CM849 Barometric and ambient temperature

biggy238

biggy238

Active member
I installed a 2897333 (6.7L) combination sensor on my "bench" harness.

I can't get my CM849 to display anything other than 8psi baro and 160 degrees ambient. I've tried to rescale the baro. It isn't changing.

I have the same sensor connected to the intake horn and it reads correctly, albeit I have 5psi of boost due to the incorrect baro. Temp is 2 degrees higher than ECT cold soaked.
So, I duplicated the intake pressure scale for the baro. Still at 8psi.

I don't understand how the voltage axis works?

Can someone post a screen shot of a "deleted" baro sensor? I would like to keep the input for mountain driving. It may not play that great a role, but I don't want to find out that it matters while I'm away from home.

Thanks
Kyle

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I'm having trouble following you. So you're using a 5.9 ECM but are trying to use a 6.7 barometric sensor but you also want to delete this sensor? I have had zero problems rescaling the baro sensor for my truck. I repurpose the barometric pressure inpput for low side fuel PSI. I'm using an aftermarket transducer rather than a factory baro sensor. I no longer use the ambient air temperature sensor. My application is a 6.7 common rail running 5.9 electronics. I relocated my ECM to the cab so I built my own engine harness. I'm pretty familiar with the 5.9 harness and repurposing sensors. Just not exactly sure what you're asking for. Deleting the sensor is just simply turning off the DTC codes for the sensor and not using it.
 
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I jumbled that one.

I want to try and figure out how to rescale first. (I've tried and failed)

If that doesn't work, I need to delete it.

I'm suspicious this ecm was sold because the baro input is damaged.

I couldn't find the ambient temp input to scale it?

I've done what you have, 5.9 ecm, 6.7 peripherals. I built the harness(es).

I've turned some dtc's off.
Does that still leave the ECM calculating boost from a false baro reading?

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You may be on the right track. Scaling it is just as easy as changing the numbers in the axis. Michigan ACM sent out play farkle reference. The resistors in the sensor change that voltage based off temperature and that is the signal that's going back to the ecm. The ECM then interprets that signal and references the numbers that you punch in to that table.
 
I will post a shot of the axis table when I can get back to it.
I hit both circuits with a pot and monitored them in EFI (also used a cts2) and it never reacted.

These are from the 6.7 file I was using to compare my 5.9 file to.

I moved the floor on my 5.9 file up to 60.2 kPa but no change.
76d862efc90a2ce6b63c2d2119dd3f7b.jpg
201b6df600e4732d7e4e6fca71b7b2dc.jpg


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OK so this was self inflicted. I was off one pin at the ECM and had the signal wires swapped at the sensor. I'm sitting on 13.9 on inlet and intake pressure and temp matches ECT.
fc726244e7ded53683e783d612535919.jpg


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How concerned do I need to be with the 13.9psi ambient readings?

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