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Eric
Eric, Automotive Repair Shop Manager
Category: Chevy
Satisfied Customers: 32082
Experience:  20+ yrs. experience as repair shop manager and technician.
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I reset the computer bc of a check engine light and it wont

Customer Question

i reset the computer bc of a check engine light and it wont clear codes. i can only get 5 out of 8 to complete
JA: Does the light stay on, or does it blink?
Customer: nothing comes up as anything wrong the machine says no problems no engine light nothing just wont finish completing codes
JA: What is the model/year of your Chevy?
Customer: 2005 uplander
JA: Are you fixing your Uplander yourself? What have you tried so far?
Customer: no my mechanic tried everything they could think of and they ran out of ideas they even gave me their machine to plug in everytime i shut van off and still nothing
JA: Anything else you want the mechanic to know before I connect you?
Customer: the replaced sensor reset codes 3 times and we even unplugged the battery for a day drove it still only completes 5
Submitted: 7 months ago.
Category: Chevy
Expert:  Eric replied 7 months ago.

Hi,

Ok, I assume you mean the monitors such as O2, EGR, Catalytic converter, etc.

This requires a precise drive cycle to be performed. This should be done with 1/4 to 3/4 tank of fuel and after having sat overnight for at least 8 hours

General Motors Driving Cycle

A complete driving cycle should perform diagnostics on all systems. A complete driving cycle can be done in under fifteen minutes.

To perform an OBDII Driving cycle do the following:

Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.
Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.
Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.

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Expert:  Eric replied 7 months ago.

I noticed we have not yet resolved your concern you asked about. I would sure appreciate it if you would reply so I can offer my skills and knowledge and repair guide access to help as best I can.
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Expert:  Eric replied 7 months ago.

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