Check engine light on, no codes stored

My wife and I recently bought a 2003 Pontiac Vibe, a Toyota Matrix with slightly different skin, and shortly after we got a check engine light. When I inspected the car before purchase I noticed that there was black soot in the exhaust pipe. The owner told me that he’d put a cat back exhaust but I suspected I’d probably be replacing the O2 sensors soon and we negotiated the price accordingly. So now it’s a month later and I bought an OBD II checker. I followed the instructions and after the checker and the cars ECU linked it showed no stored codes. I turned off the CEL and we went shopping. Mid way on the drive home, we live out in the country, the CEL came on again. Went through the procedure again, still no codes stored. I’ve read the instruction manual twice and I don’t think I’m doing anything wrong. Is it possible to have a check engine light on and there to be no codes stored for the OBD tester to find? I could have bought many rolls of black tape for what the tester cost and I kept the receipt just in case.

I’ve never heard of it, but apparently it’s possible… {:slight_smile:

I commend you for checking the car out thoroughly before buying, but soot on the tailpipe of a 12 year old vehicle would not bother me unless it were extreme, like creeping up the paint. All aged engines put out some level of soot, even if miniscule, and it can build up over the years. You were absolutely smart to negotiate a new catback system because of it, however. It builds up on O2 sensors and converter catalyst too.

My recommendation would be to get it checked at a reputable independently owned and operated shop. It’ll probably run about a hundred bucks (one hour shop time, often a minimum charge), but their equipment is generally much better than the average homeowner’s.

Let us know how you make out. We do care.

My experience has shown that anytime a Check Engine light comes on, and there’s no codes stored, there’s problem with the computer.

Let’s face it, the computer is an emission control device and shouldn’t do that.

I’ve seen computers fail in all kinds of ways.

Besides your description, the Check Light turns on, and there’s ten different codes stored for different systems. Or, that as long as the Check Engine light is on the engine runs. But soon as the Check Engine light shuts off the engine shuts down.


I see things a little differently . . .

OP isn’t seeing any fault codes because his code reader simply isn’t good enough to retrieve the fault codes

Most likely the fault code is a manufacturer-specific code, and OP’s tool is simply not good enough and can’t retrieve it

The fact that OP was able to extinguish the light, implies . . . to me, anyways . . . that there was a fault code

This may very well be a situation where OP’s code reader can’t display and/or retrieve the manufacturer’s fault code, but is able to clear all codes in the PCM, thus extinguishing the mil

I think @db4690 is right, the codes are stored, just something about the code-reading equipment that the OP is using, for some reason it isn’t showing the codes. Less likely, but still possible, the ECM isn’t properly communicating with the code reader b/c there’s something wrong w/the ECM.

Even less likely, ok, this one is admittedly off-beat and not very likely at all. But something to consider. Did this purchase require an emissions test by the DMV? If so, I’m wondering if somehow the seller knew it wouldn’t pass, so has disabled the ability for the ECM to store codes. That would work, b/c they could turn off the CEL, and since no codes were stored, the emissions testing station wouldn’t realize the CEL had been turned off just prior.

The codes are there it’s a code reader issue, Actron is one I know has difficulty with Toyota. Find a shop or someone with a higher end scanner to read your codes and go from there.