Dtc P0128 code info - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat

2000-2005 Discuss your 2000-2005 Bonneville SE, SLE, and SSEi Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

Thread Tools Search this Thread
Old 05-30-2004, 01:41 AM   #1
Senior Member
True Car Nut
Thread Starter
Join Date: Jun 2003
Location: Purgatory
Posts: 6,313
Thanks: 0
Thanked 0 Times in 0 Posts
PontiacDad is on a distinguished road
Default Dtc P0128 code info

Last weekend I changed out my thermostat from the stock to my 180 drilled. Last year I used this t'stat without problems but changed it out for the winter (I live in the far north). About 3 days later my ses light came on, p0128 thermostat malfunction, I reset the code and it never came back. I have been wondering why the code was set so soon after the swap?
The new pcm I have comming from intense will take care of this but why no problems last year and so soon this?

I had the cooling system flushed last fall and the coolant level is good.
PontiacDad is offline   Reply With Quote
Old 05-30-2004, 12:26 PM   #2
Join Date: Aug 2002
Location: Purgatory
Posts: 0
Thanks: 0
Thanked 0 Times in 0 Posts
BadSSEi is on a distinguished road

This is a DTC that only sets after two or three (can't remember which) driving cyles where the PCM detects an issue. So if you're too cold one time, then OK the next time, the counter resets. This is why most people won't see this code for several days or even a week after installing a colder thermostat.

Most people are actually fine with a 180, but a 160 will trip this code on new Bonnevilles pretty quickly.

Hope this helps.

BadSSEi is offline   Reply With Quote
Old 09-08-2005, 11:55 PM   #3
Senior Member
Posts like a Supercharger
Join Date: Jun 2005
Location: Saint Charles, MO (outside STL)
Posts: 174
Thanks: 0
Thanked 0 Times in 0 Posts
zuluhead is on a distinguished road

I've got a 180 in mine and just recently with the weather cooling off I've been getting this code. I haven't gotten an Intense PCM yet, would getting one of those take care of this? What are the chances that the coolant temp sensor has actually gone bad. The guage registers between 150 and 200 depending on time of day, so I'm presuming it'* working. Any ideas on how to keep this code from popping up?
zuluhead is offline   Reply With Quote

Related Topics
Thread Thread Starter Forum Replies Last Post
p0128 code symptoms parker2129 Chevrolet 6 07-28-2015 06:31 AM
More findings-FIXED!! - 93 SSE: DTC (Code) 42 & DTC 18 93RedSled-SSE 1992-1999 45 04-21-2008 03:21 PM
Code P0128 87National 2000-2005 1 02-26-2008 01:04 AM
Check Engine Code p0128 dally1up 2000-2005 6 12-16-2007 10:15 PM
Code P0128 and P0440 zuluhead 2000-2005 10 09-19-2005 01:20 AM

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT -4. The time now is 08:23 AM.

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.