Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!

Ol fault

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6 years 2 weeks ago #20280 by autojoe
Ol fault was created by autojoe
Can someone tell me what is the enabling criteria for open loop fault to set? Gm with po300, po135. Thanks in advance. Joe

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6 years 2 weeks ago #20282 by Tyler
Replied by Tyler on topic Ol fault
We'd need to know more about the specific vehicle. Year/make/model/engine?

P0135 is for the B1S1 O2 heater circuit, I believe. I don't know the criteria off the top of my head, but I'd be surprised if the PCM commanded Open Loop for that fault alone. It's more likely the result of a misfire, IMO. Is there a noticeable misfire before Open Loop kicks in?

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6 years 2 weeks ago #20283 by autojoe
Replied by autojoe on topic Ol fault
2009 Silverado 5.3

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6 years 2 weeks ago #20284 by autojoe
Replied by autojoe on topic Ol fault
Yes and fuel trims go to zero then ol fault.

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6 years 2 weeks ago #20289 by Tyler
Replied by Tyler on topic Ol fault
Definitely sounds like it's responding to a severe misfire. :( Does it also misfire at idle? A power balance test might illuminate a weak cylinder.

What's the 8th digit of the VIN? Trying to see if this is the infamous LC9 engine.

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