BACKYARD MECHANIC: Traction control light indicates problem

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This article was published 30/07/2010 (5574 days ago), so information in it may no longer be current.

QUESTION: I am hoping you can shed some light on a problem I have had for some time now.

I own a 2003 Land Rover Discovery SE, which I purchased new in 2004. From Day 1 I have been having an intermittent problem with the traction control indicator light coming on in the instrument panel. The TC is not actually engaging, as when it does it makes a very distinctive noise.

There seems to be no rhyme or reason to it coming on; the truck is warmed up, or upon start-up; driving down the highway at 100km/h on a sunny summer day or parked in my driveway motionless. I have been using the same mechanic at the dealership over the years and he is as baffled as I am. He tells me he has replaced virtually every piece of equipment that could be the culprit, from ABS sensors to wiring harnesses, yet it persists. I know British vehicles are legendary for their electrical issues, but it’s irritating. I am hopeful you have some suggestions or knowledge to share.

ANSWER: The traction control light should come on for about two seconds every time a traction control event occurs, but as you state, you would also hear the system working. As it also comes on sometimes when the vehicle is stopped, it is safe to assume that the light isn’t coming on because of a traction control event. It can also be assumed that the wheel speed sensors are OK because this would turn on the ABS warning light. The traction control lamp is operated by the ABS/Self Leveling computer when it applies a ground internally for the dash warning lamp. Any fault in the system that would turn on the traction control lamp should also set a trouble code. As your mechanic hasn’t been able to follow that route, I would think that either the problem is something that doesn’t set a trouble code or the problem is in the ABS control computer itself.

The lamp should come on if the traction control system is disabled, such as manually turning it off, so I would look for problems starting at the manual control switch for traction control, hill descent control and the related wiring. An intermittent short to ground on any of these could turn the system on and off. If everything there looks good, the problem is likely in the ABS control computer. Good luck!

QUESTION: I have a 95 Toyota Camry 2.2- to 4-cylinder and there is an engine noise when you first start it. Could it be the timing belt? I would appreciate your suggestion.

ANSWER: A timing belt can make a "singing" noise or high-pitched whine if it is installed too tight but other than that, it operates quietly. There are several other items that can make noise just at start-up — some are costly to repair while others can be fixed relatively cheaply.

First, make sure the noise is coming from the engine rather than an accessory such as a power steering pump or alternator bearing. Remove the drive belt and operate the engine for a few seconds. If the noise is still there, it is probably in the engine, although transmissions can also make noise. A ticking noise could come from the valve train. Your car has manually adjusted valves and the clearance may need to be set. Once the engine warms up and parts expand, the clearances become less so the noise seems to disappear.

A knocking or heavy sound from the engine could be caused by excessive piston clearance or worn bearings. The noise will become quieter as oil pressure rises and engine temperature increases, but both of these noises are costly to repair.

This engine also has gear driven balance shafts beneath the crankshaft and clearance in the gears can make a rattle sound until oil coats the gears. The gear clearance can be adjusted but this noise isn’t a problem as long as it disappears immediately after startup.

There are a lot of items that can make a noise, so I would recommend you take the car to an experienced mechanic. You will have to leave the car for a day or two so it can be started cold, but a good mechanic can narrow down the noise and suggest repairs if needed.

Jim Kerr is an experienced mechanic, instructor and member of the Automobile Journalists’ Association of Canada.

kerr.jim@sasktel.net