2008 Pontiac Grand Prix - Code 128 Fixed

[wfo44]

have code 128 ran test and passed , cleared code and returned 2 days later, any info would be great

[VCAC239]

A PO128 should be an "insufficient Temp" code. Perhaps it's an intermittent T-stat issue. I would remove & replace with an OEM T-stat & see what you have after that.

Jeremy

[timjlive]

I would agree. Every P0128 I have encountered, ended up being the thermostat. Not that you should shortcut the diagnostic process but that's what I have run into. I would just verify the CTS reading with a temp gun to make sure the CTS is accurate. If that's good, it gets a stat.

[steven kiser]

i've been running into sensor issue a bit on gm's lately. like stated above check cts reading for the pcm through scanner.

[wfo44]

checked against temp gun and cts pulled t stat stuck open thanks yall