Many years ago, when I first started working in the motor industry, we only had to deal with a handful of warning lamps on the instrument panel.

There was low oil pressure, the charge indicator, main beam and indicators, and that was about it.

These days, the instrument panel of the average modern vehicle is littered with a whole host of warning lamps.

Some of these are just for providing information – such as main beam – or to act as indicators, while others are there to warn the driver of possible problems, or even to flag up a major issue.

But how do we know what they all mean?

The first step is to look at the colour of any lamp that lights up in the instrument panel.

This gives us a clue as to its importance and what action, if any, we should take.

Instrument panel warning lamps are colour coded, just like traffic lights: red means stop, and amber means there is a possible problem that might or might not be serious, but could become serious if ignored.

Any other colour means the lamp is just for information.

I frequently see motorhome owners posting on various internet forums that a lamp has lit up on the dash, but everything seems to be fine, so they’ve just carried on – but they would like to know what the problem might be.

This is a very risky strategy, because the problem that has caused the light to come on might actually be causing further damage.

For example, if the engine management light (aka the malfunction indicator lamp, or MIL) comes on, it might be something quite minor, or it might be something that could cause damage to your engine.

Plug it in

It is almost impossible to tell what caused the lamp to light up without plugging in a diagnostic machine of some sort, so asking what might be the cause of the light coming on is a waste of time (although you will get dozens of suggestions from people who have had a similar experience).

To put it simply, if you see a red light on your motorhome’s dash, you should stop, immediately if it’s safe to do so.

Red warning lights mean something is wrong that is likely to cause further damage if ignored, or that is a potential hazard.

Examples would be the low oil pressure light or the low brake fluid light – it is obvious why you should stop immediately if either of these comes on.

Seeing amber?

Amber lights are warnings of faults that might become more serious if not dealt with soon.

These would include things such as ABS or stability control system faults, engine management problems, or a blocked diesel particulate filter (DPF).

If one of these illuminates, you should be safe to go on with your journey (perhaps at reduced speed), but the problem needs sorting out at the earliest opportunity.

Ignoring a DPF warning light, for example, could mean eventually having to replace the DPF, at high cost, rather than getting it cleared relatively cheaply.

Read your handbook

If you don’t know what the dashboard warning lamps mean, start by checking your handbook.

It’s a good idea to read it through and acquaint yourself with what they all represent.

At my garage we’ve seen a number of motorhomes brought in with a bulb failure warning lamp lit, but the owners didn’t know what it meant.

Time to read the manual, people… It will tell you what the light signifies and then you can take appropriate action – that might involve checking your lights, or booking the motorhome in for a diagnostic check.

Look out for the engine light

Engine management lights could mean any one of a dozen or more possible faults, some of which could cause long-term or even terminal engine damage if not dealt with quickly.

This is an amber light, so you are safe to continue your journey, but get it checked as soon as possible.

So what could be wrong? That’s another question often asked on internet forums.

There are at least a dozen or more possible causes for this lamp to light up, ranging from a blocked air filter to a jumped timing belt or chain.

A diagnostic code reader will help to identify the problem, but it is rarely as simple as reading a code to precisely diagnose the fault.

Many possible answers

As an example, a code for the lambda sensor in the exhaust may mean several things.

The lambda sensor measures oxygen content in the exhaust and, from that, the ECU can adjust the fuel injection to maintain the correct mixture control.

It could be that the sensor is faulty, but the air filter might be blocked, causing insufficient air flow.

Alternatively the mass air flow sensor might be faulty, causing the ECU to inject incorrect fuel quantities – that in turn could cause the engine to run hotter or generate more soot, which could then block the DPF.

Modern engines run both crank and cam sensors to enable precise timing of fuel-injection events.

Winter woes

There have been winter instances in Fiat’s 2.3-litre engine of ice forming between the teeth of the cam pulley, causing the belt to jump teeth when the engine is started, which will put the engine light on.

At best this will cause the engine to run poorly, but if the belt has jumped several teeth, it could mean the valves and pistons clash, and cause lots of expensive damage to the engine.

An EGR fault could put the engine light on and, while not immediately a major problem, might cause difficulties later if not fixed.

Some vehicles won’t start, or start but don’t run well, if the EGR valve is stuck open.

Many people bemoan all of the technology in modern vehicles, as it makes it difficult for DIY mechanics to fix things, but overall it has given rise to far greater reliability than ever before.

When we only had a few warning lamps, the average life expectancy of a light-vehicle engine was 60,000-80,000 miles, but nowadays, a life expectancy of 200,000 miles is not uncommon.

A keen motorcaravanner, Practical Motorhome’s technical expert Diamond Dave runs his own leisure vehicle workshop. Find out more at Dave Newell Leisure Vehicle Services.