1997 K1500 MAP sensor

I've owned my truck for 4 years with no issues/codes. Just started getting P0430 Catalyst Efficiency below threshold (banks 1&2). What kind of readings should I see on my live database OBDII scanner for the MAP
info (in. hg)? I get 8.8 at idle, as I ramp up engine rpm I see 9.3 & as I slowly come back to idle it might go down to 6.5 & then go back to 8.8. Doesn't sound good to me. I'd expect a higher reading at idle.
Where is the MAP sensor located? Anyone? Thanks
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Depends on the engine load.

Why would you expect a higher reading at idle? MAP = BARO minus vacuum. KOEO MAP should read close to what the weather report says the barometric pressure is. KOER MAP should read that BARO reading minus engine vacuum

Top right side of the intake plenum just to the right of where the injector harness plugs in.
At this point I should probably mention that the MAP sensor on this vehicle has very little to do with anything once the engine is running, it is primarily used for a barometric pressure reading, it is also used as an engine load sensor if the MAF sensor fails.
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On 8/20/2010 9:22 AM, aarcuda69062 wrote:

I miswrote - I should have said I would expect a much greater differential between idle(high vacuum signal) and substantially higher engine rpm(lower vacuum signal). BARO at this point would just be an offset amount.

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One of the standard tests for diagnosing a restricted exhaust is to compare engine vacuum at idle and then 2500 RPM, at 2500 RPM the -vacuum- should be -higher- (lower MAP) than what was measured at idle. Higher RPM does not mean the engine is under a heavier load.
To achieve the observations you desire, you need to actually have the vehicle in gear and under load (driving). It would be more useful to observe the engine load PID.
FWIW, the P0430 code does not necessarily equate to a plugged catalytic convertor (if that is why you were looking at MAP).

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