I am hot, can't see at night and can only go 10 miles per hour

Michael Mobile Technician Clinton, Utah Posted   Latest   Edited  
Tech Tip
2007 Chevrolet Avalanche 5.3L (LC9) 4-spd (4L60-E)
U0107 - Lost Communication With Throttle Actuator "A" Control Module

Got a call to a shop. They had a vehicle with a throttle actuator that would not work much of the time. The customer noticed that the lights got dim and the A/C went warm when the throttle acted up. They replaced the actuator control module on the firewall and had added some new grounds between battery, firewall and engine block. When I got there I worked to identify the issue. It was very bazzar. When the headlamps were on and the A/C going, the throttle would act up. When the A/C cycled, the headlamp would go dim. The easiest effected part to access was the headlamp. I monitored the ground side of the headlamp to see what was going on. When the A/C cycled on, the ground would read 3 volts. When it cycled back off, the voltage went to 0 volts. Obviously a ground issue. I looked at the wiring diagram and noticed that all of these grounds were tied together. The diagram I was looking at showed them connected to the rear of the cylinder head. In searching the area, no wire was found. I found a picture online and it showed the ground bolted to the front side of the drivers side cylinder head. My searches for a stray ground were futile. It appeared at one point that the engine had been replaced. There were some wires routed incorrectly and some broken plastics that made me think the engine had been out. The grounds could have been eliminated, connected in another area or severed. To save time, I decided to cut the ground wires and splice in leads, binding them to the front side of the driver side cylinder head, I used triple wall heatshrink and insulation free solderless connectors to make the fix. After clearing the codes, the engine started, ran and the throttle worked fine. Sorry, no pictures this time. Did not take time to snap pictures as I was running behind.

Dave Mobile Technician
Ironton, Ohio
Dave Default

Hey Michael , I was just called to do a no crank after engine replacement on a GM. The main computer grounds that were supposed to be on the block with the battery ground had been installed on the alternator output terminal. Got to love em.

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Sean Technician
Cincinnati, Ohio
Sean Default

I had one on a Malibu, customer did alternator and a starter and ran the alternator output to the ground side of the starter

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default

Once, just ONCE, I wish I could get a customer complaint that specific! :-) So I'm confused where you spliced, since the wires were totally missing. Right at the headlamp?

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Michael Mobile Technician
Clinton, Utah
Michael Default

Hi Geoff, I spliced one wire to headlamp, one to A/C Compressor and one to Throttle Body Controller. Cut the ground wires near each component and overlayed new wire. -Mike

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Tim Owner/Technician
Clovis, New Mexico
Tim Default

Thanks for sharing Mike!

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