CHECK ENGINE LIGHT?
Take a look at some of the most common causes and learn how you can address them inexpensively
More than almost any other vehicle problem or symptom, checkengine lights (CELs) can cause anxiety in drivers. Once a vehicle is out of warranty, taking it into the shop to have a check-engine light diagnosed and repaired is like leaving a blank cheque on the service counter.
Automakers jam more and more computers into our vehicles every model year, but often they still provide only a single warning light for most diagnostic trouble codes. These codes can come from transmission faults, engine control failures, emission problems, and the list goes on. But just as vehicles have evolved, so have the quality and volume of DIY tool suppliers and websites dedicated to taking some of the mystery out of this ominous little light.
A good example is CarMD, a California company that markets and sells a diagnostic reader. While many companies offer code readers, CarMD product purchasers also get access to a large database of easy-to-understand technical information that can provide not only the most common cause for almost any fault, but the average cost of repairs.
CarMD collects information from their products’ users and other sources to compile various reports, such as the vehicle brands with the lowest (and highest) number of check-engine light related problems and those that are the most expensive (and cheapest) to repair.
Here is a portion of CarMD’s top
check-engine-light causes for 2016 and some ways to cope with them inexpensively:
Replace thermostat: All injected engines monitor coolant temperature and their on-board computers will flash the CEL if the engine fails to reach full operating temperature within a specified time, distance, and engine load/speed after startup. Even most auto novices would expect that the engine’s thermostat is the likely cause and they’d be correct, but it’s not always that way. A faulty coolant temperature sensor or wiring may provide a false signal to the computer, or extreme ambient temperatures, combined with short stop-and-start runs can also be a cause.
If you use a code reader and this fault comes up with no other related cooling-system symptoms (such as little or no heat in the cabin, or a temperature gauge out of whack), try leaving it for a few days, especially if the winter temperatures are low, before taking it in for an inspection. But be warned, the computer uses coolant-temperature signals to adjust fuel mixture and if it thinks your engine is running too cold, your economy may take a dip and you risk related problems from letting too much fuel run through your auto’s emissions system.
Tighten or replace fuel cap: According to CarMD, this was the No. 1 CEL cause in 2014, but it has steadily dropped since then. It shows up on a scanner as a “large evaporative system leak.” Often it’s caused by a driver forgetting to properly tighten the gas cap after
refuelling, but on older vehicles it can be the result of a worn cap seal or rust on the fuel filler neck. Keep in mind that if the cause was a loose cap, after tightening, it can take one or two days of driving until the computer clears the fault and extinguishes the CEL. The good news is that this is the cheapest CEL to rectify and, according to CarMD, the average cost of this repair last year was a mere US$15.31. Replace ignition coil(s) and spark
plug(s): This fault shows up as a misfire code on diagnostic displays and most vehicles have the capability of narrowing it down to a specific or multiple cylinders. As many autos run long-life platinum spark plugs, these CELs usually don’t show up in lower mileage units. Most modern vehicles use individual ignition coils to fire the spark plugs, and their protective boots can exhibit dry-cracking with age, leading to arcing (electricity grounding outside of its normal path), thus reducing the power getting to the plug. Check your owner’s manual for spark plug replacement intervals. If your ride is due, having a new set of plugs installed is a good idea.
If you’ve had your ignition system checked and updated with new plugs (and coils if needed) and the CEL is still on because of a misfire code, there may be an air leak allowing too much air into the system. An incorrect air/fuel mix can trigger a misfire code just as quickly as a bad spark plug. The average repair cost for this code was US$390 last year.