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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29457
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I was pulled over yesterday and my speedometer reading is

Customer Question

i was pulled over for speeding yesterday and my speedometer reading is only at 35 but my suburban could not even run fast because the engine light comes on and reduced engine speed appeared in my dashboard while i was driving yesterday. how did this happen?
JA: Thanks. Can you give me any more details about your issue?
Customer: i was driving my suburban yesterday and the check engine light comes on and reduced engine speed and my car could not accelerate
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Submitted: 1 year ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 1 year ago.

Hi there, I am Cam.
Can I get your first name please?
I am not sure if you have used our service before or not. The experts here are third party contractors. Myself, I am a GM technician in a Gm dealership. I will be happy to help you. Please understand that my only compensation for the time spent helping you is by your rating of my service in a positive way. The more information you provide, the better the chances of getting your issue resolved. Also please reply if you have any followup questions.
So about your vehicle,

What year is your Suburban?

Customer: replied 1 year ago.
Christine, chevy 03 suburban
Expert:  GM Tech (Cam) replied 1 year ago.

OK, does the speedo stick at a speed faster than what you are actually doing?
The check engine light, what does are being set?

I have ideas for both, but I am not sure if you have one problem or 2.
For the reduced engine power, here is the common thing.
These years of trucks with the electric throttle have a couple of very common issues. First and in my experience most common is the ground wire. THe ground runs from the rear harness behind the top of the engine to the rear of the left cylinder head. It is attached at the same bolt as the ground strap at the firewall. I have always been able to find this by pulling on the black wire and see if it gives. The fault has been a conductor broken in the insulation at the crimp. The second issue is the wiring near the throttle body. The wiring tends to break a few inches from the connector. check these out and see. Another common issue is the wiring near the throttle body itself. There are some wires there that can break inside the insulation and cause this. Check the wiring carefully near the throttle and about 6" back.
Also check the wiring at the pedal under the dash, micro corrosion in the connectors can cause issues and even unplugging and plugging the connector back in will correct, it so then put some electronics grease on the pins. Finally is a connector in the throttle body itself. It is common for the pins in the connector to fail and cause codes. The repair for this is the pigtail connector for that throttle body.

For the speedo, This is a failure of the stepper motors that physically move the needles in the cluster. When they fail, the needle may be erratic, not move or read wrong. The repair options are to replace the whole assembly, or repair yours. Replaceing the whole assembly is not a good option as it is very expensive. This is what most shops will do.
Repair of your unit will cost about 100 and you can send it out yourself.
The place I recommend for repair is They will repair your cluster and send it back.
You can remove it and drive without the cluster for a short time while it is out.

Customer: replied 1 year ago.
The throttle body was replaced a few months back
Expert:  GM Tech (Cam) replied 1 year ago.

Ok, but there are several other points of the throttle issue, the throttle body honestly being the least likely. read through and follow what I mentioned.

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