Help with engine power reduced

dinkrdsw313

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Sep 26, 2022
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Thanks for the add to the group, I bought this today 2007.5 LMM , I’ve worked on duramaxs at work but first one I’ve own personally, somtimes the dash says “engine power is reduced” but runs fine when it pops up doesn’t loose speed it will get up to atleast 80mph with it saying that, but I noticed it will blow black smoke if you give it hard throttle, curious if the MaF will effect it I put my autel scanner on it since I don’t have a special scanner yet for diesel, and my MAF seems to be reading lower then every one says there’s is, I attached the picture, also my TP % at idle says 99.6%. F81D7553-5B56-4FA3-B5E1-07BB482A4608.png
 

08lmm72mm

Active member
May 13, 2019
528
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Saskatchewan, Canada
Any codes ? Is it stock? Is it tuned? What gear speed and rpm does it do it? I know lmms had an issue with the reduced engine power years ago but didn't affect performance, mine used to do it on older tune files.
 
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dinkrdsw313

New member
Sep 26, 2022
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No codes, besides glow plug # 8 issue, at one time I did get the scanner to read P0102 as soon as it popped up but it hasnt came up since, and I belive it’s stock I just bought it and it had a PPEI in the console but I can’t figure out if I can read if it has a tube in it or not , I know it is deleted and has 4” pipe all the way back, pretty much it does it any speed or time, today it did it as soon as I pulled out of my parking spot at work, during the week it went 4 days without popping up at all, I attached the picture of the 1 time I got the MAF code
 

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08lmm72mm

Active member
May 13, 2019
528
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Saskatchewan, Canada
Conditions for Setting the DTC

P0102

The ECM detects that the MAF sensor is less than 3.6 g/s for greater than 3 seconds.

DTC P0113


Intake Air Temperature (IAT) Sensor Circuit High Voltage

P0113 is open, short to voltage, or signal performance on the signal wire of the sensor

Circuit/System Description

The intake air temperature (IAT) sensor 1 is a variable resistor that measures the temperature of the air entering the engine. The engine control module (ECM) supplies 5 volts to the IAT signal circuit, and a ground for the IAT low reference circuit. The ECM continuously monitors the IAT sensor 1 signal voltage for an excessively high or low voltage.

Conditions for Running the DTC


The engine is running.
The DTCs run continuously when the above condition is met.
Conditions for Setting the DTC

P0112

The IAT Sensor 1 parameter is warmer than 148°C (299°F) for greater than 1 second. This is equal to or less than 0.10 volt on the IAT signal circuit as measured by the ECM.

P0113

The IAT Sensor 1 parameter is colder than -39°C (-38°F) for greater than 1 second. This is equal to greater than 4.8 volts on the IAT signal circuit as measured by the ECM.

Action Taken When the DTC Sets

DTC P0112 and P0113 are Type B DTCs.

Conditions for Clearing the DTC

DTC P0112 and P0113 are Type B DTCs.

Diagnostic Aids



With the ignition ON and the engine OFF, if the engine is cold, a properly functioning IAT sensor will gradually increase the scan tool IAT Sensor parameter. This is due to the heat that is generated by the mass air flow (MAF) sensor heating elements.
Depending on the ambient temperature, an IAT sensor signal circuit or low reference circuit that is shorted to the MAF sensor signal circuit can cause a DTC P0113 to set. This condition can cause a rapid fluctuation in the IAT Sensor parameter.
An IAT low reference circuit that is open can cause the IAT Sensor parameter response to be sluggish. This condition may not necessarily set a DTC.
An IAT sensor signal circuit that is shorted to the MAF sensor ignition circuit can cause a DTC P0113 to set.
Verify that any electrical aftermarket devices are properly connected and grounded. Refer to Checking Aftermarket Accessories.
Circuit/System Verification



Engine running, observe the scan tool IAT Sensor 1 parameter. The reading should be between -38 to +148°C (-36 to +298°F) depending on the current ambient temperature and the vehicle operating conditions.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing



Ignition OFF, disconnect the harness connector at the mass air flow MAF/IAT sensor.
Ignition OFF, for 90 seconds, test for less than 5 ohms between the IAT Sensor 1 low reference circuit terminal 4 and ground.

If greater than the specified range, test the IAT Sensor 1 low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

Ignition OFF, test for less than 5 ohms between the MAF sensor low reference circuit terminal 2 and ground.

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

Ignition ON, verify the scan tool IAT Sensor 1 parameter is less than -39°C (-38°F).

If warmer than the specified range, test the signal circuit terminal 5 for a short to ground. If the circuit tests normal, replace the ECM.

Install a 3A fused jumper wire between the signal circuit terminal 5 and a ground. Verify the scan tool IAT Sensor 1 parameter is warmer than 148°C (298°F).

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

If all circuits test normal, test or replace the MAF/IAT sensor.
Component Testing

Measure and record the resistance between the signal terminal 5 and the low reference circuit terminal 4 at the IAT sensor. Compare the value to the Temperature Vs Resistance table. Refer to Temperature Versus Resistance (EGR Temperature Sensors) Temperature Versus Resistance (ECT Sensors) Temperature Versus Resistance (Fuel Temperature Sensor) Temperature Versus Resistance (IAT Sensor 1) Temperature Vers.us Resistance (IAT Sensor 2) Temperature Versus Resistance (EGT Sensors).
 

Ron Nielson

Active member
Oct 11, 2009
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Berryton, KS
my MAF seems to be reading lower then every one says
One thing that can cause the MAF reading to be low is that the EGR valve is open at least more than it is supposed to be. Another cause is that the intake air tube is larger in diameter than stock which skews the MAF reading, such as an aftermarket intake.
 

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1FastBrick

Well-known member
Dec 1, 2016
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Junkyard
What doesn't make sense is it shows 99.6% throttle percentage but only 720rpm & 0.09lb/min of air.
Thinking 1 of 2 things.
The Chineseium scanner could have the wrong info or it's not translating it correctly. Even Snap Off has that issue from time to time.

Or could the pedal be bad? Seeing the wrong input and then interrupting the a miss match of what it should be seeing for that much TP%
 
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1FastBrick

Well-known member
Dec 1, 2016
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Junkyard
Wouldn't it Rev to the moon then while in park or neutral?
One would think so, But I don't have the schematics for how it works on that truck. I don't know on these trucks but some peddles have dual outputs that act like a fail safe.

It could also be bad data on the scanner. The Chinese scanners often copy other companies data with out under standing how to interpret it or verifying that is 100% functional and correct.
 

2004LB7

Well-known member
Dec 15, 2010
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Norcal
that throttle % is probably from the scanner looking at the wrong pid. if I'm not mistaken, there are two or three variable resistors in the peddle with one in reverse orientation to prevent full throttle if there was a short or failure in the peddle. it helps the ECM verify the validity of the peddle position. I'm pretty sure you can see all three (or two) in the efi live scan tool
 
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Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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Phoenix Az
has the throttle blade been disconnected or are the electrical plugs still plugged into it? its a known issue that if the truck is deleted and the throttle blade is still on the truck, the blade needs to be disconnected.