Check engine light wire
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Cross-Country
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Check engine light wire
I purchased a used truck but the check engine light never come on even it has emission related codes such as 0420, 0430. I suspect the previous owner removed the wire from the computer to trigger the CEL. I check the wire diagram but couldn't find out where the CEL light was. Can anyone tell me which wire or connector pin that trigger the CEL on.
I want to enable the CEL back on since sometimes there is something wrong the truck but I don't even realize it.
I want to enable the CEL back on since sometimes there is something wrong the truck but I don't even realize it.
Laughing Gas
Joined: Dec 2019
Posts: 893
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From: San Diego, CA
What year truck is it? I have a 2001 Wiring Diagram I can look through, still learning how to use it...
From what I've seen in the past, most people will remove the bulb, or the bulb burns out. Haven't seen anyone cut a wire (yet)...Might be easier to simply remove the dash and check the bulb. At that point you'd probably find the possible cut wire.
From what I've seen in the past, most people will remove the bulb, or the bulb burns out. Haven't seen anyone cut a wire (yet)...Might be easier to simply remove the dash and check the bulb. At that point you'd probably find the possible cut wire.
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Cross-Country
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Mine is 2008. The light is on for a short period of time when I turn on the key so I am pretty sure the bulb is still there. I have the wire diagram as below link but I cannot find MIL light anywhere.
2008 F-250 wire diagram - Ford Truck Enthusiasts Forums (ford-trucks.com)
2008 F-250 wire diagram - Ford Truck Enthusiasts Forums (ford-trucks.com)
Fleet Mechanic
Joined: Oct 2017
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From: Southwest Ohio
If the computer triggers a DTC, the light would come on since you have stated the light illuminates when you turn the key to the on position. Are you certain that those trouble codes are current codes and not historical codes? I'm assuming you're using a scan tool to read these codes?
-- Dave
-- Dave
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Hi ifrythings, I assume the instrument cluster IC receives the signal from PCM through HS CAN bus, decode it and turn on associated lights in the cluster, correct? If so, in order for the MIL light to be on, it needs a power through the light. Where is this light in the diagram? Are the three diodes in message center module switch (pin1) the light for MIL?
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Cross-Country
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If the computer triggers a DTC, the light would come on since you have stated the light illuminates when you turn the key to the on position. Are you certain that those trouble codes are current codes and not historical codes? I'm assuming you're using a scan tool to read these codes?
-- Dave
-- Dave
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Fleet Mechanic
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Hi ifrythings, I assume the instrument cluster IC receives the signal from PCM through HS CAN bus, decode it and turn on associated lights in the cluster, correct? If so, in order for the MIL light to be on, it needs a power through the light. Where is this light in the diagram? Are the three diodes in message center module switch (pin1) the light for MIL?
From the sounds of it, the MIL proves out then turns off, that means the light is good and the PCM is telling the IC to turn the MIL off, if the PCM wasn’t talking to the IC the MIL by default stays on until the IC gets the message from the PCM to turn it off. To me it sounds like the PCM has had something done to it to keep the MIL off.
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The PCM sends several CAN packets that the IC uses and other module’s also, if your tach and speedo are working properly then the PCM and IC are talking correctly. You stated that when you turn on the truck the MIL turns on for a few seconds then turns off right? So it proves out and it works, the MIL is not shown on the diagram as it’s integrated into the IC, the power for it would also be the main power for the cluster pin 1, the message center switches show the 3 LEDs for the back light for the switch.
From the sounds of it, the MIL proves out then turns off, that means the light is good and the PCM is telling the IC to turn the MIL off, if the PCM wasn’t talking to the IC the MIL by default stays on until the IC gets the message from the PCM to turn it off. To me it sounds like the PCM has had something done to it to keep the MIL off.
From the sounds of it, the MIL proves out then turns off, that means the light is good and the PCM is telling the IC to turn the MIL off, if the PCM wasn’t talking to the IC the MIL by default stays on until the IC gets the message from the PCM to turn it off. To me it sounds like the PCM has had something done to it to keep the MIL off.
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murphydo
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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Jun 19, 2001 07:43 PM