The check engine lamp on my '94 Camry V6 as come on and gone off twice recently. I thought once a check engine lamp came on it stayed on until something was done. Does anybody know what this on-off behavior suggests?
-- jim
If the check engine light is illuminated, it means that the electronic control unit (ECU) has detected a problem. If the check engine light is flashing, it means that the ECU has detected a serious problem and you need to stop driving and/or take it to a dealer ASAP before serious damage is done to the engine.
In some cases, there is 2-trip detection logic for the check engine light to come on. In other words, a condition has to be present during 2 trip cycles for the light to come on. If the problem is marginal or intermittent, the ECU might not detect a problem and then turn off the light until it detects the problem during 2 trips again. In this case, there is usually a trouble code stored in the ECU.
Ray, you should start a website called "whattodoaboutyourOBDIIcheckenginelight.com"
LOL! Automakers should print it on the front cover of the owner's manual too!
BTW, is a 94 Camry OBD II or previous generation?
Thanks very much for your reply.
If I understand what you said the lamp coming on and then going out indicates the problem happened on two successive trips, but did not repeat on some later trip. So, the sequence goes like this:
The problem is detected. The ignition key is turned off. The car is started again. The problem is detected again. The lamp comes on. The ignition key is turned off. The lamp comes on every trip as long as the problem is detected. This could be many trips. There is a trip where the problem is not detected. The ignition key is turned off. The car is started again -- this time the lamp does not come on.
Then the cycle is repeated again the next time the problem is detected twice in succession.
-- jim
Basically, that's it, except that a "trip" is not necessarily just an on-off of the ignition. There are parameters that define a trip, i.e., cold start with coolant temp below a certain point, then engine and coolant warming up to a different specified point, emissions system going into closed loop, traveling a certain distance, etc.
Some codes have a 1 trip detection logic also. At this time don't worry about when it comes on but why did it come on... get the codes read and report back to us.
You know, I can't remember for sure, but I want to say that the camry went OBDII one year ahead, in '95. I would expect this guys camry to be the old under-hood terminal jump deal, but I might be wrong.
It's not the new universal type.
-- jim
Let us know how it turns out.
OK, the light came back and stayed so I had my favorite mechanic do the code check. He specializes in Toyotas (Bob's Toyota), but isn't a dealer mechanic. He said the light was pointing to an oxygen sensor, and that he'd had a rash of Toyotas come in with this indication since they began putting ethanol in the gasoline in our area. He thinks ethanol is causing the oxygen sensor check engine warnings.
-- jim
Alas the poor O2 sensor, the most changed good part on the modern automobile. A contaminated O2 sensor is most often the RESULT of some other fault that is not allowing the microprocessor to control the fuel/air ratio within it design parameters and activating the check engine light. If anything the ethanol is probably just burning off some carbon deposits on a twelve year old car. It could be as simple as a bad plug or wire. If not look for a fuel metering or spark control problem, WBMA
mike hunt
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