Why is the check engine light persistent

Thursday February 27 2020


By Paul Kaganzi

Hello Paul, my Toyota Kluger shows a check engine light. The mechanic ran a computer diagnosis and said the engine communication faults were caused by loose battery terminals. They tightened the terminals but the check engine light fault is back. What can I do? Alice

Hello Alice, you may need a second opinion. Whereas the loose battery terminals will cause communication faults on your Toyota, it may not be the cause of the check engine fault light.

The check engine light displays when your engine has a fault with the car emission control system. This is any component that affects the quality of exhaust emission or complete combustion of fuel air mixture.

This can include the engine management computer, ignition system (bad spark plugs or coils), fuel supply system (weak pump, dirty filter or deposit blocked injectors), air intake system (dirty air cleaner, leaking intake tunnel or deposit clogged throttle unit), leaking vacuum system or exhaust system (damaged catalytic convertors and oxygen sensors).

Correct analysis or diagnostic routine should help the technician determine which of the above areas has caused the check engine light display. An emission system fault causes poor fuel economy and reduced engine performance.

What is the difference between the car differential lock and 4WD?


Hello Paul, Can you help me understand what the differential lock is on a 4WD vehicle and what is the difference with four wheel drive? Chemonges

Hello Chemonges, to understand what a differential system is on a four wheel drive (4WD) vehicle you need to appreciate that car wheels move at different speeds which helps them turn through corners efficiently because the wheel closer to the corner will rotate at a different speed from the outer wheel. There are tricky situations on a road such as a slippery section or patch, uneven terrain with gulleys where a wheel will not have contact with the road.

This is when you need the differential lock which when engaged will direct power to the wheel that is easiest to rotate because it has traction. The locked differential enables the two wheels to move together and get the vehicle out of the tricky situation. The differential lock facility is fitted on a vehicle’s front and rear axles.

This feature locks the side shafts of each axle in order to distribute power on a 50/50 ratio between both wheels on the same axle (front or rear) to help them move at the same speed. On the other hand, 4WD locks the front and rear propeller shafts in order to distribute power between the front and rear axles on a 50/50 basis.