Can the "Check Engine Light" be disconnected?

I have purposely disconnected a few sensors to see if the Check Engine Light is working and no luck. It lights up when the key is turned on but how is it connected to the PCM? I bought the Windstar 1 month ago from a dealer who carries a 6 month warranty on thier used vehicles, and if there are codes I am not being notified of, I want to know so they could potentially be covered under warranty. This came up on a thread I posted yesterday with what appears as though my IMRC is not working, 1 lever is open and 1 closed at all times, but the Check Engine Light is not on.

Hi
no expert here but I think the short answer is no. The PCM as you realize monitors so many things and has the capacity to trigger many, many trouble codes and turn on the light. I once wanted to purposely trip an O2 sensor code, so I disconnected one of the O2 sensors. I was amazed at how long I had to drive around before the check engine light came on. Point being, it can take patience. I would think however that if you disconnected something that is "more critical" early in an engine cycle, say the throttle position sensor, IAC or coolant temp sensor, you should trip a code pretty quickly.

Let us know how it goes. BTW, do you have an OBDII scanner? If not, pull into an Autozone or similar and ask them to scan the van. You would then know if there were codes, but no light.

Good luck

Thanks for the feedback busboy4. That's the answer I was looking for. I would be PO'd if the previous owner were to somehow disconnect the Check Engine Light. I will need to do some more verification to see if the IMRC is actually faulty. I did disconnect it, so I'll see if a code comes up within the next couple days.

I did scan the PCM with my Innova 3100 OBDII scanner and no codes were seen. The repair shop quoted me $50 for a scan so i figured it would be a good investment. I know thiers are more advanced, can they detect codes even before the PCM turns the CEL on?

Hi
Not sure about the capabilities of Pro scanning equipment, but I will say that having an OBD scanner has made my life so much easier. I can check out what the light is telling me anytime and most importantly reset it.

As to your IMRC's, search the forum as there have been numerous threads regarding their function and repair.

Thanks for the feedback busboy4. That's the answer I was looking for. I would be PO'd if the previous owner were to somehow disconnect the Check Engine Light. I will need to do some more verification to see if the IMRC is actually faulty. I did disconnect it, so I'll see if a code comes up within the next couple days.

I did scan the PCM with my Innova 3100 OBDII scanner and no codes were seen. The repair shop quoted me $50 for a scan so i figured it would be a good investment. I know thiers are more advanced, can they detect codes even before the PCM turns the CEL on?

When the PCM detects a fault (except for misfires) it stores the code as a pending code but doe not turn on the CEL. If it "sees" the same fault code within 20 drive cycles it will then turn on the CEL. Similarily if it does not see the fault it will eventually purge out the codes. This is to protect against glitches.

Your 3100 does detect pending codes. (I have the same model).

If you want to check the operation of the CEL there is a built in test. When you start the vehicle the light should illuminate for a few seconds after the engine is started and then turn off. In some areas this function is tested prior to emissions testing.

If you purposely introduce a fault it will take some time to illuminate the CEL. You will need 2 drive cyles (within 20) with the fault. This is not necessarilly two trips but rather it must be 2 OBD drive cylces. (An ODB drive cycle is described in the owner's manual.