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2003 GMC Yukon XL. Multiple codes any help appreciated!!


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I Have a 2003 GMC Yukon XL 5.3  my beater the check engine light has been on for about a week, so went and had codes read in picture attached. I am wondering where I should start with this issue, should I just order a new plug and play ecm, or where to start looking for wiring issues.

 

Codes as listed

p0420 Catalyst system bank 1

p0101 mass air flow circuit Range/ Preformance

p0118 engine coolant temp high input

Repeats codes in the same order once. 
Advice greatly appreciated!!

 

7A83C67E-9840-4F27-A162-2742124D8054.jpeg

4B29FAD6-FE98-454B-9C2F-A735E1803555.jpeg

EC170E8B-4410-4CD1-906E-B024B2065D6C.jpeg

54C50769-98D0-4189-A5C2-3EB4D54F87CD.jpeg

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unplugged the maf looked at the connection didn’t seem to be dirty but I will by take it apart clean the sensor it’s self and see if that helps. Also forgot to mention has a starting issue but only if say I shut it off for a short period of time and then it cranks longer than it should  stumbles for a few seconds then runs fine.

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Ok so I went to orilleys today to get maf cleaner bought it went out to leave tried to start the Yukon cranked would not start, and some how triggered the security light. Later got it to my buddy’s shop where I cleaned the maf as well as read and cleared codes using snap on scanner So far both maf, and oxygen codes have not came back up and my check engine light has stayed off. Got home shut of left it alone for 10 min tried to start cranked three times stumbles and start then runs fine. So got the scanner back manually controlled the fuel pump and on a hard start as explained earlier with the pump turned on and running dose not help. Which leads me to think my fuel pump is going bad Right?? If so which pump do you guys recommend? Thanks!!

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