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--- 2gbaroinputworkaround [2012/07/02 08:58]
twdorris
+++ 2gbaroinputworkaround [2024/03/15 11:16]
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-====== 2G Baro Input Workaround ======
-The baro input of the 2G ECU may not be compatible with aftermarket sensors.  The 2G ECU has a 3.3K ohm pull-down resistor (R39 on 1995 EPROM ECUs), which may (probably will) put more load on the sensor than it can drive properly.
-For example, a GM 3-bar sensor can only drive this input to 1.76 volts at maximum pressure. The GM 3.3-bar sensor seems to have a bit lower output impedance and will drive the 2G baro input a little higher, but it's still unsuitable.
-Short of removing that resistor from the ECU (described below), the 2G baro input is suitable for use only with very low impedance sensors (even a 50-ohm output impedance will produce a little over 1% of voltage offset). Since most sensor designs have a resistor in series with its output for protection, the 2G ECU's baro sensor input is probably not suitable for use with most sensors.
-**OMNIPOWER NOTE:** The [[http://www.ecmtuning.com/product_info.php?cPath=28_30&products_id=47|OmniPower 4-bar sensor]] that we sell on our website *does* work fine on the 2G baro input.  This sensor incorporates a buffer circuit that drives the 2G baro input just fine.
-**GM MAF CABLE NOTE:** Also note that our GM MAF cable's "baro" [[gmmafiatbaro|breakout wire]] includes a buffer circuit as well.  So any sensor connected to a GM MAF cable's "baro" wire will work fine as well without having to deal with the 2G ECU's baro input resistor configuration.
-The 1G baro input doesn't seem to suffer from this problem. It has an input impedance similar to the 2G MDP sensor input's 100K ohms).
-**12/19/2007:** Instead of this process, you can also consider using the [[ECUInputData|buffer circuit]].
-====== Process ======
-If you're really looking to maximize inputs, you can consider removing R39 from the underside of the ECU board. **NOTE:** This is ONLY appropriate for a 1995 EPROM ECU.  It does not work on 96/97 ECUs.  A different resistor may be present on 96/97 ECUs that can be removed like the 95 EPROM ECUs, but we have not spent any time yet trying to identify it.
-It's best to use a couple small-tip soldering irons for this. Heat 'em up, apply one to each side of the resistor and slide it right off. I'm including a picture of the location of the resistor of interest below. I have verified that this does allow a GM 3bar to drive the baro input just fine. Once you have done that, you can use either the baro or the intake air temp inputs for whatever you want.
-{{http://www.dsmlink.com/images/forums/2gbaro.jpg}}

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