Codes P1275 and P1280, starts hard but will idle?

Tiny
HUNTER0307
  • MEMBER
  • 2003 CHEVROLET TRAILBLAZER
  • 4.2L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 228,000 MILES
I replaced the valve cover gasket, intake manifold gasket, throttle body gasket, cleaned throttle body while out, I actuated the throttle body by hand while cleaning, put everything back together. Now it starts after the third try, it will idle at about 1,100 RPMs, no throttle response. I have p1275 and p1280 codes, check Eng and reduced power lights on. I have checked and rechecked all connections, run electrical tests, I cannot find an issue.
Monday, August 19th, 2024 AT 6:56 PM

10 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

Both codes are related to the accelerator pedal position switch in the vehicle. Was any work done to that?

Do me a favor. I attached diagnostics for the P1280 below. I feel that code should be checked first. Take a look through the diagnostics and let me know if you are comfortable performing them.

Let me know.

Joe

See pics below.
Images (Click to make bigger)
Thumb
Thumb
Thumb
Thumb
Was this
answer
helpful?
Yes
No
Monday, August 19th, 2024 AT 8:02 PM
Tiny
HUNTER0307
  • MEMBER
  • 11 POSTS
No work was done to the interior at all, I have a Foxwell scan tool, I am comfortable with testing, and will get back tomorrow.
Was this
answer
helpful?
Yes
No
Monday, August 19th, 2024 AT 8:09 PM
Tiny
HUNTER0307
  • MEMBER
  • 11 POSTS
I forgot to mention it will start and immediately stall 3 times then start and idle at 1,100 RPMs, but nothing on throttle.
Was this
answer
helpful?
Yes
No
Monday, August 19th, 2024 AT 9:57 PM
Tiny
HUNTER0307
  • MEMBER
  • 11 POSTS
I did all the tests, then tested the to unit with an ohm meter, 0.00 across all test, no response on meter when actuating throttle.
Was this
answer
helpful?
Yes
No
Tuesday, August 20th, 2024 AT 10:04 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

When you opened the throttle plate by hand, that may have damaged the throttle body. If you are getting no response or readings from testing, that is what it sounds like happened.

Let me know your thoughts.

Joe
Was this
answer
helpful?
Yes
No
Tuesday, August 20th, 2024 AT 5:49 PM
Tiny
HUNTER0307
  • MEMBER
  • 11 POSTS
Well, I replaced the throttle body with a known good one, no difference, my scanner says my throttle is not actuating, put old throttle body on another blazer and it ran perfect, I did the graph on my scanner for "absolute throttle position", got no response, flat line while I operated the throttle, I then did an ohms test on the throttle, and everything seemed good, I think I will still try replacing the throttle, still getting p1275, and p1280 codes, and refuses to reset, I have checked all vacuum hoses, wires, cant find a thing.
Was this
answer
helpful?
Yes
No
Tuesday, August 20th, 2024 AT 7:21 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
My online manual is presently down. However, I need you to check grounds for the TB and APP. See if anything was damaged or shorted.

Let me know.

Joe
Was this
answer
helpful?
Yes
No
Tuesday, August 20th, 2024 AT 7:32 PM
Tiny
HUNTER0307
  • MEMBER
  • 11 POSTS
Okay, I will get back. Also, I am going to be getting my vehicle inspection license, where might I find a good source on vehicle specifications like ball joint tolerance etc, for vehicles up to 2022?
Was this
answer
helpful?
Yes
No
Tuesday, August 20th, 2024 AT 8:37 PM
Tiny
HUNTER0307
  • MEMBER
  • 11 POSTS
Problem solved, thank you for all your help, attached picture of issue.
Image (Click to make bigger)
Thumb
Was this
answer
helpful?
Yes
No
Wednesday, August 21st, 2024 AT 6:58 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

It was a ground??? If so, I'm glad you found it. Electrical issues can be a pain. LOL

As far as your question about specifications is concerned, yes, I would be happy to get what you need. I just need you to start a new question when the topic changes or the vehicle changes. It is more helpful to others when that is done.

Here is the link to start a new one:

https://www.2carpros.com/questions/new

Regardless, I'm glad to know the problem is resolved. Take care and feel free to come back any time in the future.

Joe
Was this
answer
helpful?
Yes
No
Wednesday, August 21st, 2024 AT 7:13 PM

Please login or register to post a reply.

Related Engine Hard To Start Content

Hard Starting
GUIDE
Hard Starting
Pop­u­lar Hard Start­ing Causes
VIEW MORE