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Thread: Maf voltage issue

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Posts: 11-12 of 12
2009-06-16 17:35:08
#11
Originally Posted by WingmanSR20
one thing to remember (at least how i was taught) is the MAF is measured based on the difference between the positive voltage and the ground wire voltage. Therefore, you want the MAF's ground to be as consistent with the ECU's as possible.

For example, the ECU ground might actually be -11.2V, so if you ground the MAF directly to the battery negative (-12v), you could be off by that much (0.8V), possibly more. However, if you ground the MAF to the same spot as the ECU so it too has a -11.2V ground, then it's more accurate.

Those connections on top of the intake manifold help you accomplish that.

If I'm wrong, though, please someone correct me.


That makes sense, I'll try that later today. Thanks.
2009-06-16 18:30:32
#12
Wingman, You are exactly correct! Great explaination of the grounding differences..

Most people think the battery ground is good for underhood grounds (MAF ground mod, sensors, etc..).
Its actually much worse as you described clearly here.
Additionally, I have found the normal battery ground readings of -13.4 to -14.2. This makes your difference with the Intake Mani much greater.

Im doing a couple of howto writeups and will definitely reference your great description/explaination...

Your MAF reading can be less than 1v with key ON & no idle. The true test is with the engine running..
The DE MAF reading is normally in the range of 1.3-1.7 with car running (only after engine reaches full operating temp).
Different MAFs has multiple voltage ranges; refer to the FSM for your MAF voltage range. If voltage is lower or higher, swap the MAF for a known good MAF to validate your readings (to determine if wiring or maf problem).
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