BurbinMomma

I have a 2007 Suburban 5.3 Flex Z71- I've not had working cruise in almost 4 years. I got PO121 & PO455 codes as well. The PO121 was resolved by replacing the Throttle Position Sensor (TPS). Several forums said you have to change the entire throttle body, but that's not true. We cleaned the throttle body & replaced the TPS, cleared the code & it's resolved.
The PO455 code is my current project. It can sometimes be the gas cap (check that it's seated properly, clean & fully clicked in place first), but it actually indicates an EVAP system large leak which can also be the vent valve canister (my issue). Here's the info from the PO449 & PO455 thread that I got my part numbers from:
GM # 20995472 - EVAP canister vent/valve/hoses/filter assembly= $71.96
GM # 19257603 - Electricaladapter/harness = $30.14
You need the adapter because the new and old electrical connections are different. It's about 6 inches long.
I ordered the wiring harness from Amazon for $10 & the EVAP canister from AA for $72 including tax.
If it is the EVAP canister, it's easy to get to & there is plenty of info on the above mentioned thread

penzfan

The Cruise on my 06 Sub stopped working a few days ago. The green CC light on the dash does not come on and the cruise does not engage when I push the button. Fuse is fine and I replaced the Brake Light Switch today. Still not working. Any other ideas?

BurbinMomma

I would start by changing the Stop lamp switch as I mentioned in my post above. It takes a 10mm wrench and a bit of flexibility (put the driver's seat as far back as you can & put something outside the door to sit on). It's actually very easy to change & immediately fixed my issue. The part was $10-15 on Amazon. I tend to start with least expensive parts and work my way up while diagnosing issues.

penzfan

Ive already replaced the Brake Light/Stop Lamp Switch attached to the brake pedal. Still not working. Next?

a55bruce

Did you check all these fuses:
Instrument panel fuse block: VEH STOP, CRUISE
Under hood fuse block: ETC/ECM, STOP LP
If they are OK, then I'd check the connector to the Throttle Actuator Control Module.

Dennis Schwinn

Help I've replaced the brake light switch make sure all my brake lights work including the third light even change the steering wheel controls I get light on steering wheel but no engagement of cruise control where would I look next

penzfan

If the TACM is bad wouldn't that effect the accelerator operation also? And wouldn't I have a code showing up? Thanks

Triplegfit

This forum help me fix my cruise control problem I’ve had for 3 years. Checked fuses did everything to try figure it out. Come to find out from this from it just took replacing the (Break Light Switch) problem I had was the light on the steering wheel turned on but did not engage. Fixed the problem right away. Found the part at AUTOZONE for $21.17
id recommend looking up YouTube video to replacing it to help you remove it and installing without breaking it.