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  #1  
Old 08-19-2006, 09:40 AM
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Default MAP Sensor

Ok folks.. here's a question.... the MAP sensor... is it used in the fuel system also or just for feedback to the shift algorhythms?? ALSO is there a bench impedance (resistance) test I can do with a meter on it to make sure it's within spec. I think mine might be out of spec. or just dirty or something cause it seems like I REALLY gotta romp HARD on the pedal to drop into passing gear and it seems like my tranny shifts a bit soon... (seems like it wants to stay TOO low in RPM)
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  #2  
Old 08-19-2006, 10:43 AM
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Default RE: MAP Sensor

Quote:
MAP Sensor Description & Operation:
The Manifold Absolute Pressure (MAP) sensor responds to any changes in the intake manifold pressure. The pressure changes as a result of the engine load and speed. The MAP sensor converts this to a voltage output.

A closed throttle on the engine coast down would produce a relatively low MAP output voltage. A Wide Open Throttle (WOT) would produce a high MAP output voltage. This high output voltage is produced because the pressure inside of the manifold is the same as outside the manifold. The MAP is inversely proportional to what is measured on a vacuum gauge. The MAP sensor is used for the following:

* Altitude determination
* Ignition timing control
* Exhaust Gas Recirculation (EGR) diagnostic Speed density fuel management default

When the VCM detects a malfunction in the MAP sensor circuit, the following DTCs will set:

* DTC P0106 Circuit Performance Malfunction
* DTC P0107 Circuit Low
* DTC P0108 Circuit High
* DTC P1106 Intermittent Circuit High
* DTC P1107 Intermittent Circuit Low
Other than that, my references do not have any further information on the diagnosis of a faulty MAP sensor. With my scan tool, I was able to monitor the voltage from the MAP sensor and I saw drop outs under constant throttle & RPM. After checking the wiring, I replaced the MAP sensor. This fixed my slight miss under light load conditions as well as made my transmission shift smoother.

This does affect the way the transmission shifts in that it is what the PCM uses to calculate engine load. So the calculated engine load as a function of the TPS voltage and the MAP sensor voltage gets translated into how and when to shift the transmission.
  #3  
Old 08-19-2006, 05:13 PM
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Default RE: MAP Sensor

What scan tool do you use??
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  #4  
Old 08-19-2006, 06:13 PM
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Default RE: MAP Sensor

I have an AutoEnginuity, but although it is MUCH more advanced than my old scanner, I still prefer the interface of my old one (which Jman now owns). I used to have an Autotap scanner.

My new autoenginuity scanner can do everything that a GM Tech 2 scanner can do except update software or change variables.
  #5  
Old 08-19-2006, 08:13 PM
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Default RE: MAP Sensor

I have a 95 Blazer and have been told that some of GM's vehicles had OBD2 on the 95 (seein' as how OBD2 started in 96) is there any way I can tell which one mine has?? OBD1 or OBD2???
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  #6  
Old 08-19-2006, 08:29 PM
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Default RE: MAP Sensor

Here is a list that may help:

http://www.obdii.com/connector.html
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  #7  
Old 08-19-2006, 09:41 PM
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Default RE: MAP Sensor

Eh.. You are actually SOL. Chances are that you have the bastardized OBD1.5 which utilizes afew OBD2 protocols, has an OBD2 connector, but still retains some of the OBD1 protocols. It's a real pain to do anything with. If you take your truck to Autozone and they can't scan it, then yours is an OBD1.5 and there are VERY few scanners that are capable of showing you what's going on (GM Tech 2 aside).

If you really wanted to get into diagnosing your '95, I would invest in a good oscilliscope and some test leads. That will be my next purchase just cause they flat out give you the data!
  #8  
Old 08-19-2006, 10:28 PM
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Default RE: MAP Sensor

Hey I not for sure on this but your's (being a 95) could still have the adjustable Throttle Valve cable. See if there are three cables on your throttle body 1 for cruise, 1 for throttle, and 1 for trans throttle valve (commonly known as kick-down cable) If you do have it holla back and I'll walk ya through the adjustment process. As far as OBD 1 and OBD 2.....OBD 1 has a 12 pin DLC......OBD2 has a 16 pin DLC.
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  #9  
Old 08-19-2006, 11:20 PM
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Default RE: MAP Sensor

heh... I have a scope....LMAO
I just wanted realtime data with a GUI... I'mma geek....




know WHAT... I never even THOUGHT to look for the old "detent cable" (think that's how ya spell it) I'll do that tomorrow... if so I can just take a little slack outta it and get it to shift about where i want....:P GOOD catch DOOD! THANX
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Old 08-19-2006, 11:20 PM
 
 
 
 

Tags
95, 96, blazer, cable, change, chevrolet, chevy, function, location, map, operation, p0107, s10, senosr, sensor


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