Check Engine Light


This condition activated the Check Engine Light while driving down the mountain from Sequoia.

It seems that I have one more thing to milk tell about my recent 3 day trip, and this may help you in the near – or distant – future.

Despite taking obvious preventative measures, when you have a car that is 23 years old….things can happen. That is, unless one is willing to replace every electronic or moving component in the car. Even then, brand new cars have been known to break down on the road. Because while the engineers know what MTBF (Mean Time Between Failure) each component may have, there are statistical deviations between the norm.

I have mentioned a late friend from time to time, Bob Sanigar. He was what I would call a classic master mechanic who apprenticed in 1950s London – having worked on everything from Ferraris to VWs. And we had an interesting conversation one evening – should one replace some components based on the fact that they are old and have miles – or wait until they fail? 

Bob had an interesting answer – just because you put a new component in the car, doesn’t mean it won’t fail soon.

Had that happen to me once when I replaced a perfectly good old O2 sensor (that tells the fuel injection system how much to lean or enrichen the fuel for the catalytic converter) with a new one.

The new Bosch sensor was completely dead. Right from the box. The old one still worked fine.

Which isn’t to say, in my opinion, you shouldn’t change anything until it breaks. Obviously changing a water pump – it you have to take it off anyway to access something else – with 200,000 miles is probably a smart move. For the price of the part – and no additional labor – you have (probable) piece of mind. I’m talking about a perfectly quiet functional old pump – with no bearing noise indicating wear. If there is noise, that is a warning to change it.

Anyway, I am starting to get sidetracked here.

1996 was a seminal year for US autos

The manufacturers had to implement the government mandated standards utilizing OBD IIOnboard Diagnostic System.

Cars truly became computer oriented. Whereas before the ignition system consisted of a distributor with a rotor that fed power to each cylinder as it rotated (and had a weight to make it advance as the RPM increased – since you have to start the burn process of the air/fuel mixture earlier as the pistons moved faster)  – now each cylinder had an ignition coil, which would fire on a signal from the computer. Instead of a crude weight which made the ignition advance, the computer, with the aid of knock sensors – devices that can sense the impending predetonation, or “pinging” and back off the timing ever-so-slightly, and extract every bit of power that fuel can deliver.

Instead of the whole car being immobilized if the old distributor had a problem, the computer will sense a failure in one of the cylinder’s ignition coils with the car still able to function until you can get it repaired.

But you have to know what is wrong. And more importantly, just because you have a check engine light on doesn’t necessarily mean the car will immediately self destruct.

Had the light come on 2 years ago while driving the Oregon Coast. After thinking “oh !@#”, I stopped and got an inexpensive OBD II reader. Should the car be immediately towed to Eugene or Salem or could I “press on regardless”?

The reader is easy to use – regardless of make. All cars 1996 and later will have a port under the dash – near the steering column, where you plug in the reader. Turn the ignition on (not the engine) – just so the dash lights are on – and it will eventually – after 20-30 seconds – tell you the code.

The reader gave a code for a cylinder misfire – #7 cylinder. The V8 did have a slight roughness when it was idling. I like getting factory or OEM (Original Equipment Manufacturer) parts and finding a new factory igniter for a (then) 21 year old car was probably impossible on the Oregon Coast.

Even a  dealer in Salem or Eugene would probably have had to order one with a day or 3 wait.

And getting an off-brand unit at a chain parts store on the coast would have probably involved a wait.

So I decided to drive the remaining 500 miles on 7 cylinders.

If you have a 4 cylinder engine with this condition the car might be undrivable and you would have to wait. Three cylinders firing out of four would be a lot rougher and noticeable than seven out of eight.

My only concern was the fuel injection system still spraying fuel into a cylinder not firing. Raw fuel running down the cylinder wall and washing away oil could score the walls and give you a serious and very expensive problem. I was hoping that the computer was smart enough to direct the fuel injection system to stop spraying fuel in that cylinder.

I took the risk.

When I got home, I found out from my shop friend that the computer was smart enough (at least on the old Mercedes) to shut off the fuel in that condition. When a second coil failed a month or so later, I just replaced all the remaining 7. Gave me the confidence to make other long trips. Which I have done.

So anyway, I’m coming down the mountain and the check engine light comes on. I do a quick scan of the coolant temperature (fine) and oil pressure (fine). The car isn’t making any strange or ugly noises.

It’s probably safe to drive to the nearest town where I will have lunch and pull out my reader to see what is wrong.

Most modern cars have variable valve timing, which which gives you the best of both worlds. Which is low end drivability and economy and high speed power.

Used to be when you were at a stop light in the 60s or 70s and a car came up with this idle

You knew it was a hot machine. It had what hot rodders might call a “radical camshaft” – that allowed more air and fuel into the cylinders for more power. They weren’t helpful at lower (< 2,000-3,000) RPM, but once you got going….

VVT allows the best of both worlds.

My reader was telling me that on the right bank of the V8 engine, the component that controls the camshaft timing was giving trouble.

Which told me that the car was at least drivable. I used the reader to erase the code in the memory and it hasn’t come back on since.

A call to my friend who has a Mercedes shop said that sometimes the oil viscosity – or not changing  it enough – can trigger it. Neither was the case, although I used a Mobil 1 5w-40 which on a hot Central Valley day can give a reading of “almost” 0 pressure at idle.

In any event unless the problem keeps returning I’m not going to worry about it.

In some years and models, a check engine light can be triggered by a loose gas cap. And what can be vexing, one can tighten the cap and the light won’t go out. Making one think that the problem wasn’t the cap.

That’s because the government mandated that so many start-stop cycles must be done to “prove” to the computer that there is no longer a vacuum leak.

With a reader, you can reset the code, which will turn off the light.

The difference between the inexpensive readers (~$20) and the more expensive ones ($100 and up) is that the more expensive readers can show you the proprietary auto manufacturer codes. In my case, the unit asked for my car make and P1519 is apparently a Mercedes specific code. Probably a Mercedes code for a Mercedes V8 or V6, as it knew which side of the v8 was giving the problem.

There are also government mandated generic codes, such as an O2 sensor bad,  common across car makes.

Even if your reader wouldn’t tell you what a “P1519” code is, a search engine with your make on the Net probably would.

You have to wonder how many trips were ruined for people when the light came on and all it was was a loose gas cap.

You don’t even have to know a lot about mechanics to benefit from a reader. When in doubt, call your shop with the code. Under no circumstances should a check engine light be ignored but with a little knowledge you can decide whether to stop and attend to it immediately or finish the trip.

I wouldn’t have been happy missing the beautiful drive of CA-1!

1 Comment

Filed under Car Pr0n, Other Stuff, Small Stuff, Travel

One response to “Check Engine Light

  1. Pingback: Maybe A Neuroscientist Can Explain It | The Lexicans

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