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i have a 2007 chevy silverado 6.6 turbo diesel it has been down for about 6 months cannot drive in reduced power mode due to a code po101 maf .i have replaced MAF with genuine gm one,egr valve,new dry air filter,have looked over all intake boots,boxes and lines no leaks,pcv lines complete,tried a new MAP sensor.still no change my only thing left is the ECM does anyone know how i can test the ecm to guarentee thats it i have wasted so much money trying to fix.cant afford to waste anymore if wont fix it.please any help or ideas.here are the OBD scanner readings i took after map sensor replacement hopefully they can help .at a idle warm ECT83(c),MAP87kpa,engine rpm 710,tps14.1%,MAF41.03(g/s),IAT22(c),fuel pressure31840(kpa),MILdis2(km),catTe12 500c,cat Te11 19c,BARO99kpa,Clr dist 2km,Ambient 13c,Rel tps 100.0%,Eq ratio 0.625,Ecu volts 14.486v .if anyone has delt with or notices something out of place please let me know.or how i can test the ECM to confirm its bad.please any help i really need it fixed thank you
 

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Relocated over to the LBZ section of the forum for more appropriate answers to your issue.

:thumb:
 

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Is your truck tuned? If so, flash it back to stock and see if any other codes pop up.I had a very similar situation and the only code at first was P0101. Did similar things as you such as replacing the MAF, to no effect. Upon reflashing it back to stock and driving a short distance it also popped an underboost code, this helped me narrow it down and it ended up being the turbo.
 

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Just a thought...have you considered puling the battery cables off for 5-10 minutes or so.?? Only takes 5 min and no cost. Ya never know - I've seen stranger things.

As for your OBD Scan readings...may have better luck using Imperial..? Most of the guys here are US Based.?

Good Luck
Theo
 

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Here is step #1 for you:

Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
Ignition OFF and scan tool disconnected for 90 seconds, test for less than 5 ohms between the MAF low reference circuit terminal 2 and ground.

If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

Ignition OFF and scan tool disconnected for 90 seconds, test for less than 5 ohms between the IAT sensor low reference circuit terminal 4 and ground.

If greater than the specified range, test the IAT sensor low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 3 and ground.

If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 1 and ground.

If less than the specified range, test the MAF signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
If greater than the specified range, test the MAF signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
 

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Discussion Starter #7
thank you i will try anything right now to get it going.thanks ron i found this test on another site and it was by you.i performed all of this and everything checked ok and says replace the ecm from your test.so i will do it again to confirm.my question is there a pin test or something i can verify the ecm is faulty ive thrown so much at it im kinda scared to replace the ecm and have it do the same thing.thank you so much for all your input i will recheck and let you know thank you again
 

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If you checked not only the tests specified but made SURE there are no shorts to power or ground, no frayed wires, no corrosion at the connectors, etc, there is really no need to test myriad of other pins on the ECM because if the ECM won't support the requirements of the MAF/Iat sensor which are required for a running, working engine, the truck just won't run correctly, ever. I suggest you contact John Kennedy at (715) 255-9433 who can provide a pre-programmed ECM specifically for your vin# at a very reasonable price. If he thinks you need a new ECM, you need a new ECM.

When you receive your replacement, all you have to do is to turn key off, unplug your old ECM and plug in the new ECM. Turn on and start your truck. It's that simple.
 

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Discussion Starter #9
thank you ron.so the only reason i can say the ecm is cause of the 2 tests maf low term2 to ground and iat low term 4 to ground to check for 5 ohms or less tested at 6 ohms.other than that was all in specs.i cleared the code and test drove this morning the reduced power did not come on. but the po101 set within a mile it ran good but i noticed it was blowing alot of black smoke when i accelerated.thank you again ron
 

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Is it possible that there is some corrosion on the connector to the MAF/IOT? Or the corresponding connector at the ECM? Or perhaps the ECM ground to the body/engine? 1 ohm is a very small amount, but enough to make the circuit out of spec. Check for poorly fitting pins at the connectors, backed out pins, etc. I would buy, if not on hand, some Deoxit contact cleaner and spray those connections and grounds and see if you can get the resistance lowered a little. Way cheaper than a new ECM plus programming.
 

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Discussion Starter #11
thank you ron.im thinking something like that i just ordered the maf pigtail.another thing i noticed so at the begining of your diagnostics chart it says key on with the scanner the BARO and the MAP are suppose to be within 4K of each other there not baro 99k map 87k and i followed the diagnostics for that wich said replace map so i did it changed nothing.i guess thats were i get lost when diagnostics say replace something and it does not fix it and electrical parts cant return lol.i will keep you posted thank you very much for the help and ideas.think of anything else please let me know thanks
 

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I'm looking at post #6 and I don't see that comparison test. Where is it? I know that my BARO and my MAP are not the same, though in theory they should be, engine off. My BARO is 28.6 and my MAP is 28.1 both inHg (inches of mercury). What unit of measure is 4k?
 

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the BARO and the MAP are suppose to be within 4K of each other there not baro 99k map 87k and i followed the diagnostics for that wich said replace map so i did it changed
I think your measurement was likely in kPa or kilo pascals. My truck, key on engine off has a reading of 97kPa for BARO and 95.3 for MAP. So the question is was your engine running? It definitely makes a difference. And at what altitude are you located? Where are you?
 

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Discussion Starter #14
its in my first post 87kpa map and baro 99kpa and its around the same everytime key on engine off .for the diagnostics said replace map wich i did still has same readings with new map sensor.thank you very much for the help ron. i did order the plug for the maf as soon as i get it will let you know if there is any change thank you
 

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87 kPa MAP is about equivalent to 4000 ft in altitude; 99 kPa BARO is about equivalent to 1000 ft in altitude. Which one matches where you are?
 

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Discussion Starter #17
my altitude is 397ft above sea level .i replaced the harness plug got a mile down the road engine light po101 reduced power barely got it back.i assume the readings look good cause no one has commented on anything being out of specs.is there anything else i could check or look for causing this code and reduced power.new maf,map,egr,maf harness,dry air filter,no air leaks between air filter and plastic tube that connects to the turbo.i just dont know what to do.thank you for all the help
 

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Discussion Starter #19
hello HWI yes it does really bad black smoke under throttle even kinda felt like a gas engine missing under heavy throttle as it poured out black smoke.please let me know what your thinking thank you
 

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So the truck is clearly not building boost, but it is delivering the fuel. Based on everything else you have done without any results, I would lean towards a turbo issue. Do you know someone with a Tech 2 that can manually sweep the vanes? I'd start there.
 
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