MAP Sensor Bad?
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Mountain Pass
Joined: Aug 2006
Posts: 203
Likes: 6
From: Port St Lucie, FL
MAP Sensor Bad?
Ok trying to figure out if my map sensor is bad or something else going on. I keep getting code 1248, from which I have read is no boost/low boost detected. I know I am building boost because of my boost gauge and it is teed into the map line so I would think there is pressure going to the map sensor. I just got torque pro yesterday now that my adapter came and all configured today finally I have more things to go on. On torque pro I am getting a constant 14.6 reading from the map and get -0.2 on the boost from torque. I have checked the equations about 10 times thinking that was my problem but then remembered I had been getting that 1248 code. I do have the boost fooler on my truck, would this cause any problems like this? Does no map reading mess with tuning on the truck as well? Before I go and buy a new sensor wanted to get some feedback. Thanks!
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Mountain Pass
Joined: Aug 2006
Posts: 203
Likes: 6
From: Port St Lucie, FL
Yep checked it all and everything looks ok but I will get some new hose tomorrow and replace it just to rule that out. Pins and wire look fine and when I unplug the sensor it throws a CEL so I am assuming it’s getting signal just not proper signal. Anything else to check?
More Turbo
Joined: May 2016
Posts: 717
Likes: 9
Yep checked it all and everything looks ok but I will get some new hose tomorrow and replace it just to rule that out. Pins and wire look fine and when I unplug the sensor it throws a CEL so I am assuming it’s getting signal just not proper signal. Anything else to check?
You can use a DMM to determine if the Sensor is operating correctly - 5vRef and Hz (Duty Cycle). A scope is easier and more accurate as a RMS will average the % rather than being able to view it 20ms. But, will work in a pinch.
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Mountain Pass
Joined: Aug 2006
Posts: 203
Likes: 6
From: Port St Lucie, FL
Ok I will remove the boost fooler tonight and put a new hose on straight from the manifold to the map and see what happens. This will remove the t fitting, boost fooler, and any possible cracks in the current line. If that doesn't work I will have to get out my meter and learn how to do that duty cycle on it. I know enough to check voltage and be dangerous to play with it so I am sure I can find a youtube on it lol. If not I guess a new sensor will be on order. When I unplugged it yesterday and drove the truck up to the store, I had so much better power in the truck again, so tuning must rely on map for fueling or something. Interesting enough when it is unplugged torque pro gets a reading from the map, so assuming the pcm uses some sort of default table as well with the CEL on.
Postmaster
Joined: Sep 2007
Posts: 4,195
Likes: 6
From: Medford Oregon
Yes, PCM uses default tables with the MAP unplugged. Also MAP does determine fueling big time. Usually if the truck runs much better with the MAP unplugged then the MAP is bad. However in this case I suspect a bad boost fooler. Your plan is good, replace the hose and eliminate the tee and boost fooler first. MAP sensors are expensive and seldom fail.
Troubleshooting MAP with just a voltmeter is almost impossible. A digital voltmeter with a HZ scale works great. Unfortunately most lower end digital voltmeters do not support that option, some do though.
Troubleshooting MAP with just a voltmeter is almost impossible. A digital voltmeter with a HZ scale works great. Unfortunately most lower end digital voltmeters do not support that option, some do though.
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Mountain Pass
Joined: Aug 2006
Posts: 203
Likes: 6
From: Port St Lucie, FL
Well you were spot on thank you. Put a fresh line on and it worked like a charm. Put the t back in line and worked great as well. So without the boost fooler hooked up it works great so must be failed boost anihilator, which is surprising because I thought it was just a air regulator. Well does anyone know if DP tunes out the overboost code now? It used not to and is why I put it in but now that I just got it reflashed with new tunes and now no boost anihilator it seems map its only seeing 21.9 while my boost gauge is reporting more. Anyways my truck is alive once agian and I would of never known without torque pro to lead me in right direction and the help of you guys to suggest the fooler.
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Cargo Master
Joined: Aug 2009
Posts: 2,137
Likes: 13
From: Glendive, MT
How much boost are you making?
Any more than about 25psi can be hard on the map sensor.
I'm running an OCR from RiffRaff. OCR - Overboost Code Regulator for Ford 7.3L 99-03
Any more than about 25psi can be hard on the map sensor.
I'm running an OCR from RiffRaff. OCR - Overboost Code Regulator for Ford 7.3L 99-03
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Mountain Pass
Joined: Aug 2006
Posts: 203
Likes: 6
From: Port St Lucie, FL
Currently only seeing about 22-24 max. About to put in wicked wheel 2, RiffRaff billet plenums, new RiffRaff cac boots, and bellowed uppies. So hope to seal up any leaks and be making more very soon. So your saying I should buy a new boost fooler to save the map from seeing such high pressure, even if overboost is tuned out?
Cargo Master
Joined: Aug 2009
Posts: 2,137
Likes: 13
From: Glendive, MT
I would. I think it was Bill at PHP that had an article on map sensors. I'll see if I can find it.
There is a thread on PowerStroke Nation titled 35psi Map Sensor that has a brief explanation.
There is a thread on PowerStroke Nation titled 35psi Map Sensor that has a brief explanation.
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