Trailblazer engine replacement riddle

Lovelessnate

Original poster
Member
Dec 15, 2020
2
Paducah ky
I have an 06 trailblazer LS 4.2 4x4 and have swapped the engine from a 2007. Every since completing the swap I have been stuck in power down mode. After taking it 2 mechanics and a gm dealer I was told that the computer was bad. I replaced the computer with a new unit programmed to the vin of my 06. I used my original 06 wiring harness and noticed a couple differences on the accessories so I just swapped my original accessories to the new engine. I keep throwing codes for throttle body voltage to low. I have replaced the throttle body, accelerator pedal, mass air flow sensor. I am thinking of replacing the engine harness but my gut tells me there is something more to it than that. Where there any changes between 06-07 that would cause these issues for mixing the years computers and harness? Any help will definitely be appreciated.
 

northcreek

Member
Jan 15, 2012
3,310
WNY
Perhaps your voltage is too low. There appears to be a difference in alternators between 06&07 and if you've done changes there, it might be worth a look.
 

mrrsm

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Oct 22, 2015
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Unfortunately... the GM Engineers decided to knit the Fan Clutch 5 Volt Low Voltage Reference Circuit into the same ones that ACC Pedal and Throttle Body share... so while this is VERY remotely possible... if your Wire Bundle leading along the Engine Compartment to and from the Fan Clutch Harness Connector (Purple Rectangular)....Near the Driver's Side Radiator Fan Housing, along with the Wiring nested inside of the Black Tube has either been Shorted, Cut or Compromised, they might interfere with the Class 2 Network interaction in between the MAF Sensor, the Hi-Lo ACC Pedal Response and The Throttle Body and prompt a Reduced Engine Power (REP) condition. Try unplugging THAT connector and see if you get any better response.

Note:

Because of an earlier history involving "Runaway Engine Conditions" , GM altered the PCM programming to be especially sensitive to regulating EXACTLY how much Air is getting ingested into the Engine, moment by moment.

The loss of or interference with the Control Signal coming either to or from the MAF Sensor, the Throttle Body or the ACC Pedal will prompt the PCM to Automatically Default to a Reduced Engine Power condition ...for the Sake of Safety.
 
Last edited:

Lovelessnate

Original poster
Member
Dec 15, 2020
2
Paducah ky
Perhaps your voltage is too low. There appears to be a difference in alternators between 06&07 and if you've done changes there, it might be worth a look.
If my memory serves me correctly the alternator was one of the accessories I had to keep off my 06 engine due to the 07 engines alternator having a 3rd wire and my two wire harness wasn’t compatible with the 07
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Unfortunately... the GM Engineers decided to knit the Fan Clutch 5 Volt Low Voltage Reference Circuit into the same ones that ACC Pedal and Throttle Body share... so while this is VERY remotely possible... if your Wire Bundle leading along the Engine Compartment to and from the Fan Clutch Harness Connector (Purple Rectangular)....Near the Driver's Side Radiator Fan Housing, along with the Wiring nested inside of the Black Tube has either been Shorted, Cut or Compromised, they might interfere with the Class 2 Network interaction in between the MAF Sensor, the Hi-Lo ACC Pedal Response and The Throttle Body and prompt a Reduced Engine Power (REP) condition.

Try unplugging THAT connector and see if you get any better response.
:iagree: :iagree: :iagree: :iagree: :iagree: :iagree: :iagree: :iagree: :iagree: :iagree: :iagree:
 
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mrrsm

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Look in the Upper Right Hand Corner of the GMTN Screen...and *Click* on the Envelope Icon
 

Mooseman

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Or just hover over his avatar or name and an option will pop up to Start Conversation.
 
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