Confirmed: Clearing codes re-enables Cruise Control

[RiverGuy]

At 99,000 miles, recently I started doing more frequent towing, including some extremely hot days >100 degrees here in Minnesota. Trailer weights under 3,000 lbs, but in some hilly areas. My check engine light has been coming on intermittently for several thousand miles complaining about a P0480 fan-clutch circuit, but local GM dealer hasn't been able to find the problem and says the fan-clutch is operating normally, so I can ignore that.
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Anyway, after towing a couple of hours on that VERY hot day, the cruise control stopped working. I thought it might have been one of the three fuses in the CC circuit or the brake light switch, so I checked all that out. No trouble found...so I was stumped.
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Then I read on another forum someone's suspicion that certain >>combinations<< of P-codes might cause the ECU to disable Cruise Control, though this is not found in the GM Factory Service Manuals, nor on AllDataDIY in any service bulletins. Sounded like an Urban Legend to me.
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Anyway, after following all the troubleshooting steps documented in the manual, I plugged in my Tech2...and along with the P0480 I found the following NEW codes: p1133, p0136, p0016, p0014. I hate clearing codes before fixing the underlying problem(s), but in this case clearing the codes brought the Cruise Control back to life!
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About a week later it happened again (again, while towing), and once again clearing the codes got the Cruise Control working again.
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Just thought I'd pass this along, as I can now confirm it's a real phenomenon. I am curious though as to what the engineers thought they were accomplishing by turning off Cruise Control in the presence of these codes...maybe as a Machiavellian trick to punish owners who ignore their check engine lights? >;-}

 

[Mooseman]

It is common knowledge here that certain codes will disable cruise control. I guess it's a form of persuasion for people to get it fixed.

As for the fan clutch codes, it is likely broken wires in the harness in the fan clutch.

P1481 error code clutch fan speed sensor fault

Hi all GMTNation. .I have a 03 gmc envoy 4.2 and I am getting a P1481 error code which is to due with the clutch fan speed sensor circuit malfunction. I had replaced my clutch fan a few years ago and everything was fine until recently I got this P1481 code but my clutch fan is still operating...

gmtnation.com

Better to get it fixed as it could make the engine go into reduced power mode as its 5v reference is shared with the throttle system's. Another option is to replace it with a thermal clutch from an 08-09 and have the codes deleted via a tune. If staying with the EV fan clutch, you should find an ACDelco/Behr original as the aftermatrket ones don't work within the specs. This is especially important if towing.

 

[RiverGuy]

Makes perfect sense, thanks!

 

[AmpOverload]

I don't own a Tech2, but some GM vehicles (including yours, IIUC) will report the reason why the cruise control is inhibited (or why it disengaged) for anywhere from 1 to 8 of the last cases. You might want to scan the Tech2 screens for that info because it could get you closer to the real reason for the CC problem.

This is a list of typical "reasons" but it is not specific to your vehicle and is probably incomplete:

• ABS
• ALDL
• B+ Volts
• Brake
• CC Cancel SW
• CC Inhibit Ckt.
• Clutch Switch
• Delta Vehicle Sp
• Eng Not Running
• Engine Speed
• Injector
• Low Spd 96A
• MPH Limit
• Man. Neutral CC
• P0751
• P0753
• P0756
• P0758
• P0785
• Park Brake Act.
• SMCC Fault
• Serial Comm
• TCS
• Trans.
• Veh Spd
• Veh Spd Fault

Hope that helps!

 

[AmpOverload]

I remembered this thread just now as I was playing around with my new VCX Nano and Tech2Win, viewing "Cruise Control" data and simulating various "disengage reasons".

So I re-ran Tech2Win, selecting options appropriate for the OP's vehicle (a 2004 Oldsmobile Bravada, IIUC), and I got to this Tech2Win "Data Display" screen:



Selecting 'F7' brings up a "Cruise Control Data" screen showing 8 "Cruise Disengage # History" lines, one for each of the last 8 times the cruise control disengaged, giving a "reason" for each case:



In that screenshot, I'm simulating the first 8 possible reasons for the disengagement, but the first 2 cases just happen to be the same: "Brake".

In these next 2 screenshots, I'm simulating the next 16 possible "disengage reasons" (8 per screen), just to give folks an idea of some of the other possibilities for CC disengagement:



BTW, on the Buicks on which I typically test, only the very last CC disengage reason is given, not 8. Furthermore, the meanings assigned to the "reason" codes are substantially different! The list in my previous post in this thread is accurate for a 2004 Buick Century, but not at all for a 2004 Oldsmobile Bravada!

Anyway, I hope this info helps someone out in the future who might run across this thread and owns a Tech2 or can run Tech2Win.