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Code P0446 EVAP System Check Engine Light
- Thread starter jhowell9618
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rrwhitman
Active Member
Replaced the harness, cleared the codes, and no more check engine light or new codes. Key to working on the hoses, sensors and harness on top of the tank is to have it close to empty, support it with a floor jack, and lowering it down enough to gain access to everything. With the front of the truck on ramps I was able to slide under and then squeeze my torso between the muffler and the drive shaft and have everything pretty much right in front of me. I haven't used the FORScan software to check anything again but I don't know if it is necessary. I may do it just to see the various sensor voltages, etc... for my own edification. Thanks to all the contributors. If anyone has any questions that I can help with after doing this repair I will be glad to help. Cheers.
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RangerBill
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Good to hear it is fixed.
airline tech
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Awesome - I suspect the signal wire was the chewed wire
rrwhitman
Active Member
Just to follow up - I took a look with FORScan and observed the FTP sensor voltage changing as the tank pressure fluctuates. The tank is at a slight vacuum when the engine is running and when vented to atmosphere the sensor puts out 2.62V. I don't think there was anything wrong with the original sensor after finding the chewed-up wiring but so it goes. Still, it was still educational to see the live data. Also, two 'permanent' DTC codes that were still present (but not resulting in a CEL) have cleared following some starting/driving cycles. No codes at all now - pending, permanent or current. So, all good. Cheers.
airline tech
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That's good news - I look at it this way - the sensors on that tube have history of failing, so the extra money spent was preventive maintenance - since this is limited access, but on the other hand that wire shorting could have also caused the sensor to short internally as well. - I do not think you wasted any money and it was good to just replace both - due to limited access. If this was wide open - I would say return the tube assembly or at least try the old tube back installed.
I am just glad it was discovered before you put the tank back up and go - maybe just need to add gas - and then back at square one and eventually dropping the tank again for a final fix.
I am just glad it was discovered before you put the tank back up and go - maybe just need to add gas - and then back at square one and eventually dropping the tank again for a final fix.
rrwhitman
Active Member
Tech, thanks for all of your input and information. I don't feel bad about replacing the hose/sensor assembly after reading about the history of them failing. I actually had put it all back together and drove it with the fault on an 800+ mile trip before the harness came in. Simple planning to have the tank empty when I returned. Lowering the tank down is actually very easy once you've done it and know all the right angles, how to position yourself, etc.. - just a pair of ramps, a floor jack and two 15mm bolts.
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