Yesterday, the cruise control in our 2000 LS-1 (4-banger with automatic) became intermittent. The on-off switch lights properly, the Resume/Set switch seems to work normally -- it doesn't feel broken -- but from time to time, it will just kick out of cruise, even though I have not tapped the brake or touched a switch, or even turned the steering wheel much (on a long interstate straightaway). Then it will start working for a while, often after having stopped somewhere and started it up again, only to stop working suddenly. Is this a known problem with this vehicle, or are we going to have to play diagnostic games between the various sensors and switches and computers involved in managing cruise control? Thanks.
Quoth (R B S) in 2332.public.lawson.webtv.net: Thanks for the info. In this case, it happened on absolutely smooth road, but I'll bring it to their attention. Interestingly, this was not a problem before the recall service...
I just had my car in because the cruise control wouldn't work when I had my headlights on....replacing a corroded socket in the rear brake lights was the fix...how is that related(electrically, of course), but how??? Also, SES light and Service/Wrench light came on and diagnostic codes were P01511, 571, 172 (exactly as written on work order). Can any one decode those? Thanks, 2001 LW300 owner
One way that the cruise control can tell if you put your brakes on is by monitoring the voltage going to the brake light bulbs. If it isn't very near zero, then you're pressing on the break pedal. The tail light bulbs have two filaments and a common ground. If you have the tail lights on, the current goes into the (lower wattage) filament and to ground. If the ground terminal is corroded, the current goes into the lower wattage filament, skips the broken ground connection, and goes through the other (brake light) filament of that bulb. It then travels to the OTHER filaments in OTHER brake light bulbs to ground. Now, if the cruise control is monitoring the brake light voltage, this corroded ground will cause the voltage to go up (maybe only a volt or so) when the lights are on. If it's sensitive (read: incorrectly designed) it will deem this to be due to you putting on the brake and will disengage. I hope you paid attention - there WILL be a quiz next period. I just had my car in because the cruise control wouldn't work when I had my headlights on....replacing a corroded socket in the rear brake lights was the fix...how is that related(electrically, of course), but how??? Also, SES light and Service/Wrench light came on and diagnostic codes were P01511, 571, 172 (exactly as written on work order). Can any one decode those? Thanks, 2001 LW300 owner Tom Betz wrote: Quoth (R B S) in 2332.public.lawson.webtv.net: Had that happen after i hit uneven bump in the road. My dealer than adjusted it. Thanks for the info. In this case, it happened on absolutely smooth road, but I'll bring it to their attention. Interestingly, this was not a problem before the recall service...
....wait until my Tylenol kicks in, re: quiz Geesch, engineers - you can't take 'em anywhere!! (smile) One way that the cruise control can tell if you put your brakes on is by monitoring the voltage going to the brake light bulbs. If it isn't very near zero, then you're pressing on the break pedal. The tail light bulbs have two filaments and a common ground. If you have the tail lights on, the current goes into the (lower wattage) filament and to ground. If the ground terminal is corroded, the current goes into the lower wattage filament, skips the broken ground connection, and goes through the other (brake light) filament of that bulb. It then travels to the OTHER filaments in OTHER brake light bulbs to ground. Now, if the cruise control is monitoring the brake light voltage, this corroded ground will cause the voltage to go up (maybe only a volt or so) when the lights are on. If it's sensitive (read: incorrectly designed) it will deem this to be due to you putting on the brake and will disengage. I hope you paid attention - there WILL be a quiz next period. I just had my car in because the cruise control wouldn't work when I had my headlights on....replacing a corroded socket in the rear brake lights was the fix...how is that related(electrically, of course), but how??? Also, SES light and Service/Wrench light came on and diagnostic codes were P01511, 571, 172 (exactly as written on work order). Can any one decode those? Thanks, 2001 LW300 owner Tom Betz wrote: Quoth (R B S) in 2332.public.lawson.webtv.net: Had that happen after i hit uneven bump in the road. My dealer than adjusted it. Thanks for the info. In this case, it happened on absolutely smooth road, but I'll bring it to their attention. Interestingly, this was not a problem before the recall service...
Thanks...forgot about the brakes disengaging the CC, but agree that a design that uses some measurement off the brake lights is not ideal....
This car has an Electronic Throttle Control system where the throttle plate on the engine is controlled by a motor instead of being physically connected to the gas pedal. Code P1511 indicates that the detected throttle position was outside a range of 3.7 to 9.8 percent when the ECM was in Reduced Performance mode, the car was stopped and the accelerator pedal position was less than 15%. Code P0172 indicates that the engine's fuel trim is below a certain limit in the negative direction, indicating that the engine is tending towards running too rich, and that based on the oxygen sensor, the ECM is having to subtract fuel from what the other sensors indicate the engine should need. It's possible that both of these are caused by a bad throttle position sensor, though other causes are possible. There are two inputs to the ECM from the brake pedal, the cruise brake switch and the stop lamp switch. Code P0571 indicates that the ECM detected that for 20 consecutive times, one changed state but the other did not. Likely, this means that one of the switches is bad.
