TPMS Thresholds
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Fleet Mechanic
Joined: Jan 2005
Posts: 1,784
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From: Tomball, Tx
TPMS Thresholds
Does anyone know what the TPMS low pressure (alarm) threshold is?
I want to lower the pressure in the tires a bit, but don't want to set off the warning light.
I know the numbers can be adjusted w/ forscan but I don't have that capability YET.
I want to lower the pressure in the tires a bit, but don't want to set off the warning light.
I know the numbers can be adjusted w/ forscan but I don't have that capability YET.
More Turbo
Joined: Apr 2017
Posts: 628
Likes: 12
From: Madison WI
Not that this necessarily answers your question, but I let 10 PSI out of the rear tires, took them from 75 to 65 PSI. They were rock hard from the dealer, and its unlikely I'll be hauling anything anytime soon that would require maximum pressure Next key start cycle, the dash read the new pressure, no warnings. I seem to remember reading a percentage of drop that would activate the sensor.
According to Ford's official owner website for my truck, it tells me:
TPMS Operation
The tire pressure monitoring system (TPMS) illuminates a low tire pressure warning light when one or more of your road tires are significantly under-inflated. However, TPMS is not a substitute for proper tire maintenance, and it is the driver’s responsibility to maintain correct tire pressure. It is possible for your tires to be partially under-inflated even if they are not so severely under-inflated that they trigger the TPMS warning light.
I see "significantly", "partially", and "severely" all mentioned, with no further explanation or definition.
According to Ford's official owner website for my truck, it tells me:
TPMS Operation
The tire pressure monitoring system (TPMS) illuminates a low tire pressure warning light when one or more of your road tires are significantly under-inflated. However, TPMS is not a substitute for proper tire maintenance, and it is the driver’s responsibility to maintain correct tire pressure. It is possible for your tires to be partially under-inflated even if they are not so severely under-inflated that they trigger the TPMS warning light.
I see "significantly", "partially", and "severely" all mentioned, with no further explanation or definition.
Senior User
Joined: Apr 2005
Posts: 471
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Just air down to what you want to run and see if it set the icon on. If it don't then you know. If it does turn it on just start putting a few pounds of air and wait a few minutes to see if it resets. That's what I did and I know I could lower my pressure.
Tuned
Joined: Oct 2013
Posts: 281
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From: Gen. 7 Texan
So I just bought the new truck in sig and need to know if it is possible for dealership to change tpms values like my 2013. I'm not asking if they want to but if it is possible for a tech to do it...thanks in advance!!
Fleet Mechanic
Joined: Dec 2006
Posts: 1,756
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From: Maryland
It is possible; will they, another question altogether.
Thread Starter
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Fleet Mechanic
Joined: Jan 2005
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From: Tomball, Tx
Can anyone confirm the following -
According to the 2017 Codes for Super Duty (spreadsheet) the defaults of 3C50 is 80 psi - but mine are already below that (according to the dash).
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New User
Joined: Apr 2017
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Per the FMVSS standard, the dash indicator has to come on within 20 minutes of a tire dropping 25% from the normal inflation pressure. Nothing says it can't come on before it drops 25%, so it could be less on this particular vehicle, but the systems are designed to try and avoid "over-alerting" drivers so they don't just totally ignore the light.
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Junior User
Joined: Jan 2017
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From: Edmonds, WA
I am going to go out on a limb and guess that the stock threshold is 65psi. In forscan you can choose 50-65psi in 5psi increments and I am pretty sure my code was set for the 65psi before I dropped it to 50psi. Changing 4 letters/numbers in a BCM code is how it is done for those who having tried forscan. I have read that some people are able to get down to 60psi stock, so there also has to be some variables built into the computer program. Without forscan, try 65psi for a few days and see what happens, then try 60psi.
New User
Joined: Apr 2017
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This is a bit of a semantics argument, but I don't think there is a "programmed trigger point". There is only a "programmed normal inflation pressure". If the pressure drops by some percentage from the normal inflation pressure, the light comes on. That percentage, by law, has to be 25% (or less).
If the tire inflation door placard in your trucks says 80 psi, the light has to come on around 60 psi.
If the tire inflation door placard in your trucks says 80 psi, the light has to come on around 60 psi.
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Fleet Mechanic
Joined: Jan 2005
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From: Tomball, Tx
it seems illogical to me.....
If the system looks at a drop over time (iirc someone said 20 minutes) the tire could FLAT before the light ever came on (thinking if its parked or shut off frequently by short trips to the grocery store etc).
If the system looks at a drop over time (iirc someone said 20 minutes) the tire could FLAT before the light ever came on (thinking if its parked or shut off frequently by short trips to the grocery store etc).
Junior User
Joined: Jan 2017
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From: Edmonds, WA
+1 I can understand a small delay in the signal to keep the TPMS light from flashing as the pressure bounced up and down by 1psi, but there has to be a set limit to turn it on and then stay on for a certain amount of time. An intermittent light on the dash would drive me nuts.....
Elder User
Joined: Aug 2006
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the numbers can be changed/programed w/ the FORSCAN software, a (windows) laptop and a bluetooth OBDII connector.
Can anyone confirm the following -
According to the 2017 Codes for Super Duty (spreadsheet) the defaults of 3C50 is 80 psi - but mine are already below that (according to the dash).
Can anyone confirm the following -
According to the 2017 Codes for Super Duty (spreadsheet) the defaults of 3C50 is 80 psi - but mine are already below that (according to the dash).
Can FORSCAN just turn it off? Maybe set to zero?
Post Fiend
Joined: Apr 2004
Posts: 5,158
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From: North of Salt Lake City
I suppose that's possible with FORScan. I don't know of a setting to disable it completely but you could accomplish the same thing by setting the threshold to 10 or 5 or even 0 psi. I haven't heard of anyone doing this yet so if you try, report back on the FORScan spreadsheet thread and I can update the description.