2000 LS-1 Cruise Control Intermittent

Had that happen after i hit uneven bump in the road. My dealer than adjusted it.

The car or the bump? Has anyone seen a even bump ? ;-)

Quoth snipped-for-privacy@webtv.net (R B S) in news:24944-3F5FC06C-106@storefull-

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,

Tom Betz wrote:

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.

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 snipped-for-privacy@webtv.net (R B S) in news:24944-3F5FC06C-106@storefull-

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)

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.

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 snipped-for-privacy@webtv.net (R B S) in news:24944-3F5FC06C-106@storefull-

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...

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.

Quoth J Swain on Tue, 16 Sep 2003 01:38:21 GMT:

We finally got ours fixed when we took it in for inspection this week, and found that one brake light was out. Though I don't have the diagnostic codes on the invoice (and my wife, who took the car in, didn't ask for them) they ended up replacing the passenger side taillight assembly on ours, as well. No SES in our case, but it looks like we had the same corroded socket problem you had as the root of our problem.

I wonder how common this problem is in these cars...