View Full Version : New issue. Dealer cant figure it out.

10-08-07, 03:33 PM
I have an 05 V. Took it on a road trip to visit family. Noticed the cruise control wont stay on. Hit a small bump in the road, or anything small, the cruise turns off. Not a big deal. Then as i exit to get gas, taking my foot off the gas, the whole car surges like the engine is dead. Big time driveline slack. same thing when I shift. I take it to my dealer, they replace the motor mount on the left side, and no joy. Still does it, and then cant find out whats wrong. I dont know if the cruise control and the huge clunk is related, but the car is undriveable. I am afraid of doing more harm if I drive it. I have had 4 (four) read ends, rebuilt tranny, new radio and motor mounts. I love the car, but the warranty is running out and I cant rely on the car anymore. Any ideas to help my dealer fix the issue? BTW, my dealer is been very nice and I would recommend them to anyone in the Chicago area.

As far as a replacement car, I think my only options are 2008 CTS (AWD) or BMW 335ix. I dont like Audi or Mercedes. Any opinions there? I need a car that doesnt scare me in the snow and is somewhat quick.

Sorry for the long post.

Cadillac Tony
10-08-07, 03:44 PM
Ask them to check the clutch position switch and the wiring going to it. If the wiring is pinched/chafed or the switch is bad, the car will think the clutch is in and cut your cruise off.

I'm not sure about the surge/cutout when letting off the gas- sounds sort of like a Throttle Body issue. Again, have them check the wiring and/or diagnose the TB.

10-08-07, 03:57 PM
I just had a problem with my Cruise control not working. I had Onstar do a diagnostic (and the Dealer confirmed) that when there is any problem with the drivetrain the Cruise is disabled.

Have them check the Transmission.


10-08-07, 03:59 PM
They tell me now that they cant reproduce the issue. I have to go there after work and see if it "magically" fixed, or if they are going to call the issue normal.

I will mention the clutch switch (kinda my thought). I would think that they did a diagnostic on the car, but I will ask.

thanks for the replies.

10-16-07, 04:32 PM
mechanic worked on it again. Replaced 2 rear knuckles, and the diff (this is my 5th). Still does it. They say the clutch may be going with 46k on it. Wont work on it anymore. It does the bucking only when the car warms up. under light throttle or shifting, the bucking is so severe. I am going to clean the MAF tonight. Otherwise I am out of ideas. I dont think its the clutch since it does it in gear???

The Tony Show
10-16-07, 04:41 PM
As far as the cruise issue, only a problem that the PCM can see would cause the cruise to not work. A problem with the diff, knuckles or clutch wouldn't be picked up by the PCM, so it can't be that. A drivetrain problem bad enough to disable the cruise should set a check engine light anyway. It's either the clutch switch or wiring, I'm sure of it. If the car thinks the clutch pedal is pressed then the cruise won't work.

The bucking and surging could be a lot of different things, but the MAF is a good place to start. Be sure to pick up a can of MAF cleaner at the parts store- DO NOT use WD-40, brake cleaner, or anything else not designed for a MAF sensor. Also be sure to avoid dropping or jarring the sensor, and don't touch or spray high pressure onto the elements inside as they're very brittle.

10-16-07, 04:44 PM
Thank you for the info. What about the Throttle by wire soleniod? Do those ever go bad? Kinda makes sense to me that if the throttle is loose or not returning to the place the computer thinks its going, could cause low throttle/no throttle issues?? Just a random thought.

The Tony Show
10-16-07, 04:49 PM
A member on another forum had this same problem- here is what his Repair Order from the Dealer said:

--- Check and run system Diagnnosis Check No codes Stored Run Diagnosis Chart For Cruise Inop And found clutch pedal signal Applied all the time Check power to clutch switch ok But no power to ecm Trace wireing and found broken wires in engine compartment At connector 105 Replaced Terminals and repair wiring retest all ok

4 12034046 Terminal $3.71
1 242 W Wire $0.95
2 19168448 Splice Kit $11.91

Don't know if that's helpful or not, but it might give your guys someplace to start looking.

10-16-07, 05:31 PM
Nice find, Tony. :thumbsup: Hopefully, that's it!

That Tony is such a good guy.

C "T" ess
10-16-07, 05:56 PM
Check the power brake booster using a soapy water mixture. A leak in the unit will affect the cruise control which could also cause your engine problem. Another idea is to check the IAC mounted on the throttle body. Take it off and clean the metering valve. This was a rather common proble on the Corvette. That's the basic engine package in your car.
As a last resort, have someone check the PCM for issues or reflash the memory with the latest download.

10-16-07, 09:42 PM
On a whim I pulled the "comp clutch" and "htr vlve/cltch" fuses. Problem went totally away. Cruise control doesnt work at all and the car wont start with the fuses pulled. So its a wiring/electrical issue, not a mechanical one. Going to call the dealer in the morning. Anyone know what the difference is in the 2 fuses?

And thanks for the help narrowing this down. Lots of help from the forums and everyone.

The Tony Show
10-16-07, 10:15 PM
Your first post indicated you're still under warranty. My advice is to stop tinkering and let the dealer fix it.

Have them trace the wiring for the clutch pedal sensor and find where it's broken.

10-16-07, 10:34 PM
And to not confuse future people searching...The V (or Z06s for that matter) do not have an IAC.

10-24-07, 11:55 AM
I think the cruise control issue is related to the PCM not "reading" the clutch position correctly. The dealer replaced the clutch sensor and it seemed to help a little. Now, the issue doesnt show up until the car has been driven for about 15-20 minutes. So the dealer is ordering a new PCM. But of course its on backorder. So I have to wait until it comes in. The dealer said if that doesnt fix it, they will have GM engineers look at it.

BTW, I got a new DTS for a free rental. Its a decent car, but the interior needs some work. Way too bland. Love how the engine sounds though.

The Tony Show
10-24-07, 12:07 PM
I hope they're not surprised when the new PCM can't read the clutch position through the broken connection either.

Throwing parts at a car until it stops acting up- gotta love it.

10-24-07, 11:12 PM
Let me get this straight, you've blown 4 rear ends, a tranny, motor mounts and your warranty is about to expire. It sounds like you've had big troubles with that car and could be facing many Thousands of Dollars in repairs in the near future. Why haven't you extended the warranty? I'm confused.