One of my inspection 'fail' items was no check engine light (key in run position, engine off). Last weekend I took out the cluster, replaced all 6 illumination bulbs and the check engine bulb. I couldn't see any broken filament, so I used a 9V battery & a couple test leads to make sure the bulb was actually dead. Confirmed: old bulb was dead, new bulb was good. So that was a sigh of relief - easy fix! I put it back together, took it for a test drive around the block, tried it again a couple times & CEL came on & back off again - no problem.
Fast forward to Monday - check engine light comes on & off normally. Drive to work, shut off truck, try again - no CEL light. Check again a couple hours later, CEL light. Drive home, no light. Tuesday morning, light but no light since then.
Although unlikely, I know it COULD be a bad bulb, so that's probably the cheapest/easiest place to start. I'm in Maine, so I know hot-cold-hot-cold can affect electrical connections, and probably has something to do with it. When I did the replacement I looked at the contact brushes between the bulb receptacle & the board connection. They looked 'ok' I guess - slightly indented where they've been pushing down all these years, but ok, and I bent the copper down a teeny bit to be sure there was good contact. But I suppose I could reseat the connector and double-check the contacts. (BTW, all other lights are fine, so if it's the PCB it's only that branch circuit.)
I guess my question is this: besides these couple low-hanging fruits, does anyone know of other reasons that this might happen with just the one bulb? Is there a common failure that manifests with this symptom?
Follow up: during the inspection, he plugged in the OBD & said there was a code stored (the P1401 DPFE code, I think). After the CEL bulb was working the light was never came on after starting the engine. Of course the battery was disconnected while I did the work. So does unplugging the battery CLEAR a code or does the CEL just not come back on until it's triggered AGAIN. Also - I vaguely think an inspector once told me that one code stored was OK, but 2 was a fail. That seems like bunk to me, but it's part of why I ask the question.
Thanks!
Todd
Fast forward to Monday - check engine light comes on & off normally. Drive to work, shut off truck, try again - no CEL light. Check again a couple hours later, CEL light. Drive home, no light. Tuesday morning, light but no light since then.
Although unlikely, I know it COULD be a bad bulb, so that's probably the cheapest/easiest place to start. I'm in Maine, so I know hot-cold-hot-cold can affect electrical connections, and probably has something to do with it. When I did the replacement I looked at the contact brushes between the bulb receptacle & the board connection. They looked 'ok' I guess - slightly indented where they've been pushing down all these years, but ok, and I bent the copper down a teeny bit to be sure there was good contact. But I suppose I could reseat the connector and double-check the contacts. (BTW, all other lights are fine, so if it's the PCB it's only that branch circuit.)
I guess my question is this: besides these couple low-hanging fruits, does anyone know of other reasons that this might happen with just the one bulb? Is there a common failure that manifests with this symptom?
Follow up: during the inspection, he plugged in the OBD & said there was a code stored (the P1401 DPFE code, I think). After the CEL bulb was working the light was never came on after starting the engine. Of course the battery was disconnected while I did the work. So does unplugging the battery CLEAR a code or does the CEL just not come back on until it's triggered AGAIN. Also - I vaguely think an inspector once told me that one code stored was OK, but 2 was a fail. That seems like bunk to me, but it's part of why I ask the question.
Thanks!
Todd
