Check Engine Light - Bulb Out or Tampering?

#1

I am looking at replacing my very old Dodge Caravan with a less very old one. I am currently looking at a 2003 Grand Caravan, 3.3L engine, 108K.



Other than the fact that it probably needs ball joints it runs great, drives & handles great.



One problem, when I turn the key to that spot where all of the indicator lights come on they all seem to work EXCEPT the Check Engine Light.



I know that no one can say for sure what the story is in this case, but is it possible to tamper with/disable the OBDII? And other than pulling the instrument cluster and replacing the bulb (or whatever it would be) is there some way to find out? The manual doesn’t identify any kind of a fuse or relay. Is there likely to be one?



I do plan to run it by an AP store to have them hook it up to a reader and see what they get, but if they get nothing I still won’t be sure what that means.



If I didn’t generally like the van so much I would just run for the hills.



Any tricks? Advice on sorting it out?



Thanks.

#2

You’re on the right track wanting to get it checked for codes. If there is any tampering, it would probably be along the lines of bulb removal. Or else it stayed on so much that it just burned out…

#3

Absolutely agree with stronzo. That is a red flag simply because the Check Engine Light just doesn’t burn out all that often.

#4

If you live in a area that not require emissions testing, the CEL is not that big a deal…If the vehicle will need an emissions test at some point, have the present owner get one NOW. This will force the issue as they usually check CEL function as part of the test. If the owner says “it doesn’t need one now” just tell him if he wants to sell it to you it does…

#5

pull codes they have a code for the bulb on that model.

good luck

#6

Thanks for all of the feedback. The seller did let me take it home overnight, so I’ll be swinging through an AP store in the morning to have codes pulled.

So far it seems that the idea is that the bulb might be out and if there is anything “shady” going on it might just be that the seller knows but isn’t saying anything.

Any other “shadier” possibilities?

#7

Of course, if the bulb’s burnt out that might mean they’ve been driving around with the check engine light on forever.

#8

The bulb could be burned out and I suppose there could be a faulty connection to it in the socket. Hopefully it is one of those two things. If the bulb is missing then that is a warning sign. There could also be a problem with the bulb circuit in the BCM module. If that was the case you would have to replace the module and that is a lot of money. Before you purchase the van be sure you find out what is causing the trouble. You also want that light to work so you have a warning when the system detects trouble.

#9

also… here in Mass when you go for an auto inspection they hook up the car to the obdii reader. if they are doing just the safety inspection and they’re no codes they pass the car, but if there are codes or errors, they won’t. hopefully your state doesnt use the code reader. you shouldn’t buy this until, unless you find out why the bulb is off.

it sounds fishy that the bulb doesn’t come on during the key on stroke of the ignition.

#10

FYI: so I finally figured out that, though the bulb seems to be out of order, this vehicle does apparently “ding” at you when it sets the light. (It dings about 10 secs after startup. Its an unfamiliar vehicle so it took me a while to catch on).

I had codes pulled and the only thing in there was P0442 (small evap leak). Unless it is just a bad gas cap these do tend to be really annoying and pesky problems, but really not a big deal. I think I’m going to assume that the OBDII system is fine (though I wonder why it wouldn’t throw a code for the bulb since some have said that there is one); that the van has an evap leak; and that the light was probably on for a long time with someone who didn’t want to bother with it and had mechanics & others saying it was no big deal. The last is the biggest guess, but I can’t verify it b/c the seller is not original owner and is c-l-u-e-l-e-s-s.

Thanks again to everyone for the feedback.

#11

The CEL light should be on when any code is set. It also should be on when the key is turned to the RUN position to test the dash warning lights. While it is good that you don’t have any serious codes active you are not out of the woods yet. You need to see why the light isn’t turning on. If it is because the circuit to it is bad in the BCM, that will be an expensive item to replace (many hundreds of dollars), especially for just a nonworking light. That light is important to have working. At least though you have an audible alarm to tell you something is amiss. As was pointed out already, in some states that do vehicle testing, if that light doesn’t work the test is stopped right then.

#12

Did the tachometer indicates rpm? The PCI Bus line, on a white/violet wire, goes from terminal 59 on the engine computer (PCM), to the instrument panel PCI Bus, where it (I presume) goes to both the tachometer gauge and the check engine light (MIL lamp).
If the white / violet wire connection is broken between the PCM and the instrument panel; both, the tachometer and the check engine light won’t work. Then, it may be as simple as following the white / violet wire and repairing it.

#13

All of the dash lights light up in the RUN position, except for the CEL. Given the audible alarm and the presence of this code, I am currently going on the assumption that the system is fine - except for the bulb.

What kind of “test” am I asking a shop for if the question is about whether I have a malfunctioning computer or just a bad bulb?

In my area I don’t have to worry about it for inspection.

#14

Ask the service shop to check out why the CEL light isn’t working. They will check and see what is going on with it.

I earlier stated that the light may be tied to the BCM module but thanks to Hellokit’s info it looks like it ties to the PCM under the hood and that really makes more sense since it is for the engine systems. Also as he pointed out, the light isn’t controlled by just a simple ground connection through the PCM as I had thought, but uses a communications BUS line. This could mean that the problem may be with the cluster side of the circuit, that the light is in.

The dealer service department will have what is called a DRB box that communicates with the vehicle computers. You may be wise to have the dealer service department look into this since they will have the proper diagnositc tools to work on this problem.

#15

My earlier reply to hellokit seems to have gone to nowhere…

I had to return the van this morning, so I can’t check the wire. But the tach does work normally. Even so, if/when I look at the van again I’ll give that wire some attention - thanks for that.

Is it only a dealer that can verify the computer function? The shop I usually use if pretty up to date with everything. Will the dealer have things (like this DRB box) that my shop can’t replicate? (I just try to avoid dealers).

#16

Since you live in an area where you aren’t subject to emissions tests, the van could be a good buy for you. The check engine light being out, and the EVAP code being set, have NO effect on how the engine runs. I feel that the evap standards, and controls, are overly demanding and strict. Of course, I don’t count.
If you HAD to repair the EVAP problem, and the check engine light, it could be very expensive.
You want the check engine light to come on when there are problems. If you don’t have it, you will need to scan the engine computer for any codes, every so often.
Maybe, my reference is wrong: http://www.etools.org/files/public/generic-protocols-02-17-03.htm It shows Chrysler (Dodge) as beginning to change to CAN protocol in model year 2004. The point is, that one wire carries information to several components. If they were all out, they would have a common cause (one interrupted circuit, or wire)
It’s, maybe, just the lamp bulb burned out; which could be fun to replace.

#17

The shop you use may have something that will do basically all the things that the DRB box can do but may not be able to all the things. You would have to ask them about that. I just think that the dealer is usually better setup to work on some specific things, like this kind of thing (PCM BUS communications), than most independent shops at least.