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MAP sensor for gauge

michbc3

michbc3

Well-Known Member
Ok. I understand that the factory boost gauge in the instrument panel (IP) is mostly for laughs, but I'd like to try to get mine to work a little better. There may be hope. I think that if I replace the gauge MAP sensor, I'd be a lot closer. Does anyone know what part number that is - and where I might be able to buy one? Dealer? Pep Boys? Internet sources?

When compared to my Autometer gauge, the gauge in the IP consistently reads about 10 units higher. For instance, with the engine not running, but key "on", the IP gauge reads 10 psi. With the engine running at idle, the gauge falls to 0, probably because the sensor is seeing vacuum. And 5 psi of boost on the Autometer gauge show 15 psi on the IP gauge.

So I think that the IP gauge may be OK - but the MAP sensor that it uses may be damaged - or perhaps even an incorrect part that was swapped in there before I owned the car. Would this be a 2 or a 3 bar sensor?

Note that my ECM is an Accel GEN7+, and it uses a completely separate 3 bar MAP sensor to run the engine itself.
 
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The original sits on top of the evap box and it is a 3 bar map sensor. I don't have a part number but it is still available from GM under the '89 TTA with LC2 engine. ...It's not cheap, like around $80+
 
Ok. I called Pontiac today and they list 16040749. The part number is listed twice in their system - with two (!) different prices. You can pay $114.72 or $162.13. On NewGMParts.com one can pay $81.63. I like that better. Thanks to you I now know that it is a 3 bar MAP. A critical piece of info. So maybe I can find it at a regular auto parts store - even cheaper. Thanks!
 
Remember the pin out changed .... look at the adapter you have on the stock OEM setup as I beleive 2 pins are swapped around ... just something to take into consideration when you replace the MAP
 
michbc3 said:
Ok. I called Pontiac today and they list 16040749. The part number is listed twice in their system - with two (!) different prices. You can pay $114.72 or $162.13. On NewGMParts.com one can pay $81.63. I like that better. Thanks to you I now know that it is a 3 bar MAP. A critical piece of info. So maybe I can find it at a regular auto parts store - even cheaper. Thanks!
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It is $53.89 at this GM online dealer

http://www.trademotion.com/partlocator/index.cfm?siteid=214632
 
I typed up a nice long response before but then my computer froze.

Basically what it said is that more than likely it's not your MAP sensor that is off, it's the actual gauge itself. The gauge is electronic from a time in which we really didn't know what we were doing. So if you actually want it to be accurate then you will have to have the gauge itself tuned and/or rebuilt, and I hope you have stock in some vaseline. The gauges were inaccurate from the time they left the show room and between age and wear and tear they're even more inaccurate now. If I were you I'd cut my losses and just run something discrete like the powerlogger which I believe will tap into your MAP sensor and give you an accurate pressure reading.

Part of the reason I don't think that it's the MAP is because the MAP on our cars are actually very popular in the aftermarket world. Quite a few of the stand alone systems use the GM 3 bar MAP from our cars (I believe FAST is one of them). Do a search on google for 3 bar MAP sensor, all you'll see is how to install them on other cars and use them with different tuning software. It's a quality piece, our gauges however are not.
 
Thanks for all the input. I did not know about two different designs. The reason that I think that the IP gauge is OK is because the "error" is consistently 10 units off. Key off, engine off, it reads 0. Turn key to run, but engine not runnng, the IP gauge reads 10 psi. Start the engine, it goes back to 0 - probably because the engine is pulling vacuum. When the turbo is developing 5 psi of boost on my Autometer gauge, the IP gauge reads 15. If I make 10 psi on the Autometer, the IP gauge reads 20. If the IP gauge did not read 0 with the key off and at idle, I'd question the gauge a lot more.

The GEN7 ECM on this car uses a separate 3 bar sensor. So I have two 3 bar MAP sensors under my hood.

According to cell 8A-81-0 we've got 5 volts across the MAP boost gauge sensor. The gauge reads that voltage. If I could probe the leads with a voltmeter, it would be interesting to see what it says...
 
Just to let you know that I recently placed an order for the MAP sensor from TradeMotion.com, initially for $53. The next day I got an email that said that their price increased to $83. Since this was about the same as my other sources, I placed the order. Standing by for delivery...
 
It took me 5 minutes to install a new 3 bar MAP sensor to replace the one that drives the factory instrument panel (IP) boost gauge yesterday. I'm happy to report that it now works just fine. It tracks very closely with my external Autometer boost gauge (probably within 1 psi at or near full scale).:thumbup:

I believe that the reason that the original MAP sensor failed was either because the car had been hammered with excessive boost by a previous owner (a wild and crazy guy running 29 psi who eventually blew some head gaskets!) or a backfire.

Of course, even though the factory IP gauge is now working correctly, I'll continue to rely on the Autometer gauge as my "standard". But I like to have all of the gauges working in my car if possible. Further if either the IP gauge or Autometer disagree with one another in the future, I'll know to look for trouble.

Of course if you are regularly using much over 20 psi of boost and your MAP sensor is broken, then it's probably a waste of time and money to replace the MAP. But I think that my experience is worth sharing - especially for those with unmodified cars. :yes:
 
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What is the link for the sensor.
Part Number ????
What is the brand?
I can't find it at TradeMotion.com.......

Thanks
 
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This part is an ACDelco: 12223861. The cost is now $78.43 on GMpartsdirect.com.

I find that TradeMotion web site hard to work with and they now charge more anyway.

Best, Bob
 
michbc3 said:
It took me 5 minutes to install a new 3 bar MAP sensor to replace the one that drives the factory instrument panel (IP) boost gauge yesterday. I'm happy to report that it now works just fine. It tracks very closely with my external Autometer boost gauge (probably within 1 psi at or near full scale).:thumbup:

I believe that the reason that the original MAP sensor failed was either because the car had been hammered with excessive boost by a previous owner (a wild and crazy guy running 29 psi who eventually blew some head gaskets!) or a backfire.

Of course, even though the factory IP gauge is now working correctly, I'll continue to rely on the Autometer gauge as my "standard". But I like to have all of the gauges working in my car if possible. Further if either the IP gauge or Autometer disagree with one another in the future, I'll know to look for trouble.

Of course if you are regularly using much over 20 psi of boost and your MAP sensor is broken, then it's probably a waste of time and money to replace the MAP. But I think that my experience is worth sharing - especially for those with unmodified cars. :yes:
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Glad you got it sorted! As the MAP also feeds the ECM (if I remember correct) this can only be a good thing for you :-)

So was the new GM replacement just to plug in or did you have to swap the wires around or not?? Just so I know if mine goes bad at some point.
 
Hi again folks. I was unaware of any design change issues. I just plugged my new MAP sensor into the same connector as the old part - and it tracked well across the range of boost pressures that I tried (like 2 psi to 16 psi). I will defer to Razor's excellent postings in the TurboBuick link above if anybody has trouble after doing what I did.

If pins A and C are reversed, no damage would occur to the MAP sensor or gauge, but the readings might be off until the wiring is corrected.

Another thing that may or may not be a myth is that my friend told me to mount the sensor vertically as opposed to what I found: sensor mounted horizontally. There was something mentioned about dirt accumulation over time... So I just added a little 90 degree bracket and a screw from home depot to accomplish this.
 
I'm wondering if a have a faulty MAP too, since my boost gauge is not working also. Do all the TTA's have that 3-4 inch mini harness at the MAP that looks like it has a resister built in & reverses the wires? Does this mini harness get used with the new style MAPs? I can jump the 2 pins at the MAP & my gauge goes to 20psi.
 
Cool, thanks for the link. Question thow, if the new MAP internals are wired reverse & my car already has the small resister harnss the reverses them already, does it just plug in to that mini harness, or does that have to be reversed or eliminated?
 
If I remember correctly...the 2nd design MAP,which is the one everyone uses now, you just eliminate the extra harness.
 
Well, I hooked up my mighty vac hand pump to the MAP, (key on, engine off) applied 18-20 inches of vac to see if I can get the gauge to at least move & got nothing. I even took out the mini harness & plugged it straight to the main connector & got nothing also. But I can still jump the green & gray wires at the MAP & the boost gauge goes instantly to 20psi. I'm assuming its the original MAP (has no part # on it) but, it could be different one also, since I just got the car recently. I'm kinda thinking its a bad MAP & to put the 2nd design one on & retry? Would I need the pig tail also? Heres a few pictures of the MAP & mini harness, is this on all TTA's?
 
I have no reversing wiring harness like you showed in your pictures - on my car. I've heard that others need them though. Now, regarding using the MityVac hand pump, make sure that you are applying pressure, not vacuum to the MAP. If you are applying vacuum, it won't do anything of course except sit at 0. Because you can make the gauge go to 20 when supplied with voltage, your gauge is working fine. It's just a matter of getting the MAP sensor hooked up correctly.
 
michbc3 said:
I have no reversing wiring harness like you showed in your pictures - on my car. I've heard that others need them though. Now, regarding using the MityVac hand pump, make sure that you are applying pressure, not vacuum to the MAP. If you are applying vacuum, it won't do anything of course except sit at 0. Because you can make the gauge go to 20 when supplied with voltage, your gauge is working fine. It's just a matter of getting the MAP sensor hooked up correctly.
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Good call on the applying pressure, thats were I DontKnow: up (first turbo car). So I applied light pressure to the MAP while watching my gauge (key on engine off) & it worked. On the new 2nd designed MAPs part# 12223861, were does the new pig tail attach too, is it from the main harness or the mini harness that I already have on there? (see pictures) Or do I even need the pigtail with the new MAP? Thanks for any ideas!!!
 
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TURBO1 said:
Good call on the applying pressure, thats were I DontKnow: up (first turbo car). So I applied light pressure to the MAP while watching my gauge (key on engine off) & it worked. On the new 2nd designed MAPs part# 12223861, were does the new pig tail attach too, is it from the main harness or the mini harness that I already have on there? (see pictures) Or do I even need the pigtail with the new MAP? Thanks for any ideas!!!
Click to expand...

The mini harness is the pigtail, at least in my case it was. I tried it "part# 12223861" from the main harness and it didn't work and worked fine from the mini harness.
 
The mini harness thats on mine now, has a resister built into it, but it is reversed & for a 1st designed MAP. I need to do some more research :detective: & find out were the pig tail ends tap into, if I do need it.
 
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