Check Engine Light Not working?

[ndsti]

Okay, before you critize hear me out. I have done a search and came up with nothing. Here's my problem, my check engine light does not work. i have tested the bulb and the contitunity on the back of the circuit board, everything checks out ok. I have and OBD II reader and can tell when the car throws a code, my codes are as follows i have got p0302, p0300, and another one that tells me the IAC is malfunctioning, I got that one fixed though. I know what the codes are. When the PCM throws a CEL the light does not come on. I have changed the spark plugs and wires nothing else yet. if you need more information just ask. any help would be greatly appriciated

 

[talon212]

If you can pull codes but you don't get a (CEL) then check the bulb inside your cluster. My gas light went out and it was the bulb. I found that out after I replace my fuel sending unit.

 

[luv2rallye]

First check it's fuse. If not that then check if a wire is broken, foil path broken, or a connector pin is not making good contact. You need to check continuity from the ECU (PCM?) to that bulbs connection contact (ECU provides the ground). Since you haven't filled out your vehicle profile I can't tell you any specifics as they are different on various years/models.

 

[ndsti]

Thanks guys for the help so far. I have checked the bulb and it's good. My car is a 98 GSX no mods to the ecu. I have been told that the ecu is in the middle of my car close to the firewall under my radio is this correct? What wire would i have to ckeck or pin #?

 

[luv2rallye]

Yes that is where it is. CEL is on pin 36 of ECU (green/red wire) on a 16 pin connector (B-54). If you ground it the CEL should light with key to "ON" (pull connector to be ECU safe although if you can't, it should also work and be ok).

 

[ndsti]

thanks. okay i'll try that this weekend since my cruise light burnt out...that gives me a good reason. thanks

 

[wret]

Please update your profile with your current vehicle info. Thanks.

 

[ndsti]

their you go..thanks for the help guys.. I appriciate it

 

[dieseltech]

The story on codes. OBD II is a wonderful thing. codes P0300 (multiple misfire detected) and P0302 (misfire cylinder #2) are universal codes. That means every OBD II vehicle has the same diagnostic for those codes. Your CEL only comes on when those codes are active. They will flash at the time of the misfire, it may be so quick that you don't even notice it. DTC's that flash mean they can harm your engine. Then there are the codes that keep your light on, these codes mean that your engine is putting out more than the allowed amount of emissions for that model year vehicle. I'm sure there is a better explaination of OBD II codes, but I'm in a hurry because I need to go to the bathroom.

I was also going to state weather or not your CEL illuminates when you first turn the key on and then goes off. This is called a buld check. The bulb check allows a person to see all "Idiot lights" being illuminated. Most people don't care to look at their bulbs in this time, however, it is very important. If your CEL does illuminate when you first turn your key on, then it is operating properly and needs no diagnosis.

 

[akdsmer]

The story on codes. OBD II is a wonderful thing. codes P0300 (multiple misfire detected) and P0302 (misfire cylinder #2) are universal codes. That means every OBD II vehicle has the same diagnostic for those codes. Your CEL only comes on when those codes are active. They will flash at the time of the misfire, it may be so quick that you don't even notice it. DTC's that flash mean they can harm your engine. Then there are the codes that keep your light on, these codes mean that your engine is putting out more than the allowed amount of emissions for that model year vehicle. I'm sure there is a better explaination of OBD II codes, but I'm in a hurry because I need to go to the bathroom.

I just went to the bathroom, so let me clarify:

If your MIL (check engine light) flashes, then there is a current, potentially catalyst damaging misfire occuring. If you have a non-catalyst damaging misfire (small misfire) then the MIL will illuminate and the code for the offending cylinder will be stored. If the misfire cannot be linked to a particular cylinder, then P0300 code will be stored. The MIL can stay illuminated even when the codes are not "active". Ie, a P300 code for RANDOM misfire could be stored even when the misfire is not occuring. Keep in mind that codes aren't always correct- for example a P0340 camshaft code can be caused by a bad crank sensor.

I wouldn't pull the PCM connector loose, just see if there is 12V at the wire. If there is, then you have a computer that will not provide the necessary ground, but the rest of the circuit is good. Then apply a ground to that wire and the bulb will then illuminate. If that works, then it is either a bad PCM or you have a bad PCM ground. It is not all that uncommon for bad PCM drivers (what grounds the light circuit) especially if the MIL bulb has been replaced with an incorrect bulb, that allows too too much current through the PCM driver. I would verify that the MIL bulb is correct to prevent any future problems!

 

[ndsti]

Thank you for the explaination. My reader tells me if the light has been tripped on and to the other question concerning the idiot light, no it does not come on when key is turned. Therfore i cannot tell if it is flashing. I'll check the wire from the PCM to the light this weekend. Thanks

 

[ndsti]

You won't guess what i found after hunting through the PCM wires. The guy that had the car before me cut the wire so that i wouldn't know about it. Bastard

 

[dieseltech]

wow, that's pretty low of him.