a new battery fitted.
POOR EARTH CONNECTION
Our second fault with this Mazda manifests itself in the form of occasional non-starting. This may be due to corrosion or dirt adversely affecting the earth connection on the left-hand suspension turret. Often, if you hold the cable and move it from side to side, the engine will then start.
Dismantling the joint, carefully cleaning all contact faces and reassembling the earth connection components, using a silicone/grease product for future protection, will usually cure the trouble. However, if the corrosion is severe, it may be necessary to renew the earth cable/connector.
For owners, it’s heartening to know that Mazdas, and Japanese cars in general, are usually pretty good electrically-speaking.
Fault 3 TIMING CHAIN ISSUES
If engine oil and filter changes are ignored, eventually the timing chain tensioner will be starved of oil, resulting in the chain becoming slack and jumping the sprockets. This often occurs when trying to start the engine; if it is already running, it will stop and refuse to restart. The engine warning lamp will be illuminated and a fault code indicating a ‘cam signal’ problem will be stored. Don’t be tempted to simply renew the cam sensor, as the underlying fault will still be there.
We advise renewing the engine oil and filter at least every 6000 miles/six months (rather than the 12,500 miles/12 months recommended by Mazda). With regular maintenance, these cars can cover well over 100,000 miles without problems.
For a fairly competent mechanic, the timing chain is straightforward to renew, and the required tools are widely and inexpensively available.
IGNITION COIL CONNECTOR PLUG
Our final common fault is misfiring/ rough running of the engine, accompanied by stored fault codes relating to ‘cylinder misfire’. In this case, the problem is almost always due to breakage of the tabs that lock the coil connector plug to the coil, rather than to a failing coil, as so commonly occurs on other cars. The plug then parts company with the coil and electrical contact is lost.
We have seen some very poor repairs to these connectors involving the use of cable ties and silicone. While such methods are OK as a temporary ‘get you home’ measure, a replacement connector is cheap to buy and easily fitted to ensure a proper repair for reliable running.
NOTE: All references in our text and captions to ‘left’ and right’ sides are from the point of view of someone sitting in the car and looking ahead.